Industrial Brake Motor Selection for Thailand Factories: Torque, Power Loss and FAT

When upgrading equipment or launching a new production line in a plant in Thailand, selecting a brake motor is often more difficult than selecting a standard motor. This article organizes the selection of industrial brake motors from the viewpoint of RFP creation and purchasing negotiations, so it can be used as a practical checklist at the plant.

1 Separate “stopping” from “holding” when selecting industrial brake motors

At the design and quotation stage, it is critical to clearly separate:

• the function of “stopping something that is moving”, and
• the function of “holding something that is stationary”.

If you leave this point vague and select a brake motor only by looking at the catalog braking torque, it becomes much more likely that the following problems will appear later in the project:

• Unexpected stopping distance
• Unexpected wear and high‑frequency maintenance
• Overload or overvoltage trips on the inverter (drive)
• Unanticipated risks of load dropping or reverse rotation

In the calculation procedure for geared motors from SEW‑EURODRIVE (Germany),

“static torque (holding)” and “dynamic braking work (stopping motion)” are calculated separately, and several additional checks are combined, including stopping distance, emergency stop load, inverter current, and verification of the regenerative resistor. According to the SEW‑EURODRIVE DRN.. calculation process, motor brake selection is considered essential, especially for vertical loads such as hoisting applications.

Reflecting this “functional separation” directly in your RFP and specification documents will make it easier to compare suppliers’ responses.

Organize the three aspects: “stopping”, “holding”, and “safety”

In industrial equipment, at least the following three types of “brake‑like” functions coexist. Because their roles and design bases differ, they must be described clearly and separately in the specification.

1. Motor‑integrated brake (brake built into the brake motor)

– In general, most are “power‑off type” brakes: a spring presses friction plates to hold the load, and energizing the coil releases the brake.

– As a representative example, Lenze/INTORQ spring‑applied brakes use spring force to generate friction torque and release the brake by coil excitation. The manual explains that the static torque is for holding when there is no relative rotation, and that performing an emergency stop while rotating increases friction work and wear. See Lenze/INTORQ BFK468 Operating Instructions.

– Main uses: holding the load in case of power failure, static holding after frequent positioning, etc.

1. Inverter regenerative braking (electrical braking including the resistor)

– The rotating motor is used as a generator; its energy is returned to the DC link and, when necessary, dissipated as heat in a regenerative resistor to decelerate the system.

– In SEW‑EURODRIVE’s calculation procedure, the mechanical energy absorbed by the brake and the electrical energy that must be processed by the inverter are treated as separate verification items. See SEW‑EURODRIVE DRN.. calculation process.

– The basic role and selection concept of regenerative resistors themselves, although described for servo applications, are the same as in our article “Selection of Servo Regenerative Resistors”: the focus is on “energy handling”, and the role is different from “mechanical holding”.

1. Independent safety brake / catch mechanism

– These are safety mechanisms independent of the motor, installed when a risk assessment concludes that additional protective measures are necessary, for example in elevators or high‑level material handling.

– Lock pins, ratchets, and anti‑drop safety brakes fall in this category; their design philosophy and evaluation criteria are different from those of motor brakes.

– Rockwell Automation emphasizes, for vertical axes with holding brakes, the importance of understanding behavior on loss of power and of performing a proper risk assessment; this is mainly a safety‑oriented discussion. See Rockwell Automation – Vertical Load and Holding Brake Management.

In RFPs and specifications, organizing requirements along the following lines helps smooth communication with suppliers:

• “Role of the motor‑integrated brake”: holding at standstill / holding under power failure / assisting emergency stops, etc.
• “Role of inverter‑based deceleration control”: deceleration time for normal stops / overload protection / handling of regenerative energy, etc.
• “Need for independent safety mechanisms”: requirements based on applicable regulations, internal company standards, and risk assessment results.

On this basis, the first step in selecting industrial brake motors for plants in Thailand is to decide clearly at the outset whether your main expectation from the motor brake is “holding only” or “including deceleration and stopping”.

2 Capture application data in the field: axis, load, and stopping scenarios

The next step is to “capture actual field data accurately”.

In SEW‑EURODRIVE’s geared motor design process, it is repeatedly emphasized that motion data (load, speed, operating cycle) are the starting point of all calculations. See SEW‑EURODRIVE DRN.. calculation process.

Below is a checklist of the minimum items you should capture in the field so they can be reflected in the RFP for selection and quotation.

2-1 Which axis, and what is it supporting?

Even when using the same motor brake, the requirements change significantly depending on where it is installed.

• Orientation of the driven axis: horizontal / inclined / vertical
• Directly coupled motor or motor with gear reducer (number of gear stages, approximate ratio)
• Whether the brake is mounted on the motor shaft, on the gearbox secondary shaft, or on an intermediate shaft
• Type of load: tension, pushing, hoisting, rotary table, etc.
• Whether the process involves large load fluctuations (for example, sudden changes at infeed/outfeed)
• At which position you want the load to be supported when the line stops (near the floor / mid‑position / upper limit, etc.)

For vertical and inclined axes in particular, the DRN.. geared motor calculation procedure clearly states that “brake selection is mandatory for hoist applications”, and warns against assuming that “it will probably stop by inertia” in the same way as horizontal conveying. See SEW‑EURODRIVE DRN.. calculation process.

2-2 How to estimate load and inertia

In the RFP you can ask the supplier to “calculate the required torque”, but the load information that forms the basis for that calculation must be defined on the user side.

• Actual load (kg or N)

– Maximum workpiece mass on the conveyor

– Total mass of product, jig, chain, wire rope, pallet, etc. to be hoisted

• Additional safety‑related masses (hooks, ropes, hangers, etc.)
• Moment of inertia of rotating bodies (as far as known)

– For example: drum diameter, roller diameter, length, material, etc.

• For vertical axes with a counterweight: the counterweight mass and mechanical efficiency

In SEW‑EURODRIVE’s brake calculation documentation, static load torque (holding torque against gravity and disturbances) and dynamic load torque (inertial torque from acceleration and deceleration) are treated separately. See SEW‑EURODRIVE BE brake calculation formulas.

