Resolver error, error compensation, technical background information

Question:
How serious the resolver error and which compensation does Lenze offer?

Answer:
The resolver is based on inductive measuring using the transformer effect:

• A reference coil rotates in the magnetic field of two coils shifted by 90° (sine and cosine coil).
• The reference signal is transmitted contactless by induction (transformer effecct).
  

As in any other feedback system, the rotor shows differences between the actual and the detected rotor position. Normally, this is up to ± 10...20 angular minutes.

Note:
The manufacturer (Tamagawa) of the resolvers used by Lenze checks and preselects the resolvers for a max. difference of ± 10 angular minutes on a reference hardware,  i.e ± 10 angular minutes are valid only for resolvers bought from Lenze!
The resolver error is an absolute difference of the rotor position within a revolution, i.e. the error does not add up, see diagram. The error characteristics of each resolver are different.

Resolver error compensation:
Lenze offers a reduction of the resolver error of up to 2/3 for controllers 9300 together with Lenze servo motors. The characteristic of the resolver error is shown as a Fourier series consisting of the first and second harmonic. The resolver error can be compensated with the coefficient for phase and amplitude of these two harmonics. A number on the motor nameplate which contains these coefficients of the resolver as a code, must be entered under code C416.

Example: RS 23 67 43 78

• 23: First harmonic, amplitude
• 67: First harmonic, phase position
• 43: Second harmonic, amplitude
• 78: Second harmonic, phase position
  

If this number is not available the maximum difference must be assumed for the static position accuracy of the resolver. In practical applications, the pure resolver error can be neglected because of considerably higher mechanical tolerances of the entire drive system.