If either your industrial operations already use synchronous motors or if you are designing a new industrial process that could greatly benefit from the perks of a synchronous motor, probably you have given some thought about the guts of this type of motor.
Now let one of our fellow members of the community D.Ros tell you more about it. Enjoy!
As any electromechanical element, synchronous motor’s performance is greatly defined by good equipment specification and maintenance. However, you’ll recall that, different from any alternating current (AC) asynchronous machine, synchronous motors require direct current (DC) to be supplied to its fields’ windings.
Perhaps the first thing that then popped up into your mind was a conventional set of slip rings mounted directly on the motor’s shaft and some high maintenance carbon brushes, and maybe just then, aware of the disadvantage that having slip rings can be with the hassle of their high maintenance, you might have reconsidered not using synchronous motors any more.
Yet, since these motors have been the heart of many heavy duty industrial operations, much attention has been given to optimize its performance by adapting its electrical and mechanical architecture to its applications and easing its maintenance. That’s how they came up with a brushless field exciter (yes, you read it just fine —brushless—).
This brushless exciter works like an alternator, which basically is a generator with a rotating armature mechanically coupled to the shaft of the motor and a stationary field. So, instead of directly supplying DC current into the synchronous motor’s field windings, DC current is supplied to the alternator’s stationary field, which magnetically induces the alternator’s rotating armature, whose energy is then electrically transferred into the field windings of the synchronous motor.
Now you’re possibly thinking “but didn’t a synchronous motor’s field need DC to be supplied to develop the magnetic poles on its rotor and chase the alternating three phase current on its stator?” and you’re right, but that is where some power electronics kicks in, as part of the mechanical assembly of the alternator, a set of diodes are arranged into a three phase rectifier that converts the induced AC from the three phase windings into DC.
And then some silicone rectifiers (SCRs) are trigger to electrically connect the rectifying bridge’s output into the synchronous motor’s field windings at the optimal moment; ain’t that genius?
This technological development expanded the applications of synchronous motors into highly abrasive processes and explosive risk environments.
Furthermore, this technology can be retrofitted into existing slip ring synchronous motors. In conclusion, if the application demands a low maintenance and highly reliable motor drive, a synchronous motor with a brushless exciter will probably be worth the investment.
Thanks for sharing your knowledge D.Ros! What did you all think about his article? Let him know in the comment section.