Accordingly, if you also separate “static load” and “assumptions during acceleration/deceleration” in the RFP, the supplier’s calculations will be clearer.

2-3 Write out multiple stopping scenarios

Be careful not to treat “normal stops” and “abnormal or fault stops” as if they occur under the same conditions.

In Rockwell Automation’s explanation of vertical axis brakes, it is pointed out that the behavior and risks differ greatly between a controlled stop using the inverter and a stop on total power loss (where the brake closes because its power is removed). See Rockwell Automation – Vertical Load and Holding Brake Management.

Examples of stopping scenarios you should describe in the RFP:

• Normal stop

– Inverter deceleration → nearly zero speed → brake closes → motor de‑energized

– Target stopping time (for example, 2–3 seconds; the value is a user requirement)

• Emergency or protective stop (inverter remains powered)

– Emergency stop button → rapid deceleration by inverter → brake closes

– Required stopping distance, if you have a defined limit

• On power failure

– Main power loss → brake power also lost → spring force closes the brake

– In this case, inverter‑based deceleration control generally does not function, and “how much micro‑movement you can accept” becomes part of the mechanical risk assessment

• Maintenance mode

– Whether a manual handle or manual brake release mechanism is used

– Under which conditions the motor brake should be allowed to open, or must be prevented from opening

The Siemens SINAMICS G120C operating instructions explain that, when using a motor brake on a vertical axis, the inverter should first energize the motor to produce zero‑speed torque, then release the brake before acceleration, and conversely, on stopping, close the brake first and then remove motor torque—i.e. a required “sequence control”. See Siemens SINAMICS G120C Operating Instructions.

If you include such control sequence assumptions—described in words and with a timing chart—as part of the RFP, you can greatly reduce misinterpretation of the specification.

2-4 Field data checklist to incorporate into the RFP

• [ ] Orientation of the target axis (horizontal / inclined / vertical) with drawings
• [ ] Motor position and drivetrain configuration (direct‑coupled / with gearbox / with chain or belt stages)
• [ ] Maximum load (kg or N) and breakdown of its components
• [ ] Information related to inertia (drum diameter, roller diameter, material, approximate inertia)
• [ ] Deceleration time and allowable stopping distance for normal stops
• [ ] Acceptable behavior during emergency stop and power failure (describe an allowable range, not “no movement at all”)
• [ ] Brake opening/closing frequency (per hour / per day)
• [ ] Ambient conditions (temperature, humidity, dust, oil mist, outdoor/indoor)
• [ ] Presence of safety mechanisms (independent brake, mechanical stopper) and allocation of design responsibility

Once these points are clarified, you can move on to the following sections—“conversion of holding torque”, “power supply and failure modes”, and “dynamic braking work”—and conduct much more concrete specification negotiations for brake motors.

3 Converting brake holding torque to motor‑shaft torque

After organizing the field specifications, the next question is: “How do we interpret the brake’s holding torque on the motor shaft side?”

In many catalogs, brake torque is specified as torque at the motor shaft, while in practice the object being held is usually on the gearbox secondary side, drum, or sprocket.

SEW‑EURODRIVE’s brake calculation documents are also based on converting static load torque to the motor shaft side. See SEW‑EURODRIVE BE brake calculation formulas.

3-1 Why convert everything to “motor‑shaft torque”?

• The motor brake is normally mounted at the motor shaft end.
• Through the gearbox ratio and efficiency, the torque on the secondary side and the torque on the primary (motor) side are related.
• Catalog brake torque values are usually defined as motor‑shaft torque, so the “required holding torque” from the application must be matched to that value.

In other words, the practical sequence of thinking is:

1. Calculate the required torque on the “drum/roller/sprocket side” based on the load you want to support.
2. Convert this to the “required torque on the motor shaft” using the reduction ratio and efficiency.
3. Based on that value, compare with the cataloged rated static torque of the brake and obtain calculation support from the manufacturer.

3-2 Simple numerical example (the calculation is only for illustration)

The following is only one example to illustrate the concept. In real projects, you must always refer to the documentation of the specific manufacturer and model you plan to use, and have the calculations checked by their application engineers.

• Load: 60 kg hoisted vertically
• Effective drum radius: 0.1 m
• Gear ratio: 20 (one motor revolution corresponds to 1/20 revolution of the drum)
• For this rough example, gearbox losses are ignored and backdrive efficiency is not quantified

1. Static torque required at the drum (to support gravity)

– Gravitational force: 60 kg × 9.81 m/s² ≈ 588.6 N

– Torque: 588.6 N × 0.1 m ≈ 58.86 Nm

1. Ideal conversion to the motor shaft via gear ratio 20 (ignoring losses)

– 58.86 Nm ÷ 20 = 2.943 Nm

This 2.943 Nm is only an ideal value ignoring losses. It is not the final required holding torque or a design safety margin for the selected product. The final selection value must be determined using product‑specific design data and risk assessment, after confirming with the manufacturer the effects of gearbox losses under back‑driving, load direction, wear, shock, and worst‑case conditions. Note that this example considers static load only and does not cover dynamic stopping.

More important than the numerical result itself is the procedure:

• First calculate the value on the load side, then convert it to “motor‑shaft torque” before comparing with brake torque.
• Recognize that gearbox efficiency and self‑locking characteristics (e.g. worm gears) can be direction‑dependent and must not be treated uniformly based only on catalog efficiency.

3-3 Conversion assumptions that should be stated in the RFP/specification

To align the supplier’s calculations with the user’s assumptions, it is useful to describe the following information in the RFP:

• [ ] How you calculated the required holding torque on the load side (mass, radius, gravitational acceleration, etc.)
• [ ] Planned drivetrain configuration (approximate ratio, worm gear vs spur gear, etc.)
• [ ] Treatment of gearbox efficiency (if you have assumed a value, state the value and the basis)
• [ ] For vertical axes, the load direction and any concerns about backdrive behavior
• [ ] “Minimum required static holding torque” stated not only as a formula but with explanatory text

SEW‑EURODRIVE’s brake calculation documentation shows that multiple parameters must be considered together—static load torque, brake torque, rotational speed and speed difference, work during emergency stops, etc.—and that the process cannot be completed with a single formula. See SEW‑EURODRIVE BE brake calculation formulas.

