Will a 4-wire resolver work?

Question

I am not an EE. Most resolvers I come across have 6-wires:

I have even come across 5-wire resolvers. Could we get this down to 4 wires?

For example, an RVDT (Rotary Variable Differential Transformer) requires only 4 wires: 2 for the primary coil, 2 for the secondary coils if they are wired in series.

Of course, with RVDTs, the secondary coils run parallel to each other.

What if the secondary coils were wired in series, where the secondary coils were perpendicular to each other like in a resolver?

Could I still determine the angle of the rotor?

Answer 1

You can get down to 4 wires, if you have star or Y connected 3 windings, and you have steel rotor, and you calculate the inductance of the windings. Assuming you have a microcontroller smart enough to read such a thing - use AC signals at high frequency to messure inductance, rather than slow signals that are used in your examples. And either read the windings one by one or try to use different AC frequencies on each winding.

3 wires if you have delta connected 3 winding, but reader is more complex - adc and dac on the same outputs. And reading is more complex too - need to account for a long path too

Answer 2

Could we get this down to 4 wires?

Yes. If each coil has one end connected to ground, you would have only 4 wires, sine, cosine, rotary and ground. Obviously, however, the circuit that interfaces with such a 4 wire resolver needs to supply and interpret single ended signals appropriately.