JCB High Inrush / Motor Starting Issue

Generator trips its main breaker when large motor loads start, even though total kW is within rating.

Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

Possible Causes

Undersized generator for motor starting kVA, Breaker magnetic trip set too low, Weak voltage regulation, Motor starting method (DOL instead of soft start)

How to Fix / Troubleshooting

Safety: Only qualified electricians should adjust breaker settings or motor starters.

Review load profile: Identify large motors and their starting currents. Compare to generator kVA and alternator subtransient reactance data.
Stagger starts: Configure controls so large motors do not start simultaneously.
Breaker settings: Check that the main breaker instantaneous trip is set appropriately for the generator's short‑term capability.
Motor starters: Consider installing soft starters or VFDs on large motors to reduce inrush current.

Repair Difficulty

Hard 4/5

Required Part

Main Circuit Breaker

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