Keeping the Motor Rotation Speed Constant

Ms. Ori, I have a question for you.

What is it, Vex?

A customer asked me for a good way to keep a constant motor rotation speed. They use an inverter to drive the motor on their belt conveyor and the motor slows down when they place heavy objects on it, but I can’t figure out the reason.

Do you remember how inverter speed controls work?

Yes, the inverter changes the speed of the motor by changing the power supply frequency applied to the motor. That allows for speed regulation without feedback from the motor on the rotation speed.

That's right. If you look at the inverter's speed - torque characteristics, do you see how it shows that the speed decreases when a load is applied?

The speed - torque characteristics? You mean this diagonal line?

Yes, this diagonal line shows the torque characteristic at each frequency when the power supply frequency changes.
For example, if you look at the 50 Hz line, the motor's rotation speed is almost 1500 r/min when the torque is 0 N·m, but it drops to about 1300 r/min when the torque is 0.19 N·m.
Inverters don't supply feedback on the motor's rotation speed, so they don't adjust to the set rotation speed.

I see. That's why the customer said that speed decreases when heavy objects are placed on the belt.
So we should recommend a product that provides feedback on rotation speed.
I think an AC speed control motor would work well. They use a tachogenerator to provide feedback on rotation speed.

I would especially recommend Oriental Motor's new speed controller MSC-1.
Here's a comparison of speed - torque characteristics between the MSC-1 and conventional products.

Wow, the MSC-1 doesn't slow down even with additional torque.

As you can clearly see from the graph, even conventional types show little fluctuation in speed when torque is applied compared to inverters.
And MSC-1 has improved performance compared to conventional speed controllers.

The MSC-1 is amazing.

Also, compared to inverters and conventional speed controllers, it is much more compact, about the size of a business card.
The list price is 9,200 JPY, it’s more affordable, too.

I'm sure the customer will like it.

There are also brushless motors that provide feedback on rotation speed, so don’t forget to promote them as well.
The key points of the MSC-1 are high performance, low price, and compactness, brushless motors are high speed and high functionality, so be sure to explain the characteristics of each properly.

I got it. I'll call the customer right away.