Function Principle, Resolver
- Excitation winding
- Receiver winding 1
- Receiver winding 2
In the rear of the electric motor is a resolver whose function is to inform IEM (Inverter ERAD Module) about rotor position in all instances.
The resolver consists of a rotating cam disc with four cams mounted directly on the rotor shaft and a surrounding stator with 16 poles. The stator consists of three windings (one excitation winding, and two receiver windings) whose ends are connected to IEM.
Excitation coil
By means of the IEM providing an AC voltage with a frequency of 10 kHz through the excitation coil, a sine wave is created. The current in the circuit creates a magnetic field which in turn induces an AC voltage in both the sine and cosine coil.
Receiver winding 1 (sine coil)
The induced AC voltage in the sine coil is a mirror of that of the excitation coil until one of the rotor's cams passes the sine coil's magnetic field. The AC voltage is then modified to a "superimposed" sine wave.
Receiver winding 2 (cosine coil)
For the cosine coil as well, the induced AC voltage is initially a mirror of that of the excitation coil. When one of the rotor's cams passes the coil the signal is modified in the same way as for the sine coil. The cosine coil is offset 90° against the sine coil, so the signal will also be offset 90°.
The signals from the sine coil and cosine coil respectively are handled by IEM in order to calculate the rotor's current position. By comparing two signals with different characteristics, the reliability of the signals can be determined. The excitation coil's signal is also used as a reference in order to determine whether the signals from the sine coil and cosine coil respectively are reliable.
Diagnostic trouble codes are generated if any signal disappears or shows abnormal behavior.