Learning Forum

[ranjanpal999]

I have used load torque as 0 Nm to simulate a motor in MAXWELL 2D environment. Here are the details:

 

The torque graph is as such and is perfectly fine:

 

However, if I apply 1Nm load torque, the electromagnetic torque does not meets the load torque and shows -1Nm electromagnetic torque  i.e. just the opposite of load torque.

Can anyone please suggest me where am I going wrong?

[Paul Larsen]

In this Mechanical Transient, the Load Torque is usually applied as negative, and is balanced in steady state (along with any damping) by the Magnetic Torque.

I suggest you look at both the rotor speed (is it above or below synchronous speed to be in generating or motoring mode, respectively?), and also to try using negative load torque.

For reference, the signs are all relative to the rotation axis with the right-hand-rule.  So, a positive direction is moving counter-clockwise around the Z-axis in a top-down view (normal XY plane view), and a positive torque will be in the same right-hand-rule direction around the axis.  If the load torque is positive, it means that the shaft is supplying power when the rotation is in the same direction (generating).  If the load torque is negative when the rotational speed is positive, it means that the shaft is receiving power (motoring).  You can make similar concepts for the magnetic torque (Moving1.Troque), but the value is opposite to the load here.

One additional suggestion, you might consider using an "if" statement to define the load torque to get it started faster.  You could give the shaft an initial kick in the right direction, and then apply the load by stating the LoadTorque as "if(time<0.2s, 1,-1)*1Newtonmeter", where the if statement switches the LoadTorque polarity after the initial push.  Then, you can scale the expression outside with a constant using units or with a variable.  That's just a thought.

[ranjanpal999]

Thanks a lot!

It has worked.