Protecting The Contacts Of Relay Outputs - ABB ACS355 User Manual

If frequent bypassing is required, employ mechanically connected switches or
contactors to ensure that the motor terminals are not connected to the AC power line
and drive output terminals simultaneously.

Protecting the contacts of relay outputs

Inductive loads (relays, contactors, motors) cause voltage transients when switched
off.
Equip inductive loads with noise attenuating circuits (varistors, RC filters [AC] or
diodes [DC]) in order 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 I/O terminal block.
230 V AC
230 V AC
24 V DC
Varistor
RC filter
Diode
Planning the electrical installation 45
Drive
relay
output
Drive
relay
output
Drive
relay
output