Motor Keeps Tripping the Overload Relay: Diagnosis

The overload relay protects your motor by tripping when current stays too high for too long. Frequent tripping is not a nuisance to bypass — it is the protection doing its job, telling you something is wrong. Here is how to diagnose it.

1. Genuine Overload

The motor is driving more load than rated — a heavy, binding, or increased load. Fix: Measure running current against nameplate; investigate why the load increased (worn bearings in driven equipment, process change, blockage).

2. Wrong Relay Setting

The overload relay set below the motor's full-load current will nuisance-trip. Fix: Set the relay to the motor nameplate full-load current (or 58% of it for star-delta starters, where the relay sees phase current).

3. Single Phasing

Loss of one phase overloads the remaining two — a classic repeated-trip cause. Fix: Check all three phases; many modern relays have built-in single-phasing protection.

4. Voltage Imbalance or Low Voltage

Unbalanced or low voltage raises current draw. Fix: Check phase voltages are balanced within 2% and at rated level.

5. High Ambient Temperature

A hot panel or hot location makes the thermal relay trip at lower current. Fix: Improve panel ventilation; use ambient-compensated relays.

6. Frequent Starting

Each start draws heavy current; too many starts trips the relay. Fix: Reduce start frequency or use a soft starter.

Never bypass a tripping overload relay — it is protecting a costly motor. Our team can diagnose the real cause and supply correctly-rated protection. Contact us or send a motor inquiry for expert guidance from our Mumbai and Ahmedabad teams.