As we mentioned before, we’ve chosen one of the asynchronous machine models.
The model needed a few adjustments.
Model parameters: % Example 3-1 File Name EX3_1.m % Calculation of Initial Conditions % Induction Motor Parameters Rs=1.77; Rr=1.34; Xls=5.25; %default: 5.25 Xlr=4.57; %default: 4.57 Xm=139; %default: 139 Jeq=0.025; p=2; %default: 4 % Steady State Operating Condition f=66.7; VLLrms= f * 7.6 * sqrt(3/2); s=0.0172; % Variable Voltage f=66.7; VLLrms= 460; s=0.0172; % Fixed Voltage Wsyn=2*pi*f; % synchronous speed in electrical rad/s Wm=(1-s)*Wsyn; % rotor speed in electrical rad/s
The first test we performed was just to run it and see some behavior at high-speed.
We have two options in voltage control: constant voltage (u = 380 V) and variable voltage (u = f*(380/50)).
If we use variable voltage, the speed growths sharply, but at the start of the modulation the torque is very high and at the huge speed (140k rpm), it can reach thousands.
If we use constant voltage, the speed growths gradually and the torque has much fewer numbers. Also, we have to wait more time to reach the desired speed. But to achieve such results we also need to change the reactance.
The formula was calculated by default state in which the voltage equals 380 V with frequency 50 Hz. By dividing, we got a coefficient of 7.6 (380/50).
Figure. Torque and Speed at 33.3 Hz, 333.3 Hz, 1333.3, 2333.3 Hz. Variable Voltage
Figure. Torque and Speed at 33.3 Hz, 333.3 Hz, 1333.3, 2333.3 Hz. Fixed Voltage
Conclusion of the results is – we can use only Fixed voltage due to unacceptable high variable voltage at very high speed.
Also, we need to come up with a solution for materials for coils, because as you can see, decreasing reluctance leads to the system becoming stable much faster.