Planning the electrical installation
72
WARNING! The Safe Torque Off function does not disconnect the voltage of the
main and auxiliary circuits from the drive. Therefore maintenance work on electrical
parts of the drive or the motor can only be carried out after isolating the drive system
from the main supply.
Note: It is not recommended to stop the drive by using the Safe Torque Off function.
If a running drive is stopped by using the Safe Torque Off function, the drive will stop
by coasting. If this is not acceptable eg, causes danger, the drive and machinery
must be stopped using the appropriate stopping mode before using this function.
Note concerning permanent magnet motor drives in case of a multiple IGBT
power semiconductor failure: In spite of the activation of the Safe Torque Off
function, the drive system can produce an alignment torque which maximally rotates
the motor shaft by 180/p degrees. p denotes the pole pair number.
Implementing the Power-loss ride-through function
The Power-loss ride-through function is activated when parameter
47.02 UNDERVOLTAGE CTRL is set to ON (default in Standard Control Program).
Note: If the drive is equipped with a line contactor, it opens in a power loss and must
be closed again by a time relay.
+24 V
XSTO:1
XSTO:2
XSTO:3
XSTO:4
U2/V2/W2
Control
circuit
UDC+
UDC-
ACS850-04
Output stage
(1 phase shown)
Safe Torque Off
connection on JCU
Activation
switch
Notes:
• The contacts of the activation switch must
open/close within 200 ms of each other.
• The maximum cable length between the
drive and the activation switch is 25 m
(82 ft)
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