Phase Voltage not changing with field voltage in a synchronous motor setup.

Hello all!

I'm trying to build a circuit for use in simulating a synchronous motor. I've got some initial setup, and when I first run the simulation I get some variance in my values. However, after I run it a few times, the phase voltages don't change very far from 120VAC. Even if the field voltage is dropped to 50V. Can someone elaborate on what I may be missing? I've uploaded screenshots of the ciruit, and then the parameters of the motor.

This is showing Vf=120V and the V_Phase showing ~120V.

This is showing Vf=50V and the V_Phase showing ~120V again.

Here are the parameters currently in place.

The powergui was used to automatically calculate and determine the machine initialization variables as well. Any help is appreciated. Thank you.

Answer 1

[Joel Van Sickel]

Hello Martin,

I would guess there are 2 issues.

1: your load current is very load, so your machine isn't pulling any current. It is essentially an open loop test.

2: I'm not sure how realistic your machine parameters are. Do you really have a 5 ohm stator and 0.1 H inductances?

Regards,

Joel

[Martin Komm]

Joel,

I'm not sure what you mean by load current is very load.

Some takeaways, the goal of this circuit is to try to conduct something as similar to the open-circuit test, the short-circuit test, and the DC test. Insofar we haven't had much luck. If there is a better way to design this in simulink I'd love to hear suggestions.

The only other software we have available is Multisim, but it doesn't have the capabilities of simulating a synchronous machines (as far as we know).

[Joel Van Sickel]

Hello Martin,

ah, so you are intentionally having a low load (high resistance). Also, you didn't answer wether you actually have a 5 ohm stator resistance and 0.1 henry inductance for your machine.

Those types of tests are usually to characterize a motor, not to simulate it. One of the issues with them is that a typical lumped parameter model like you are using doesn't include saturation by default. Considering you are doing an open load test and a short circuit test, saturation effects would probably be important in simulating those situations accurately. This type of model is more intended for actual operation and not comparing the extremes.

Regards,

Joel

[Martin Komm]

I believe the armature resistance was measured ~12ohms. I'm not sure what the Xs would be, as I don't have the calculations on hand at the moment. We were using the values to just simulate something to get the students to be able to run some sort of simulation. I appreciate the answers, and I'll get with the professor about how to move forward.

Kind regards,

Martin Komm