Motor Fails to Start

Check feed connections to control system and from control to motor.

Due to the control panel’s easy access, it is the most common place to first check for voltage to the motor. The top terminals of motor starter contact, if no voltage you can easily jump to fuses, knife switch etc. But the first check is visual for motor contactor overload being tripped. If it was, you could click on “Overload” diamond to read more troubleshooting advice there. Likewise during initial visual check, you can note if motor contactor is engaged. If not, you can check motor contactor coil for voltage. (If no voltage to coil, you can trace back in schematic, possibly it may lead you to missing run signal in PLC. If while checking voltage on each phase, one leg is missing, you could read more advice at “Single Phasing at Motor Starter” diamond. If not one of the previous mentioned, go to the next diamond you have not explored yet. They are in order from left to right, most common to less common.

TIP: If overload was tripped or fuse blown, don’t just reset/replace and walk away. You need to find out why the overload tripped or fuse blew.

Check source of power. Check overloads, fuses, controls, etc.

Check voltage supply and ascertain that voltage remains within 10% of the rated voltage shown on the motor nameplate.

Compare connections with the wiring diagram on the motor nameplate.

Tighten all connections.

Try to start motor under no-load conditions. If it starts mechanical load on motor may be too high. Ambient temperature too high. verload may be defective, or winding may be shorted or grounded

Check capacitor, if bad, replace.

Brushes may be worn, dirty or incorrectly fitted.