4 Power supply and failure modes to check for holding under power failure

A point that is often overlooked when discussing brake motors is: “From where is the brake’s power and control circuit supplied?”

Rockwell Automation’s documentation on vertical axis brake management notes that:

• During a normal controlled stop, the drive manages deceleration; but
• On total power loss, the power‑off brake attempts to hold the load, while you cannot rely on the drive to perform deceleration.

See Rockwell Automation – Vertical Load and Holding Brake Management.

In addition, the Siemens SINAMICS G120C manual explains that, when the drive controls the brake coil through a digital output, an interface relay may be needed if the contact capacity is insufficient, and that brake release/closing delays must be considered in drive parameter settings. See Siemens SINAMICS G120C Operating Instructions.

4-1 Identify patterns of brake power supply

Before preparing the RFP, the plant and design teams should identify the following “brake power scenarios”:

1. Normal operation

– From where is the power for the brake coil supplied?

– A dedicated 24 V output from the inverter’s brake supply?

– A separate control power supply (24 VDC, 230 VAC, etc.)?

– Is the brake ON/OFF command directly from the inverter’s digital output, or via a PLC?

1. Inverter fault

– If only the inverter trips, what is the state of the brake?

– Is the brake designed so the coil de‑energizes and the spring closes the brake?

– Does loss of the inverter’s internal power also remove brake control?

1. Control power loss

– If the 24 VDC control power fails, does the brake close rapidly?

– Is the control power maintained for a certain time even if the main three‑phase power fails (presence of UPS, etc.)?

1. Main power loss

– What happens to the brake coil power supply when the whole plant loses power?

– How is the load expected to behave at that moment (hold / small movement / transfer to a safety mechanism)?

In the Oriental Motor BLE2 Series manual, it is explained that the torque generated by the driver (electrical position holding) disappears when the driver power is lost, while a separately specified electromagnetic brake can hold the load even after the main power is turned off. See Oriental Motor BLE2 Series Manual.

This shows that “holding by the drive” and “holding by the motor brake” have different dependencies on the power supply and must not be confused.

4-2 Define expected behavior for each failure mode

If you organize in writing “how you expect the brake to behave under each failure mode” and include that in the RFP, supplier proposals will be more concrete.

For example, for a vertical conveying axis, you might check:

• [ ] Minor inverter faults (such as overcurrent)

– Does the drive attempt a controlled deceleration stop, or does it immediately remove torque?

– Does the brake “close in a controlled manner” on a command from the drive?

• [ ] Severe inverter faults / loss of internal power

– Can the drive maintain its brake control output, or does it drop immediately?

– In that case, does the brake “close by spring force”, or does it remain open?

• [ ] Loss of 24 VDC control power in the panel

– Is the brake circuit dependent on 24 VDC, or on a separate source?

– How does it interface with safety relays and interlocks?

• [ ] Plant‑wide power outage

– Is it assumed that the brake closes by spring force (spring‑applied type)?

– Is there any realistic chance that the drive can “attempt deceleration” using residual DC‑link energy (this is highly device‑specific)?

Rockwell Automation notes for vertical axes that design should not assume successful drive‑based deceleration on total power loss, and that the relationship between brake response time and load energy must be assessed in a risk assessment. See Rockwell Automation – Vertical Load and Holding Brake Management.

4-3 Brake control circuits and protective devices

A brake coil is an inductive load that requires a certain current and is frequently switched.

The Siemens SINAMICS G120C manual recommends using an interface relay when the drive’s digital output does not have sufficient current capacity to drive the brake coil directly. See Siemens SINAMICS G120C Operating Instructions.

For the motor main circuit, separate selection of motor‑protective circuit breakers (MPCB) or molded‑case circuit breakers (MCCB) is required in line with the Thai plant’s power distribution and protection philosophy. Our article “Selecting Circuit Breakers for Motor Protection” deals with thermal and short‑circuit protection on the main circuit side, which is an issue independent from the brake holding function.

In the RFP, you should describe the following items so suppliers can address them:

• [ ] Rated voltage and current of the brake coil
• [ ] Whether the brake is controlled directly from inverter outputs or via external relays
• [ ] Brake release and closing response times (electrical plus mechanical)
• [ ] Required surge suppression in the brake circuit (suppressors, diodes, RC networks, etc.)
• [ ] Interlocking method with main‑circuit protective devices (MCCB, MPCB) including safety circuits

The Lenze/INTORQ BFK468 manual also points out that power quality, environmental conditions, and excessive switching frequency can lead to wear and performance degradation of the brake. See Lenze/INTORQ BFK468 Operating Instructions.

5 Calculate dynamic braking work and stopping distance separately

So far we have focused mainly on “holding (static behavior)”. In real production lines, however, “how far the moving system travels before it stops” is also a key design issue.

In SEW‑EURODRIVE’s brake calculation documentation, apart from static load torque, it is required to calculate and verify separately:

• The dynamic braking work (energy) that must be absorbed by the brake
• The allowable stopping distance
• The loads applied to the gear unit during emergency stops

See SEW‑EURODRIVE BE brake calculation formulas.

5-1 Why “holding torque only” is not enough

With the same brake torque:

• If you rely on the brake alone to perform an “emergency stop from speed” on a high‑inertia, high‑speed line, and
• If you use the brake only for “final stop and holding” after the inverter has already decelerated nearly to zero speed,

the energy absorbed by the brake and the resulting wear are completely different.

The Lenze/INTORQ spring‑applied brake manual explains that:

• Static torque is intended for holding when there is no relative rotation, and
• In an emergency stop while rotating, the brake disc absorbs friction work, leading to heat generation and wear.

See Lenze/INTORQ BFK468 Operating Instructions.

Therefore, your RFP should clearly state:

• Whether you expect the brake to perform “dynamic stopping”, or
• Whether you only want the brake to handle “final stop and holding”.

If necessary, specify an operating concept such as:

• Inverter decelerates → brake engages at low speed; or
• Only in emergency stop situations, allow the brake to perform dynamic stops, within a limited number of occurrences.

