This story is very timely given the increased interest, and deployment of, energy efficient motors. I'll be writing about that, and about the results of a reader survey we did on energy efficient motors and drives, in the September issue of Design News.
Is the breakthrough the gains in efficiency when compared to squirrel cage designs? SRM's have been around for quite a while and the main problem associated with this technology has always been in the drive electronics - it is difficult to manage this type of motor without sophisicated controls.
An induction motor can only run below synchronous speed because the rotor field is generated by the slip speed between the stator and the rotor. The power used to create the rotor magnetic field is the loss mentioned by others. The strength of the induction motor is that as the load increases the slip also increases, which increases the current and magnetic field in the rotor. IT works well, but it uses more power than the synchronous motor. ON the other side, the synchronous motor is driven by the rotating magnetic field dragging the rotor magnets around. The problem with an ordinary synchronous motor is that when the load increases a point is reached where it falls out of synchronization and then stalls. This is great if you seek to have a very reliable means to limit torque, otherwise it is a problem. A hybrid motor that will continue to deliver torque as the load increases would be very handy, and it could probably be easier to control the speed with a VF drive. Also, it might wind up having a greater efficiency, which is a definite goal.
Is it possible to provide a more detailed description about how it provides this new function?
My experience with SynRM are that, by their nature, they generate significantly more torque ripple than an induction motor. Has this been remedied or did the author simply fail to mention it as a factor to be considered in selecting a SynRM for an application?
You do need a motor dive to operate a SynRM, but that type of drive is significantly less complex than a VVVF drive used for varying induction motor speed. They're not much more complex than 'soft-start' controllers. Given the dramatic reduction in the costs for all types of motor controls over the past 20 years, the cost of the drive electronics for a SynRM are going to be modest in all but the most cost sensitive applications. Additionally, the operating cost savings are likely to largely offset the cost of any drive electronics.
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