Using auxiliary contacts of 3RB / 3RU overload relays for switching large power contactors
QUESTION:
Switching large power motors in hazardous
areas:
For controlling magnet coils of strong power contactors, can coupling relays be
put in between the switching contacts of the 3RB / 3RU overload relay or does
the 95/96 contact of the 3RB/ 3RU have to be switched directly into the control
circuit of the contactor?
ANSWER:
As
regards controlling power contactors with 3RB / 3RU overload relays, the
following statement is valid:
If the power consumption of the contactor coil to be controlled exceeds the ON
and OFF switching capacity of the 3RB / 3RU overload relay, then an additional
contactor or relay with sufficient switching capacity can be used as an
interface for strengthening the contacts. This is also valid for applications
for motor protection in hazardous areas.