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90 Guidelines for planning the electrical installation
WARNING!
If DTC motor control mode is in use, do not open the output contactor while the drive
controls the motor. The motor control operates faster than the contactor, and tries
to maintain the load current. This can cause damage to the contactor.
When you select the DTC motor control mode and the motor coast stop mode, you can
open the contactor immediately after the drive has received the stop command. This is the
case also if you use the scalar motor control mode.
Protecting the contacts of relay outputs
Inductive loads (relays, contactors, motors) cause voltage transients when switched off.
The relay contacts on the drive control unit are protected with varistors (250 V) against
overvoltage peaks. In spite of this, it is highly recommended that inductive loads are equipped
with noise attenuating circuits (varistors, RC filters [AC] or diodes [DC]) to minimize the
EMC emission at switch-off. If not suppressed, the disturbances may connect capacitively
or inductively to other conductors in the control cable and form a risk of malfunction in other
parts of the system.
Install the protective component as close to the inductive load as possible. Do not install
protective components at the relay outputs.
1
Relay output
2
Varistor
3
RC filter
4
Diode
230 V AC
1
230 V AC
+ 24 V DC
2
3
4
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