5-2 Clarifying the concept of dynamic braking work

In broad terms, dynamic braking work is:

“How much of the rotational kinetic energy plus change in potential energy is handled by the brake?”

SEW‑EURODRIVE’s documentation provides examples in which:

• Kinetic energy is calculated from rotational inertia and speed,
• For vertical loads, the change in potential energy during stopping is added, and
• The sum is compared with the permissible work of the brake.

See SEW‑EURODRIVE BE brake calculation formulas.

You do not have to perform every detailed calculation at the RFP stage, but if you at least attach the following information, suppliers can evaluate the application more smoothly:

• [ ] Maximum operating speed in normal operation (rpm or m/min, etc.)
• [ ] Approximate inertia of rotating parts (or sufficient construction details to estimate it)
• [ ] Expected emergency stop scenario (number per day, or “none as a rule”, etc.)
• [ ] Allowable stopping distance (based on safety fencing, separation distance from operators, and risk assessment results)

5-3 Role sharing between inverter deceleration and regenerative resistor

For inverter‑driven systems, the typical concept is to “first handle dynamic energy electrically, then use the brake for final stop”.

In SEW‑EURODRIVE’s geared motor calculation procedure, items such as:

• Drive current,
• Regenerative energy returned to the DC link, and
• The regenerative resistor that must handle that energy

are treated as confirmation items separate from brake calculations. See SEW‑EURODRIVE DRN.. calculation process.

As described in our article “Selection of Servo Regenerative Resistors”, the design of regenerative resistors focuses on disposing of kinetic energy electrically, and they do not provide any function for “static holding of the load”.

In your RFP, you should therefore indicate a role sharing such as:

• “Dynamic energy is mainly handled by the inverter plus regenerative resistor”, and
• “The motor brake is responsible for final stopping at low speed and for holding at standstill”.

Clarifying this division of roles helps avoid imposing excessive dynamic stopping duty on the brake, which in turn benefits brake life and maintenance requirements.

6 Verify compatibility between brake motor and inverter

Finally, we organize the topic of “compatibility between brake motor and inverter (drive)”.

Here we clearly distinguish between the brake motor itself, the drive control and regenerative resistor, and any independent safety mechanism.

6-1 Interface between inverter and brake control

The Siemens SINAMICS G120C operating instructions describe a brake control function for vertical axes with the following sequence:

• Motor excitation → brake release → acceleration
• Deceleration → brake closing → motor torque OFF

They also recommend using an interface relay if the digital output used for brake control does not have sufficient capacity. See Siemens SINAMICS G120C Operating Instructions.

Key points you should confirm or specify in the RFP/specification:

• [ ] Planned inverter model and whether it has built‑in brake control functions and terminals
• [ ] Compatibility between brake coil voltage/current and inverter output capacity
• [ ] Brake release and closing delays (and whether they can be compensated via parameters)
• [ ] Brake control sequence (timing) and its consistency with the safety circuit

6-2 Short‑cycle operation and brake switching frequency

In high‑frequency positioning or index conveyor applications, brake opening/closing counts become high, and brake response time can influence cycle time.

SEW‑EURODRIVE’s holding brake documentation lists as important parameters for short‑cycle operation:

• No‑load switching frequency,
• Mechanical response time,
• Controller delay, and
• Minimum rest time.

See SEW‑EURODRIVE Holding Brake – No‑load Switching Frequency.

The Lenze/INTORQ BFK468 manual also warns that excessive switching frequency and high ambient temperature accelerate wear. See Lenze/INTORQ BFK468 Operating Instructions.

Information you should provide in the RFP:

• [ ] Approximate brake opening/closing operations per hour
• [ ] Expected duty cycle (energization ratio) of the brake
• [ ] Required cycle time and extent to which brake response time can affect it
• [ ] Ambient temperature and cooling conditions (inside sealed enclosure / with or without fan, etc.)

In response, you can request from suppliers:

• The permissible no‑load switching frequency of the brake
• Recommended minimum rest time
• Any recommended brake size or options (temperature sensor, wear monitoring, etc.) as needed

6-3 Role sharing among brake motor, regenerative resistor, and safety brake

Finally, let us again clearly distinguish the roles of the three main elements:

1. Motor‑integrated brake (brake motor)

– Main roles: holding the load at standstill, automatic holding on power failure, and assisting final stopping at low speed

– Items to evaluate: static holding torque, dynamic braking work, switching frequency, response time, and power/control circuits

1. Inverter plus regenerative resistor (electrical braking)

– Main roles: controlled deceleration in normal operation, handling of kinetic energy, and preventing overvoltage during regeneration

– Items to evaluate: motor and load inertia, deceleration time, regenerative energy amount, resistor power rating and permissible duty

– Reference: Our article “Selection of Servo Regenerative Resistors” focuses on the energy‑calculation concept; it is a separate topic from “holding brakes”.

1. Independent safety brake / anti‑drop mechanism

– Main roles: redundant safety mechanisms aimed at personal protection and regulatory compliance

– Items to evaluate: applicable machinery safety standards, required performance level/SIL, fail‑safe design concepts, and periodic inspection methods

– Rockwell Automation’s vertical axis documentation also states that a holding brake alone should not be regarded as a safety brake; instead, system design must be based on risk assessment. See Rockwell Automation – Vertical Load and Holding Brake Management.

In practical projects for plants in Thailand, cost, delivery time, and existing infrastructure constraints make it difficult to optimize all of these at once.

However, by embedding the following perspectives into your RFP and specifications:

• Separating “stopping” from “holding”,
• Organizing field specifications and expressing them as motor‑shaft torque,
• Writing out power supply arrangements and failure modes in concrete terms,
• Sharing dynamic braking work between inverter plus regenerative resistor and the brake, and
• Checking inverter–brake control interfaces and switching‑frequency limits,

you can significantly improve the quality of technical discussions with suppliers and ultimately arrive at more appropriate industrial brake motor selections.

7 Matching opening/closing time, cycle count, and heat

If you size a brake motor only by “torque,” the brake side can easily overheat under actual operating conditions in Thai plants, leading to premature wear or loss of synchronism.

