Our software takes many different feedback devices and generates a common 'electrical angle' to show the position of the feedback. This allows technicians to follow a repeatable procedure for testing and setting alignment, regardless of the feedback type.
The electrical angle is the angle that occurs between each pole pair of a servomotor. Therefor, the electrical angle should repeat more than once in one mechanical turn of the shaft, depending on how many poles the motor has. For example, an 8 pole motor will have an electrical angle that repeats 4 times in one mechanical revolution. A 6 pole motor will have an electrical angle that repeats 3 times in one mechanical revolution.
The electrical angle is generated from several pieces of information provided by the user, mainly the motor poles selection and the resolution of the feedback device. If the user has not entered the correct number of poles or the feedback resolution is not correct, then the electrical angle will also not be correct. Below are some simple checks to make sure you have made correct selections.
- The electrical angle should repeat at each pole pair. For example, if an 8 pole motor is showing 200E degrees for a +U-V lockup, then that electrical angle should be close to the same at all four +U-V lockups around the motor.
- The electrical angle should change by 60E degrees between each adjacent line-to-line (L-L) lockup. (+U-V, -W+U, +V-W, etc). Also between each adjacent line-to-neutral (L-N) lockup (+U-V-W, -U+V+W, etc).
- The electrical angle should change by 30E degrees between each adjacent L-L to L-N lockup (+U-V, +U-V-W).
If any of these relationships are drastically off, it could indicate an issue with the motor windings, magnetic rotor, or feedback device.
The mechanical angle is generated only with encoder selections, as they have only one index position per turn. This angle should correlate with the physical position of the motor shaft. If not, then you may have the incorrect encoder resolution selected.
The resolver angle is shown only with resolver feedbacks and is generated directly from the output of the sensor. Resolvers can have one or multiple zero angles in one mechanical turn. We call these resolver speeds. If the resolver is a one speed, than the resolver angle is also effectively a mechanical angle. If the resolver has the same number of speeds as the motor pole pairs, then the resolver angle will be the same as the electrical angle. Again, the electrical angle should always be used for testing and setting alignment. For a correct electrical angle the resolver speeds and motor poles need to be set correctly in the software.
Technicians should always be using the electrical angle to record and set servomotor alignments. Mechanical angles and resolver angles are only provided as a reference. The only feedback sensors which do not generate electrical angles are Hall effect commutation pulses, as their resolution is too low to generate angles. They must be recorded using the H1-H6 commutation H, L, and toggle states (H/L or L/H) in reference to the motor lockup.
Below are some images that may help with understanding the relationship of these different angles.
Electrical Angles vs Mechanical Angles from Encoders
Electrical Angles vs Resolver Angles