BEMF Profile

How to specify Back EMF parameters in the Schematic Editor ?

Back EMF is a voltage produced due to a change in flux linkage as a result of motion. By the Faraday's law:

where is the instantaneous flux linkage. For a machine rotating at speed :

For a permanent magnet with flux linkage , the adimensional quantitydefined for each rotor angle position is the back EMF profile.

The PMSM block has a "Back EMF profile" parameter, in the "Electrical" tab, which is a dropdown. When the "User defined" option is selected, you are allowed to specify a file which should contain the Back EMF values in the “Back EMF profile table" field.

This file has to be in a specific format which is described below.

What is the format of the Back EMF parameters file ?

The Back EMF parameters are described in a JSON format. The following parameters must appear in the file.

Parameter (JSON key)	Value type	Unit	Description	Constraints	Example

Parameter (JSON key)	Value type	Unit	Description	Constraints	Example
backEmfValues	double[1024]	N/A	One dimensional array of the back EMF waveform values.	Value range must be between -1 and 1 Values are equally distributed over 360 degrees The number of values required is strctly 1024	`{ "backEmfValues": [ -0.0, -0.005, -0.01, [...] 0.01, 0.005 ] }`

All the examples above concatenated would give in a valid JSON format: