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General Information on AC Servomotors
2.2 Mounted/integrated components
ALS
Preventing switch–
off voltage spikes
Fig. 2-10
Recommended external power supply for the holding brake
ALS/2-28
The basic voltage characteristic is shown below:
V
B
Fig. 2-9
Voltage characteristic when braking
When switching–off, the voltage spike V
millisecond range if the contactor is not dampened. The coil, contacts and elec-
tronic components could be destroyed. The switch contacts arc at switch–off.
This means that when switching–off, the current must be reduced using contac-
tor damping circuitry, which then also limits the voltages.
Caution: Sensitive electronic components (e.g. logic components) could howe-
ver be destroyed by the lower switch–off voltage (e.g. 60 volts).
For DC power supplies with a residual ripple <10%, the following diagram
shows the possible damping possibilities to prevent damaging switch–off
voltage spikes:
Motor
1–3
R1
D1
1
2
3
M
2
t
11
t
1
VB
V
Vmax
V
Vmax
can reach several 1000 volt in the
Vmax
F
Fuse (NCB)
K1
Contactor to switch the brake
S1
Holding brake
1–3
Circuit recommendations, refer below
D1
Diode
R1
Resistor
R2
Varistor
Z1
Zener diode
Siemens AG 2000 All rights reserved
SIMODRIVE Planning Guide Motors (PJM) – 11.00 Edition
09.00
Rated torque
Response delay
Closing time
Operating voltage
Max. switch–off
voltage
6SN1197–0AA20
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