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Rewinding a submersible motor requires accuracy, insulation care, and proper winding calculations because the motor operates underwater and must be fully sealed against moisture. Below is a clear step-by-step guide.

Tools and Materials Needed

  • Copper winding wire (correct gauge)
  • Insulation paper
  • Slot wedges
  • Varnish
  • Multimeter or megger
  • Bearing puller
  • Coil winding machine
  • Heat gun or oven
  • Soldering materials
  • Insulation tape
  • Vernier caliper

Step-by-Step Guide to Rewind a Submersible Motor

1. Disassemble the Motor

Carefully remove:

  • Pump coupling
  • Bearings
  • Rotor
  • Stator cover

Mark all parts before removing them so reassembly becomes easier.

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2. Record Old Winding Data

Before removing the burnt winding, collect:

  • Number of slots
  • Coil pitch
  • Wire size
  • Number of turns
  • Connection type (Star or Delta)

This information is very important because the new winding must match the original design.

Important Motor Formula

N_s=\frac{120f}{P}

Where:

  • (N_s) = synchronous speed
  • (f) = frequency
  • (P) = number of poles

Example:

  • 50 Hz, 2-pole motor = 3000 RPM
  • 50 Hz, 4-pole motor = 1500 RPM

3. Remove the Burnt Coil

Heat the stator slightly to soften the varnish, then:

  • Cut the old winding
  • Pull out coils carefully
  • Avoid damaging stator slots

Clean all slots thoroughly afterward.

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4. Insulate the Stator Slots

Insert fresh insulation paper into all stator slots.

Good insulation prevents:

  • Short circuits
  • Ground faults
  • Water damage

For submersible motors, insulation quality is extremely important.

5. Wind New Coils

Use the correct copper wire size and turns count.

The coils should:

  • Be evenly wound
  • Have tight turns
  • Match the original coil dimensions
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6. Insert Coils into Stator

Insert the coils carefully into the slots according to the winding diagram.

Secure them using:

  • Slot wedges
  • Insulation paper
  • Lacing cord

Avoid damaging the wire enamel during insertion.

7. Connect the Windings

Connect the coils based on:

  • Single-phase configuration
  • Three-phase Star connection
  • Three-phase Delta connection

Star Connection

V_L=\sqrt{3}V_{ph}

Delta Connection

I_L=\sqrt{3}I_{ph}

Check continuity with a multimeter after connection.

8. Test the Winding

Perform:

  • Continuity test
  • Insulation resistance test
  • Phase balance test

Use a megger to ensure insulation resistance is high enough.

A good submersible motor winding should have strong insulation because water leakage can destroy the motor.

9. Apply Varnish

Dip or coat the winding with insulating varnish.

Benefits:

  • Prevents moisture entry
  • Improves insulation
  • Holds coils firmly
  • Reduces vibration

Then bake the stator in an oven to dry the varnish properly.

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10. Reassemble the Motor

Reinstall:

  • Rotor
  • Bearings
  • Seals
  • Covers

Ensure all seals are tight because submersible motors operate underwater.

11. Final Testing

Run the motor and check:

  • Current draw
  • Heating
  • Noise
  • Vibration
  • Insulation resistance

If the current is too high or the motor heats excessively, recheck:

  • Turns count
  • Wire gauge
  • Coil connections

Common Causes of Submersible Motor Failure

  • Water entering the winding
  • Overloading
  • Dry running
  • Poor insulation
  • Wrong rewinding data
  • Bearing failure
  • Voltage imbalance

Important Rewinding Tips

  • Always copy original winding data before removing coils.
  • Use high-quality copper wire.
  • Never reduce the wire size.
  • Replace damaged bearings and seals.
  • Use waterproof varnish for submersible motors.
  • Test insulation before installation.

Keywords

  • Submersible motor rewinding
  • Electric motor winding
  • Submersible pump repair
  • Three phase motor rewind
  • Motor insulation testing

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