Industrial electromagnetic clutch-brake unit

01

Size torque from load, inertia and stopping time

Warner Electric's sizing guide lists, in order, transmissible torque, energy source, actuation mode, operating environment, heat dissipation and mounting orientation. It distinguishes static torque (at zero relative speed), dynamic torque during acceleration or deceleration, and residual torque in non-energised multi-disc units. Nominal torque is Mn = 9550 · P / n (Nm, kW, min⁻¹); where the real torque is unknown it multiplies this by a safety factor K of 2.5–3 for electric motors, 4–5 for diesel engines and 5–6 for compressors. [1]

For an accurate selection it adds the load torque Ml to the acceleration or deceleration torque Md = J · n / (9.55 · t), where J is the total inertia in kg·m² including reflected inertias and the unit's own parts; the unit's nominal torque must exceed the total. The real time is t = J · n / (9.55 · (Mn ± Ml)), with minus for a clutch and plus for a brake. It permits tooth clutches only for engagement at zero speed difference, applies K = 3 to power-on tooth devices, and forbids them for lifting. [1]

Editorial calculation: assume 2.2 kW is the mechanical shaft power at 1,450 min⁻¹ and apply only Warner’s quick-selection factor for an electric-motor drive. Then 9550 × 2.2/1450 ≈ 14.5 Nm; multiplying by the stated 2.5–3 gives approximately 36–43 Nm. In a separate hypothetical stop, assume constant 40 Nm dynamic brake torque, total reflected inertia 0.05 kg·m² at that shaft, initial speed 1,450 min⁻¹ and constant 2 Nm friction assisting the stop. The catalogue model gives 0.05 × 1450/(9.55 × 42) ≈ 0.18 s. This excludes coil/control delay, torque build-up, speed-dependent friction and elastic motion; it is not a measured machine stopping time or a selected brake rating. [1]

Give the supplier the drive power and speed, load torque, total inertia at the unit's shaft, required start and stop times, cycles per minute, mounting (shaft, flange, motor C-face) and orientation, environment (dry, oil, dust), supply voltage and switching, and whether the brake must hold on power loss.

02

Check heat per cycle, run-in and switching

Warner Electric states that friction turns mechanical energy into heat that the unit must absorb without damage, and gives the energy per engagement as W = (J · n² / 182.5) · (Mn / (Mn ± Ml)) joules, to be checked against each product's heat dissipation diagram; if size by heat differs from size by torque, it advises the larger. Dry units are recommended for −25 to +40 °C; lubricated multi-disc units suit high energy per cycle, with oil below 40 cSt at 50 °C. [1]

It notes that friction torque ratings assume 'run in' conditions: new units may transmit below 50% of nominal torque, reached after a run-in of repeated operations with a differential speed above 1 m/s, so a run-in is recommended for positioning precision and rapid acceleration. Its electric units run on DC or rectified AC at standard 24, 103.5 and 207 V; switching on the AC side is 5 to 6 times slower than on the DC side, some electrically released devices use a bi-voltage supply, such as 103.5/48 or 207/103.5 V DC, with the higher voltage for the initial armature actuation and the lower to retain that armature position; for an electrically released brake, energisation releases the brake rather than applying braking torque, and the back EMF at switch-off should be suppressed. [1]

Editorial heat arithmetic: under the same constant-torque stopping assumptions, with the 2 Nm load friction opposing rotation and assisting deceleration, Warner’s energy expression gives approximately 549 J per brake stop (about 550 J). Assume exactly 10 identical stops each minute, no other clutch/brake heating and stable repeated operation: average brake dissipation is approximately 5.49 kJ/min, or 91 W (about 90 W). Average power alone does not establish the permissible engagement energy, peak temperature or cooling interval; check both per-cycle and duty limits on the selected unit’s curves. The 0.18 s mechanical model is not a press safeguarding input. [1]

03

Compare combined clutch-brake units with spring-applied brakes

Kendrion's INTORQ 14.800 is a ready-to-install clutch-brake combination in a single housing for clocked drives at mains-synchronised motor speed: dry-running, backlash-free, engaged by applied DC voltage, in five sizes with rated torques from 7.5 to 120 Nm, insulation temperature class B (130 °C) and a patented wear-adjustment mechanism for resetting the air gap. [2]

Where the drive must hold or stop when power is lost, Kendrion's spring-applied (fail-safe) brakes cover torque from 0.22 Nm (Servo Line, for servo motors) through 1.5–600 Nm (BFK458, for IEC gear motors) and 4–125 Nm (BFK457, for industrial trucks and AGVs) to 100–2,400 Nm (BFK468, for hoists and demanding emergency stops). [3]

The series torque spans do not select a unit for the preceding drive example. Confirm power-loss action, dynamic versus holding duty, permissible energy, speed, mounting, wear condition and control supply for the specific size. A spring-applied operating principle alone does not establish the safety performance of the complete machine. [2] [3]

04

Check stopping time where the unit drives a power press

For applicable US mechanical power presses, OSHA specifies brake capability and part-revolution clutch/control behaviour. This is a complete-machine requirement; a generic clutch-brake torque rating does not establish press compliance. [4] [5]

OSHA distinguishes presence-sensing/two-hand-control provisions from PSDI operation. The PSDI distance rule includes sensor and intervening-control response, brake-monitor allowance and penetration depth, with specified stopping-time measurements. Do not use the simplified distance expression for a PSDI installation. [5]

Obtain the press integrator’s measured stop-time record, applicable safeguarding calculation and brake-monitor validation for the operating mode. The catalogue’s mechanical deceleration estimate excludes control and actuation delays. [5]

05

Sunrise’s electromagnetic clutch and brake assemblies

Sunrise lists FMP and FMT electromagnetic clutch-brake assemblies alongside separate clutches and brakes. Confirm the actual assembly’s power-on or spring-applied state, allowed duty and supplied controls; the Warner and Kendrion examples are not Sunrise ratings.

06

Field coil, armature, torque interface and control supply

07

Static and dynamic torque, per-cycle heat and electrical response

08

Send the drive, load and cycle data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Drive: [power; speed; motor or engine]
Load: [load torque; inertia at unit shaft]
Motion: [start and stop times; cycles per minute]
Unit: [clutch; brake; combination; power-on or spring-applied]
Mounting: [shaft; flange; orientation; environment]
Electrics: [supply; DC switching; overexcitation]

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