This section organizes how to align specifications with real machine conditions from the viewpoints of brake opening/closing time, cycle count, and heat.

7.1 Opening/closing time: check both motor and control panel

The opening and closing of a brake motor consists of the accumulation of the following time elements:

• Mechanical response time from the moment the brake’s electromagnetic coil is energized until the brake is fully released
• Control delay until the inverter or drive starts to ramp current into the motor
• Time from removal of motor torque at stop until the brake again develops full clamping force

SEW‑EURODRIVE recommends evaluating the combination of “mechanical response time” and “control-side delay” when designing brakes, and for short-cycle applications, it states that the minimum stop interval must be verified based on both factors.3

In practice, you should confirm and define the following in the specification:

• Brake release/engagement times in the vendor’s datasheet and manuals (often in the millisecond range)
• Brake control logic of the planned inverter or servo drive (for example, a sequence such as Siemens SINAMICS G120C, where the rotor is held with zero-speed torque while the brake is released, then accelerated afterward5)
• Response time of PLC/relay outputs and the power interface to the brake coil (direct connection or via interface relay)

For example, if an index table has a cycle time of 2 seconds, and you assume 80 ms for brake release and 50 ms for inverter zero‑speed holding → acceleration, the effective acceleration and deceleration time becomes constrained. When such “time contention” exists, the acceleration/deceleration profile assumed at the design stage may not be achieved, causing increased variation in stopping position accuracy.

7.2 Cycle count and no‑load switching frequency: do not reuse catalog values as‑is

Brakes have limits for “number of switching operations at no load” and “permissible switching frequency.” If you exceed these, overheating and wear accelerate. SEW‑EURODRIVE documentation presents a workflow in which static load torque, brake torque, speed, speed difference, emergency stop work (J), and stopping distance are combined to evaluate brake load.2

SEW also defines the “no‑load switching frequency” of holding brakes and notes that, for short cycles, mechanical response time and minimum stopping intervals must be taken into account.3

In Thai plant procurement specifications, if you at least distinguish the following conditions, vendor comparison becomes much easier:

• Number of opening/closing operations per hour in normal operation (e.g., conveyor start/stop, changeover)
• “Maximum” switching frequency including emergency stops (taking into account expected PLC logic and safety relay actuation)
• Load condition at brake switching (pure static holding only, or combined with deceleration/stopping from high speed)

The way you view margin in allowable cycle count differs completely depending on whether the brake is used purely for “holding” or whether you also rely on it, together with drive control, for deceleration and stopping.

Rockwell Automation likewise recommends, for vertical axes, a configuration in which the drive performs deceleration control and the brake is used only for final holding, and warns that letting the brake absorb all the energy rapidly increases wear.6

7.3 Thermal aspects: brake work and heat dissipation paths

In applications where the “work (energy)” applied to the brake is large, you cannot ignore thermal design.

SEW‑EURODRIVE’s guidelines for brake calculation organize thermal load from the following viewpoints:12

• Energy (J) absorbed by the brake in a single stop
• Total work over a given time period (e.g., per hour)
• Brake thermal capacity and heat dissipation performance (ambient temperature, mounting orientation, cooling conditions)

For spring‑applied brakes such as Lenze/INTORQ BFK468, the documentation explains that while frictional work is almost zero during static holding, emergency stops from rotation generate large frictional work and wear.4

In other words, required thermal margin depends on whether the brake is used “for holding only” or also “for frequent braking.”

If measured ambient temperature at the installation site reaches 35 °C, state that condition explicitly in the design basis. When ambient temperature is high, margin to the brake’s permissible temperature rise is reduced, so it is effective to explicitly state the following in the RFP and compare each vendor’s responses:

• Expected ambient temperature range (for example, normal operation 0–40 °C, temporary peaks 45 °C, adjusted to reality)
• Actual temperature at control panel and machine (whether the motor area is a continuously hot line, or inside an air‑conditioned area)
• Vendor‑stated temperature rise and any derating applied versus brake work and switching frequency

Furthermore, as brake temperature rises, spring force, friction coefficient, and coil resistance can change, potentially affecting holding torque and response time. You can check margin for continuous high‑temperature operation by asking vendors about the “range of guaranteed holding torque at the expected ambient temperature.”

8 Include Thai plant environment, maintenance, and spare parts in the specification

8.1 Organize Thailand‑specific environmental conditions

In Thai factories, the following environmental factors significantly affect brake motor service life and reliability:

• High temperature and high humidity (risk of condensation)
• Dust (bulk handling in food, feed, cement, wood, recycling, etc.)
• Corrosive gases and mist (chemicals, washing processes, coastal sites)
• Frequent cleaning (high‑pressure washing, chemical washing)

The Lenze/INTORQ BFK468 operating instructions also warn that environmental conditions (humidity, dust, corrosive atmosphere) can cause ingress into the brake interior and degradation of friction surfaces, and they emphasize the need to select appropriate protection ratings and covers.4

In the RFP or specification, it is advisable to describe “environmental conditions” concretely as below and require each vendor to respond on suitability and options:

• Ambient humidity and presence/absence of condensation (e.g., humidity above 90 %, condensation present/absent)
• Type and level of dust (visibly airborne, light deposition, almost none, etc.)
• Cleaning frequency and method (high‑pressure water, steam, solvent, weak alkaline detergent, etc.)
• Distance from the sea and presence of salt exposure (salt mist, outdoor installation, etc.)

Typical response options on the brake motor side include:

• Specifying an IP protection rating (without hard‑coding legal values or ratings; compare vendor proposals based on application and environment)
• Options such as anti‑corrosion coating, stainless shaft, reinforced seals
• Dust covers to reduce ingress into the brake interior
• High‑humidity‑tolerant insulation grades and impregnated coil specifications

8.2 Maintainability: inspection access and adjustment mechanisms

No matter how high‑performance the brake may be, if maintenance is difficult, local mechanics in Thailand may not be able to adjust it, and it ends up being “left until it fails.”

