Can Reluctance Motor run without Frequency Converter and any Special Design changes?

This post will give you a very nice and never-mentioned-before idea of reluctance motor. So please read it, and let me know your opinion.

All the hype around Synchornous Reluctace motor is truly deserving. Couple of years back I had the pleasure to see almost 95% efficient reluctance motor by ABB in one symposium in Helsinki, and these days you will see even different reluctance motor design for Electric Vehicles. You are may be aware that with a clever rotor cage design in the reluctance rotor itself, you can start a reluctance motor from the grid. The question put up here is not addressing that kind of design (thats why its written as 'any Special Design changes').

So can you start just a simple reluctance motor from grid? Dear readers, coming back to the question, the answers is a big fat YESSSSSSSSSSSSS!!!! The video link given below shows how we managed to rotate the reluctance motor without any frequency converter directly from a power source.

I was little sceptic while running this crazy experiment as we had no controller but as they say fortune favors the brave. We did it at very low voltage , just to make sure of not ruining our machine. So now, if you are a control specialist, you are probably little furious. Indeed the starting of the motor is still behind with your state of the art speed controller. You are still a winner.

WHY IT HAPPENS?

It is the hysteresis of the rotor that is acting like a cage for the motor. To catch the hysteresis torque coming from the asynchronous field , you need to have a hysteresis model in your FE computation. Ideally, the torque is proportional to the integration of the loop area complied by the B-H loops in each rotor elements. We have implemented Presiach model and Zirka's model for our FE computational software (perks of being in an awesomely advanced material model lab), and tried to catch that torque. Let me skip the modeling part here, but to rephrase what I said in the simplest manner. When you start a normal Synchronous Reluctance Motor without any controller, it is acting like a Hysteresis Motor as there is a lag of induced field in the rotor from the stator. This is what will lead the acceleration from the blocked rotor state. Luckily we had active magnetic bearing while doing the experiment which cuts of the friction considerably, and a small torque was enough to start the motor.

WHAT ELSE!

I believe that there is a small contribution of hysteresis torque in the the torque ripple of the motor even when it is acting like a traditional synchronous reluctance motor. Cause the space harmonic are going to produce asynchornous field in the rotor and there by some torque at some level. But the effect is small and will be very difficult to detect from the numerical error. May be someday someone will invest time and money to verify that ripple. Till then, lets stay optimistic with this crazy idea of an invisible hysteresis motor inside a synchornous reluctance motor.

PS: We have a published an article based on this phenomenon little bit on an advanced machine. You can read it here. Feel free to share both the articles and give us your valuable feedback.