Klockner Moeller Electric Parts from KlocknerMoeller.net

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All about Motors
Motor protection

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).