For SEW‑EURODRIVE and Lenze/INTORQ brakes, procedures for air gap adjustment, wear limit checks, and replacement are described specifically in the manuals,24 and whether the brake structure allows easy access to follow these procedures is a practical key point.

Checkpoints that should be included in the procurement specification:

• Whether brake inspection and adjustment are possible without removing the motor from the line
• Presence of holes/scales/gauges for air gap measurement
• Availability of visual wear limit indicators and wear‑detection switch outputs
• Method for replacing the brake coil (unit replacement without rewinding, etc.)
• Recommended maintenance intervals and required skill level (general mechanic sufficient, or specialist required)

For example, BFK468 offers optional microswitches for monitoring air gap or wear,4 and effective use of these can help Thai plants avoid situations where “the brake is used right up to its limit and then suddenly stops working.”

8.3 Spare parts supply chain: Thai stock and compatibility

Considering life‑cycle cost of a brake motor, whether spare parts can be secured within Thailand is extremely important.

SEW‑EURODRIVE and other major manufacturers supply standard brake units, spring sets, friction linings, and similar items as separate parts, but delivery time and procurement routes differ greatly depending on country and distributor.

At RFP stage, request vendors to clarify and document:

• Whether there is stock of brake motor bodies and replacement kits in Thailand, or everything is imported
• Expected lead time (difference between standard stock items and non‑stock/make‑to‑order items)
• Possibility of model unification (whether brake types can be standardized as far as possible across the line)
• Policies on compatibility with successor models in terms of coil voltage, brake size, and so on

You also need to consider component procurement on the drive side (inverters, panel components, motor‑protection devices, etc.). For motor protection, it is good practice to align with your internal materials or columns on “motor protection circuit breaker (MPCB) selection,” such as:

https://tomastc.com/en/blog/motor-protection-circuit-breaker-selection-thailand-2026-en/

9 Specification table and vendor questions to include in the RFP

This section organizes specification items intended for actual procurement RFPs.

The table below is only an “example of questions and entry fields”; you must define the actual values and conditions on the project side.

9.1 Brake motor specification table (sample RFP)

Treatment of “safety” is particularly important here.

Rockwell Automation points out that, in vertical‑axis applications, even if a spring‑applied brake is triggered on power loss, the amount of axis movement until the brake fully clamps depends on energy, friction, and response time; therefore, you must not simply judge “spring‑applied = safe.”6

At RFP stage, it is realistic to clearly state that “this brake alone does not guarantee the machine’s overall safety category or PL,” and to assume that final decisions will be made based on separate risk assessment and safety circuit design.

9.2 Technical questions for vendors

In addition to the main RFP, preparing a separate technical question sheet for vendor responses makes comparison easier. Examples include:

• Which brake motor series does your company recommend for vertical load applications?
• Can you provide documentation showing the relationship between brake work (J) per stop and allowable work per hour for the assumed load, speed, and deceleration time (e.g., SEW‑EURODRIVE‑style calculation sheets12)?
• What margin exists between catalog no‑load switching frequency and our assumed (normal/maximum) cycle counts?
• Including supply‑disruption risks, what is your spare‑parts supply structure within Thailand?
• What is your recommended configuration for surge protection and noise suppression for the brake coil (interface relays and suppressors)?
• Regarding power‑failure holding of vertical axes, can you provide the recommended control sequence and precautions from your manual (and alignment with Rockwell6 and Siemens5 concepts)?

By asking questions grounded in publicly available technical documents and manuals, you can clearly see the difference between manufacturers who provide full calculation bases and those who only provide catalog values.

10 How to verify holding, stopping, and power failure in FAT and SAT

Fundamental performance of brake motors must be verified during Factory Acceptance Test (FAT) and Site Acceptance Test (SAT). This section presents test conditions that should be defined for a project and examples of typical test matrices.

10.1 Fundamental precondition: secure and isolate hazardous loads

The top priority is to “prevent dangerous dropping or ejection during testing.”

Rockwell Automation recommends that, when testing and adjusting vertical axes, loads be mechanically supported or restrained to prevent hazards from falling,6 and this concept is equally applicable in Thai plants.

Specifically, the following measures should be stated in the specification as “mandatory preconditions” for tests:

• Support vertical loads with test dummy weights and/or drop‑prevention stoppers, providing redundancy
• Define a safety zone for testing, with clearly marked restricted areas and emergency stop switches
• Apply lockout/tagout (LOTO) principles to the test motor power supply, including physical isolation and clear identification
• Follow the test and adjustment procedures in the manufacturer’s operating instructions, and do not perform operations that deviate from them4

All stakeholders must also understand in advance that there is a delay between power interruption and the brake developing full clamping force, and that some movement due to inertia may occur during this interval.6

10.2 FAT: system‑level tests witnessed at the manufacturer

In FAT, you verify operation at “line level,” including not only the brake motor but also inverters, control panels, and safety circuits.

Below is an example FAT test matrix (values are to be defined by each project):

It is important that criteria such as “stopping distance,” “allowable position deviation,” and “temperature‑rise limit” be agreed for each project in advance. As SEW‑EURODRIVE notes, allowable stopping distance and gear‑unit load depend on several calculated values such as deceleration time, inertia, and brake work.1

FAT may not always reproduce the full behavior during complete power outage, which can be hazardous, but you should at least include and evaluate:

• When the inverter trips, at what timing the brake operates and how far the axis can move
• At inverter restart, whether the brake release sequence and zero‑speed holding control are correctly coordinated5

10.3 SAT: on‑site verification with actual loads and power conditions

In SAT, you perform final verification of brake motors under actual loads, line configuration, and power conditions.

As with FAT, you prepare a test matrix, adding SAT‑specific items such as:

In power‑failure simulation tests, as Rockwell points out,6 when supply is lost completely, the drive’s deceleration control is ineffective, and the load may move a certain distance under inertia before the brake clamps. Whether this “movement distance” is acceptable in terms of safety depends on the machine’s stops, latches, and guides, and must be judged in the context of overall risk assessment.

