12 - 2
12. SERVO MOTOR
12. SERVO MOTOR
12.1 Servo motor with a Lock
12.1.1 Features
CAUTION
The lock is provided for preventing a drop at power failure or at servo alarm
occurrence during vertical drive, or for holding a shaft at stop. Do not use it for
normal braking (including braking at servo lock).
The lock has a time lag. Use the lock so that servo motor control is started after the
lock has completely opened. Be sure to check the time lag of the locking with a real
machine.
Configure a lock operation circuit which interlocks with an external emergency
stop.
Refer to section 3.11 for details of the circuit configuration and the timing chart.
The servo motor with a lock 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 lock to
release the lock. Switching power off makes the lock effective.
(1) Lock power supply
Prepare the following power supply exclusively used for the lock. The lock terminals (B1, B2) do not have
polarity.
E
le
c
tr
o
m
a
g
n
e
ti
c
b
ra
k
e
Switch
VAR
B1
U
B
24VDC power
supply for
electromagnetic
brake
B2
E
le
c
tr
o
m
a
g
n
e
ti
c
b
ra
k
e
Switch
VAR
B1
U
B
24VDC power
supply for
electromagnetic
brake
B2
or
A surge absorber (VAR) must be installed between B1 and B2. Refer to (3) in this section for the selection
method of surge absorber, and to "Lock characteristics."
(2) Sound generation
Though the brake lining may rattle during operation in the low-speed area, it poses no functional problem.
If braking noise occurs, it may be improved by setting the machine resonance suppression filter or adaptive
vibration suppression control in the driver parameters. Refer to section 7.2 for details.
(3) Selection of surge absorbers for lock circuit
(a) Selection condition
Item
Conditions
24VDC
Varistor
Relay
Brake coil
U
Lock specification
R[
] : Resistance
L[H] : Inductance
Vb[V] : Power supply voltage
Desired suppressed
voltage
Vs[V] or less
Durable surge
application time
N times
lock
lock
lock
lock
Lock coil