# Exercise for Electric Motor

You will use pre made models in Simulink and change variables according to exercises.

##### Modelling, simulation and analysis of PMSM-machine with inertial load

When the rotor of the machine is rotating at constant speed and torque, the currents and voltages will be three phase AC. When the machine is at stand still, the voltages and currents will be DC. The data for the motor to be modelled in the following exercises is given below.

Motor to be modelled:

6SM107S-3000 (Note RMS values)

Torque constant KT = 1,6 Nm/A

Voltage constant KE=97 mVmin

Rated Torque 23 Nm

Winding resistance Phase-Phase 0.37 ohm

Winding inductance  Phase-Phase 3,6 mH

Rotor moment of inertia 104 kgcm2.

Motor pole no.6

Thermal time constant 40 min

Weight standard 32,5 kg

###### Exercise 1 No-load and short circuit tests

This exercise uses the simscape model: noload_shortcircuit_tests.slx. The purpose of the exercise is to adjust the parameters of the simulation model to the machine to be modelled. These tests is also performed on real machines to determine or verify the parameters of a machine e.g. the voltage constant.

a) Calculate the no load line voltage and the short circuit current at 1000 rpm.

b) At which speed  is it acceptable to short circuit the machine and why?

c) Choose the parameters of the machine model to match the machine data above and verify the choice with no load (open circuit) and short circuit test.

Guidelines: Adjust the parameter Ψ until the no load voltage becomes correct according to calculations in

a). Only two experiments is needed, why?  When the no load voltage is correct then also flux linkage Ψ is correct (for a certain pole number). After that a short circuit test at 1000 rpm can be performed to verify that the short circuit current becomes the same as in the calculations in a). This indicates that the impedance (or indirectly R, L) of the machine is correct. In a real machine the short circuit current would be too large and the speed should be reduced to value calculated in b), but this is a simulation.

d) Check the relation between the electrical and mechanical frequency.

e) Write a m- file in order to insert the model parameters automatically, to be used in upcoming exercises.

###### Exercise 2 DC-current excitation of the machine

Use the simscape model: DC_current_phasor.slx. Use the m-file you made to get the parameters for the machine model.

Inject the following current phasors (stator coordinates)

1)      10A

2)       j10A

a)      Compare the results and give a qualitative explanation.

b)      Measure the phase currents a, b, c and explain their relation to the current phasor in stator coordinates.

###### Exercise 3 Excitation with synchronous rotating current phasor (stator coordinates) = DC current phasor in DQ rotating coordinate system

This exercise uses the Simscape model: current_phasor_commutation.slx. Use the m-file you made to get the parameters for the machine model. In reality the machine is feed by current controlled voltage sources rather than current sources as in this example. We will study this more in exercises about control.

Inject the following current phasor in DQ-coordinates (rotating coordinates).

1) 10A (pure D current)

2) j10A (pure Q current)

Compare the results from 1) and 2)  and give an explanation of the behavior of  all the measured  mechanical and electrical quantities.

##### Cascade control for the simulated PMSM-motor

The PMSM machine from the actuator exercises is now to be used for cascade speed control. First the inner current (torque) control loop is tuned, after which an outer speed control loop is designed.

###### Exercise 4 Excitation with three phase voltages and current controllers

This exercise uses the Simscape model: current_control.slx. Use the m-file you made to get the parameters for the machine model.

In this exercise the current generators are replaced with voltage generators controlled by current PI-controllers and feedback of measured currents. The current feedback signal is filtered.

Adjust the PI controller, is it possible to eliminate the static error? It is not required to optimize the controller by e.g. pole placement, just to tune it by trial and error.

###### Exercise 5 Cascade control, design of speed loop

Use the Simscape model of the current controlled machine from the previous exercise and design an outer speed control loop.