Include the following notes in the SAT plan:

• The brake is a “holding device that develops clamping force on power loss,” and does not necessarily satisfy all machine safety standard requirements by itself.
• Where necessary to prevent falling of hazardous loads, additional safety brakes, mechanical ratchets, or stops should be used.
• During tests, do not perform operations prohibited by the manufacturer’s operating instructions (such as starting while manually releasing the brake).4

11 Common selection mistakes and decision branches

This section summarizes common selection mistakes in Thai plants and decision points to avoid them.

11.1 Assuming “larger motor = sufficient brake margin”

Sometimes it is assumed that if the motor is oversized, the brake holding force will automatically be sufficient as well. However, as SEW‑EURODRIVE’s calculation flow shows,12 you must evaluate static load torque, gear ratio, motor‑shaft‑equivalent torque, and brake specifications separately.

Decision branches:

• Is the load strictly vertical, an inclined conveyor, or horizontal only?
• How much static holding torque is required versus rated operating torque?
• Does brake torque exceed the permissible torque of gears or coupling components (risk of mechanical damage from excessive braking)?

11.2 Misinterpreting “spring‑applied = safety brake”

Spring‑applied brakes (which clamp when power is removed) are widely used as “fail‑safe” holding devices. However, they do not automatically satisfy safety categories or performance levels.

• Lenze/INTORQ BFK468 manuals show that static holding and dynamic emergency braking generate very different frictional work and temperature rise, leading to application‑specific limits.4
• Rockwell recommends assessing vertical axes via risk assessment as a system combining drive, brake, and safety circuits.6

Decision branches:

• Adjust the level of safety measures depending on whether people are directly exposed in the hazard area or the line is unmanned material handling
• Decide whether to dedicate the brake to “holding only” and assign emergency stopping to drive control plus an independent mechanical locking mechanism
• Consider introducing safety functions such as Safe Torque Off (STO) or dual‑channel stop monitoring

11.3 Confusing inverter braking with mechanical brakes

Inverters and servo drives provide electrical deceleration using regenerative resistors. This is only for “slowing rotation” and is different in role from mechanical brakes that “hold the load when power is lost.”15

Documentation for Oriental Motor’s BLE2 Series also states clearly that driver‑generated holding torque disappears when power is lost, and that a mechanical electromagnetic brake takes over holding the load.7

Decision branches:

• Always provide a mechanical brake on motors for vertical axes or hazardous loads
• Understand that regenerative resistors are for processing braking energy only, and must not be expected to provide holding (for servo regenerative resistor sizing, see your internal resources or columns such as:

https://tomastc.com/en/blog/servo-regenerative-resistor-selection-thailand-2026-en/)

• Configure drive stop sequences (brake release/engagement timing) according to the product manual5

11.4 Overlooking cycle count and thermal load

In conveyors and index drives, cycle counts are high and the brake opens and closes frequently.

SEW‑EURODRIVE recommends brake design that combines no‑load switching frequency, speed difference, and stop work,23 so judging “holding torque is sufficient, so OK” is not enough.

Decision branches:

• Will the brake open/close every cycle, or will it hardly operate during long periods of continuous running?
• For emergency stops, will you concentrate load on the brake, or decelerate via the drive and then hold?
• In high‑temperature areas, is derating necessary in relation to cycle count?

11.5 Postponing spare parts and maintenance arrangements

If you focus only on initial unit price and adopt products without confirming Thai spare‑parts and service capabilities, a failure can lead to extended line downtime.

Including questions on supply structure and maintainability in the RFP, as outlined above, can greatly reduce this risk.

12 FAQ: practical questions on brake motor selection

This section organizes five common practical questions from engineers and buyers at Thai plants.

12.1 Q1: What should we check to prevent loads from falling during power failure?

A: Start with risk assessment of the entire machine. Then check the following in order:

1. Whether the motor is equipped with a mechanical holding brake (SEW‑EURODRIVE also recommends using brakes on vertical axes1).
2. Whether the brake’s static holding torque, after conversion via gear ratio, has sufficient margin against the load‑side torque.
3. Estimate, referencing Rockwell’s approach,6 how far the load can move under inertia when the drive cannot perform deceleration control during complete power loss.
4. If falling cannot be tolerated, consider adding safety mechanisms such as mechanical latches, safety brakes, or dual supports.
5. In FAT/SAT, conduct power‑failure simulation or equivalent tests and confirm behavior on the real equipment.

The key point is to avoid making absolute statements like “once a brake is installed, loads will never fall.” Holding performance can degrade due to wear, misadjustment, or unexpected thermal conditions, so you must combine redundancy and periodic inspection.

12.2 Q2: How do we determine the required holding torque?

A: Holding torque must be determined by converting load, gear ratio, friction, and related conditions to the motor shaft. SEW‑EURODRIVE design documents present procedures that organize static and dynamic torque and brake torque, and evaluate load on gear units and brakes separately.12

In practice, proceed as follows:

1. Calculate load‑side torque (e.g., T_load) using load weight, sprocket or drum diameter, lifter structure, etc.
2. Convert to motor‑shaft torque using gear ratio and efficiency.
3. Define target holding torque T_hold_req by applying an internal safety factor as needed (the factor itself should be set by internal standards and risk assessment).
4. Check that catalog “rated brake torque” meets or exceeds T_hold_req.
5. Also verify that gear‑unit allowable torque is not exceeded.

Factors and limits used here are not universal constants. Designers and safety personnel must agree on them after considering load type, human proximity, allowable stopping position error, and similar aspects.

12.3 Q3: Are there any special brake considerations when using inverters?

A: In inverter‑driven systems, you can flexibly set start/stop profiles and zero‑speed holding functions, but if brake control is not correctly coordinated with them, unexpected motions and accelerated brake wear can occur.

• On Siemens SINAMICS G120C, for example, there is a sequence in which the motor is magnetized and produces zero‑speed torque before brake release, then transitions to acceleration,5 which is effective for smooth starts on vertical axes.
• On stopping, the recommended structure is for the drive to decelerate first, then for the brake to engage near standstill, and only then for motor torque to be reduced to zero.56

Points to check for inverter compatibility:

• Whether the drive has a “digital output for brake control” and whether its rating matches the brake coil or relay ratings5
• Presence and range of parameters for adjusting brake release/engagement timing
• Whether the regenerative resistor and braking chopper can handle the expected energy during emergency stops (holding must still be done by the mechanical brake)1

Because these aspects are product‑specific, always refer to the intended drive’s manual and confirm recommended wiring and parameter settings for brake control.

