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1. INTRODUCTION
1.4 Electromagnetic brake
CAUTION
The servo motor with an electromagnetic brake can be used to prevent a drop in vertical lift applications or to
ensure double safety at an emergency stop, for example. When performing servo motor operation, supply
power to the electromagnetic brake to release the brake. Switching power off makes the brake effective.
(1) Electromagnetic brake power supply
Prepare the following power supply for use with the electromagnetic brake only. The electromagnetic brake
terminals (B1, B2) have no polarity.
24VDC power
supply for
electromagnetic
brake
The surge absorber (VAR) must be installed across B1-B2. For the selection and selection example of the
surge absorber, refer to "Electromagnetic brake characteristic" in the chapter of each servo motor series.
When you use a diode for a surge absorber, the electromagnetic braking time will be longer.
(2) Sound generation
Though the brake lining may rattle during operation, it poses no functional problem.
If braking sound occurs, it may be improved by setting the machine resonance suppression filter or
adaptive vibration suppression control in the servo amplifier (drive unit) parameters. For details, refer to the
servo amplifier instruction manual.
(3) Selection of surge absorbers for electromagnetic brake circuit
The following shows an example how to select a varistor with a surge absorber.
(a) Selection conditions
Electromagnetic brake
specification
Desired suppression voltage
Durable surge application time
The electromagnetic brake is provided to prevent a drop at a power failure or servo
alarm occurrence during vertical drive or to hold a shaft at a stop. Do not use it for
normal braking (including braking at servo lock).
The electromagnetic brake has a time lag. Use the electromagnetic brake so that
servo motor control starts after the electromagnetic brake has completely opened.
Be sure to check the time lag of the braking with a real machine.
Configure an electromagnetic brake circuit so that it is activated also by an external
EMG stop switch.
For details of the circuit configuration and timing chart, refer to the Servo Amplifier
Instruction Manual.
While the electromagnetic brake is opened, the motor may be raised to high
temperature regardless of driving.
The life will be shorten under sudden acceleration/deceleration conditions.
B1
Switch
Switch
VAR
U
B2
Item
R[
]: Resistance
L[H]: Inductance
Vb[V]: Power supply voltage
Vs[V] or less
N times
24VDC power
supply for
B
or
electromagnetic
brake
Conditions
1 - 5
Switch
VAR
U
Relay
Varistor
24VDC
U
B1
B
B2
Brake coil
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