What causes destruction of the overload relay?
Destruction will take place only in the
event of a short circuit on the load side of the relay
when the back-up fuse is rated too high. In most cases,
this will also endanger the contactor and motor.
Therefore, always adhere to the maximum fuse rating
specified on every relay.
3-pole overload relays should be so
connected in the case of single-phase and DC motors so
that all three poles of the overload relay carry the
current, whether in single-pole or 2-pole circuits.
| 1-pole |
|
2-pole |
 |
|
 |
An important characteristic feature of
overload relays conforming to IEC/EN 947-4-1 are the
tripping classes (10 A, 10, 20, 30). They determine
different tripping characteristics for the various
starting conditions of motors (normal starting to heavy
starting). |
