Motor windings

Bipolar, Unipolar, Monofilar, Bifilar - what does it mean?

In principle a stepper motor has four windings (coils) They can be connected as follows:

• 4 leads - two coils in serial
• 4 leads - two coils in parallel
• 5 leads - on common wire
• 6 leads - two common wires
• 8 leads - all coils are separate terminated

Monofilar

The coil is wound with only one single wire.

Bifilar

The coil is wound with two wires in parallel.

Unipolar

The voltage on the coil has always the same polarity; the current through the coils goes always in the same direction.

Bipolar

The voltage on the coil changes in polarity; the current through the coil can change direction.