How to flash the field of a brushless generator

Written by tracy underwood | 13/05/2017
How to flash the field of a brushless generator
Generator (Digital Vision./Digital Vision/Getty Images)

A brushless electric generator relies on residual magnetism in the rotor to start building voltage in the stator. Once that happens, a small current flows from the stator into a field winding to induce full output power. But sometimes a generator loses the residual magnetism and fails to start producing power. This can occur when the generator sits unused for an extended period or if the user shuts it down under load. Generator repair shops use a special tool to flash the field of a non-functioning generator, but you can do it yourself with tools you may already own.

Start the generator. Check the circuit breakers. Reset them if they are tripped.

Insert the steel rod into the chuck of the corded drill. Tighten the chuck.

Insert the other end of the steel rod into the cordless drill. Tighten the chuck.

Plug the corded drill into the generator. Make sure both drills are set for forward (clockwise as viewed from the handle) rotation.

Hold both drills tightly. Press the trigger switch of the corded drill.

Press the trigger switch of the cordless drill, so that it spins the chuck of the corded drill. The corded drill acts as a small generator to feed current into the windings of the larger generator to magnetise the field and force it to start working. When this happens, the corded drill will start fighting against the cordless drill.


Keep a tight grip and be ready to release the switches immediately. The drills could injure you if they twist out of your hands.

Things you need

  • Electric drill (corded)
  • Cordless drill
  • Steel rod, 6mm by 100mm (1/4 inch by 4 inch)

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