# does the rotational port S recognize the load flow?

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K on 15 Sep 2023
Commented: Nathan Hardenberg on 16 Sep 2023
Hello,
for a projct I need to connect an asynchronous motor with a synchronous generator, which will supplement an island grid.
I used the rotational port S so I could add the clutch and a flywheel later, but I don't get the right load flow, from the motor to the generator, although the ASM is set as motor and SG as generator?
can anyone help me understand how the rotational port works? I didn't find informations in the documentation.
Regards,

Nathan Hardenberg on 15 Sep 2023
You can understand the rotational port as a welding joint with a rigid rotating rod. The rod beeing the "light green wire" in the simulink model. In the context of a motor, the rotational port would be the motorshaft, that can be connected to something. So if you want to connect the generator shaft with the motor shaft you simply have to connect both ports (see model below). The "Mechanical Rotational Reference" is a rigid rod that is not able to rotate. Every "rod" that is connected directly has the same rotational position,velocity and acceleration (and torque and inertia).
Hope that made it a bit more clear, but feel free to ask, if you do not unterstand something.
The model above should be what you need (if I understand correctly). But I am not really familiar with the Machine-Bocks, so take it with a grain of salt.
K on 15 Sep 2023
Hello,
I have two following questions:
1- if I specify the squirrel model 400V 50Hz 160kW and apply 50Hz 400V source then theoretically I should get a rotational speed equal 1487 rpm but that's not the case I get 1500 rpm which is wrong (for this I used your model)
when a converter is implemented to regulate the frenquency then the value should be 1500 rpm
2- the thing I still don't get either is when I use the same squirrel model and apply a load on the generator I get an electromagnetical torque of the generator like this
which is wrong assuming the electromagnetical torque of a generator should be negativ (actuallly it's partially wrong, the positive oscillation is wrong and should disapear, the neagtive one is right)
and the electromagnetical torque of the squirrel motor is also wrong
the motor torque should have a similar course as the one of the generator not constant
I tried various combination but it doesn't seem to work with the rotational port S
This is my model
I specified the torque of the motor as in the documentation
It would help a lot if anyone has an idea where is the problem.
Regards
Nathan Hardenberg on 16 Sep 2023
I unfortunately can't help with this regard, since it is much more specific to the machines/blocks