12.4 Q4: How can we reduce brake wear in frequent stop/positioning applications?

A: In high‑cycle applications, the key is how you divide responsibilities between drive control and the brake.

• SEW‑EURODRIVE brake design guidelines recommend evaluating brake load by combining stop work, switching frequency, and speed difference.2
• Lenze/INTORQ BFK468 manuals explain that wear differs greatly between static holding and dynamic braking of a rotating shaft.4

Practical approaches to reduce wear:

1. Assign normal stopping and positioning to inverter/servo speed and position control, and use the brake only for final holding.
2. Reduce emergency stop frequency by improving normal stop logic and operating rules.
3. Compare catalog no‑load switching frequency with actual cycle counts and select brake size/grade so that sufficient margin exists.3
4. Utilize wear‑monitoring switches and air gap adjustment mechanisms, and perform preventive‑maintenance‑based adjustment and replacement.

12.5 Q5: How should we position brake motors in equipment with strict safety requirements?

A: In equipment with high safety requirements (vertical lifts with human access, lifting stages, hazardous materials handling, etc.), brake motors must be treated as “one element in the safety architecture.”

• Rockwell recommends combining multiple layers such as Safe Torque Off (STO), position monitoring, and dual brakes for vertical axis safety.6
• For Oriental Motor’s BLE2 Series, for example, load holding is provided by the mechanical brake in combination with drive torque, but the documentation is explicit that, when power is lost, driver torque disappears and only the mechanical brake remains to hold the load.7

Key points for high‑safety equipment:

1. Perform risk assessment of the entire machine and define which protection layers will handle which failure modes.
2. Expect “holding function” from the brake motor alone; make final decisions on safety category and PL based on the combination of safety control circuits, mechanical design, and safety PLCs.
3. Even if the brake is safety‑certified, improper wiring or control logic can still fail to meet safety requirements, so you must refer to the manufacturer’s safety application notes.

13 Summary: decide comparison tables and test conditions as a pair

If you select brake motors solely by comparing catalog values, gaps often arise with actual operating conditions and safety requirements in Thai plants.

The selection process can be summarized as follows:

1. Concretely define application, load, cycle, and environment, and reflect them in the RFP specification table.
2. Using SEW‑EURODRIVE and Lenze/INTORQ materials as reference, establish internal calculation flows that consider static torque, brake work, switching frequency, and thermal load.123
3. Design system‑level behavior including inverter/servo control sequences (brake release/engagement timing, zero‑speed holding).56
4. In the RFP, distribute a vendor question sheet together with the specification table, and explicitly compare calculation bases, maintenance arrangements, and safety stance.
5. In FAT/SAT, define test conditions and acceptance criteria (load, temperature, allowable stopping distance, etc.) and verify holding, stopping, and power‑failure behavior only after mechanically securing hazardous loads.
6. Do not expect “absolute safety” from the brake motor alone; treat it as one element of mechanical, control, and safety systems, and design life‑cycle aspects including periodic inspection and spare‑parts supply chain.

It is essential to determine comparison tables (RFP specifications) and test conditions (FAT/SAT) “as a pair.”

If functions and performance requested in the RFP are not reflected in test items and criteria, disagreements like “this is not what we expected” are likely after commissioning. Conversely, when specifications and tests are consistent, it becomes much easier to establish agreement for stable operation and safety in Thai plants.

In many Thai factories, it is difficult to decide which brake motor type is appropriate and what level of holding torque and cycle count should be assumed without reviewing conditions for each line.

For a specific project, you can share drawings and existing equipment details through our contact form. We can help organize the RFP specifications and draft FAT/SAT test items even before a model is selected.

Sources

• SEW‑EURODRIVE, “DRN.. gearmotors basic calculation process”, edition 02/2026 (calculation flows for static/dynamic torque, stopping distance, brake work, etc.)

https://download.sew-eurodrive.com/download/html/33346739/en-EN/21903384203.html

(Accessed: 2026-10-26)

• SEW‑EURODRIVE, “BE brake calculation formulas”, edition 06/2026 (design guidelines for brake torque, no‑load switching frequency, emergency stop work, etc.)

https://download.sew-eurodrive.com/download/html/31976603/en-EN/1947997658763680744075.html

(Accessed: 2026-10-26)

• SEW‑EURODRIVE, “Holding brake no-load switching frequency”, edition 04/2026 (relationship between no‑load switching frequency, mechanical response time, and control delay)

https://download.sew-eurodrive.com/download/html/31989101/en-EN/59312593547.html

(Accessed: 2026-10-26)

• Lenze/INTORQ, “Operating instructions – Spring-applied brake BFK468”, 01/2024 (structure of spring‑applied brakes, wear, environmental conditions, air gap monitoring, etc.)

https://www.lenze.com/fileadmin/lenze-selection/documents/en/Operating_Mounting_Instructions/operating-instructions-spring-applied-brake-BFK468_EN.pdf

(Accessed: 2026-10-26)

• Siemens, “SINAMICS G120C Operating Instructions”, section 6.11, 11/2016 (brake control sequence, zero‑speed holding, precautions for using interface relays)

https://cache.industry.siemens.com/dl/files/769/109744769/att_912473/v1/G120C_op_instr_1116_en-US.pdf

(Accessed: 2026-10-26)

• Rockwell Automation, “Vertical Load and Holding Brake Management”, 04/2019 (stopping sequences, behavior during power failure, concepts for risk assessment on vertical axes)

https://literature.rockwellautomation.com/idc/groups/literature/documents/at/motion-at003_-en-p.pdf

(Accessed: 2026-10-26)

• Oriental Motor, “BLE2 Series – Operating Manual HP-5105-6E” (role sharing between electromagnetic brake and driver holding torque)

https://www.orientalmotor.com/products/pdfs/opmanuals/HP-5105-6E.pdf

(Accessed: 2026-10-26)