Protecting The Contacts Of Relay Outputs - ABB ACS380 Hardware Manual

Protecting the contacts of relay outputs

Inductive loads (relays, contactors and motors) cause voltage transients when
switched off. The voltage transients can connect capacitively or inductively to other
conductors and cause a malfunction in the system.
Use a noise attenuating circuit (varistors, RC filters [AC] or diodes [DC]) to minimize
the EMC emission of inductive loads at switch-off. Install the noise attenuating circuit
as close to the inductive load as possible. Do not install a noise attenuating circuit at
the relay output.
1 Relay output
2 Varistor
3 RC filter
4 Diode
1
230 V AC
2
230 V AC
+ 24 V DC
Planning the electrical installation 59
3
4