How does a resolver work?

Resolvers work using the same basic physical principles as an electrical transformer. Resolvers typically use copper windings in its stator and a machined metal rotor. The inductive coupling between the windings varies according to the angular position of the rotor. The resolver is energized with an AC signal and the resulting output from the transformer windings is measured to provide an electrical signal which is proportional to angle.

How does a resolver work?

A typical resolver has three windings – a primary winding and two secondary windings. The windings are created using copper wire and are formed on the resolver’s stationery element – the stator. The primary wire acts as the input for an AC drive signal and each of the secondary windings are used as pick up or receive windings. In the diagram above, the rotor is made from a material such as steel or iron and is arranged relative to the windings such that it will couple varying amounts of energy into the secondaries depending on its angle of rotation.

Strengths and weaknesses of a resolver

StrengthsWeaknesses
Reliable, robust, accurate, long life, tolerant to misalignmentBulky, heavy, expensive, needs skilful specification and implementation