For high-voltage motors, partial discharge during operation poses a critical quality risk to windings. Two key factors causing partial discharge are voltage and air gaps.

 

Based on theoretical calculations:

1.Motors with rated voltage >5.5kV risk partial discharge in winding insulation.

2.Dangerous air gaps (0.1-0.6mm) can trigger partial discharge even at lower voltages.

 

Key conclusions:

l Most 6kV+ motors experience partial discharge, as their typical air gaps range 0.05-0.5mm.

l All high-voltage motors (>15kV) risk internal discharge even with air gaps <0.05mm.

 

Insulation challenges in windings:

l Interturn insulation (thin & large contact area) endures extreme stress:

Ø Startup overvoltage (steep impulse waves concentrated on the first coil)

Ø Mechanical/thermal stresses during manufacturing/operation

Ø High-frequency voltage spikes in VFD-driven motors

 

Critical design safeguards:
1. Conductor selection:

Use F-class self-adhesive magnet wires (avoids thin/flat profiles prone to interturn failures).

2.Winding process control:

Reinforce insulation in the first coil (absorbs 50%+ of startup voltage surge).

3. Insulation-voltage matching:

Tailor insulation materials/layers to voltage levels (e.g., SBEFB mica-covered wires for 10kV, SBEMB film wires for 6kV).