Before Opening An Output Contactor (In The Dtc Motor Control Mode); Relay Output Contacts And Inductive Loads - ABB ACS800 Hardware Manual

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Before opening an output contactor (in the DTC motor control mode)

Stop the drive and wait for the motor to stop before opening a contactor between the
output of the drive and the motor when the DTC control mode is selected. (See the
Firmware Manual of the drive appliction program for the required parameter
settings.) Otherwise, the contactor will be damaged.
In scalar control, the contactor can be opened with the drive running.

Relay output contacts and inductive loads

Inductive loads (such as relays, contactors, motors) cause voltage transients when
switched off.
The relay contacts of the RMIO board are protected with varistors (250 V) against
overvoltage peaks. In spite of this, it is highly recommended to equip inductive loads
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 the protective components at the terminal block.
Planning the electrical installation
Varistor
230 VAC
RC filter
230 VAC
Diode
24 VDC
Relay outputs
RO (NC)
RO (C)
RO (NO)
RO (NC)
RO (C)
RO (NO)
RO (NC)
RO (C)
RO (NO)