Wiring Manual 2008 - Moeller

8
All about Motors
Engineering notes
Switching of capacitors
8-16
Moeller Wiring Manual 02/08
DIL contactors for capacitors – individual switching
Individual compensation Group compensation
L1...3
-F1
-Q11 -Q31
M
3
-M1
-C1
When capacitors are switched on, contactors are
heavily stressed by transient current peaks.
When a single capacitor is switched on, currents
up to 30 times the rated current can occur; these
can, however, be reliably switched by Moeller
DIL contactors.
When installing capacitors, the VDE
specification 0560 part 4 (Germany) and the
standards which apply to each country should be
observed. According to these, capacitors not
directly connected to an electrical device which
forms a discharge circuit, should be equipped
with a rigidly connected discharge device.
Capacitors connected in parallel to the motor do
not require a discharge device, since discharging
is performed via the motor winding. No
switch-disconnectors or fuses must be installed
between the discharge circuit and the capacitor.
A discharge circuit or discharge device must
reduce the residual voltage of the capacitor to
L1...3
-C1
-Q11
M
3
-M1
-F1
M
3
M
3
-M2 -M3
less than 50 V within a minute of the capacitor
being switched off.