# IPM vs Induction rotors, pros vs cons



## PStechPaul (May 1, 2012)

I was not sure what an IPM was, but I found some information here:
http://www.daikinpmc.com/en/energysaving/IPMmortor/index.html

Their claims are rather impressive, but I wonder how true they really are. It shows efficiency of 95% or better from 800 to 3600 RPM compared to 60% to 85% for a comparable ACIM, but that is not the whole story, as one must also factor in the torque at those speeds. IMHO, anything with a rare earth PM may be problematical, and it may be better to consider an SRM, or even better, an RSM (Reluctance Synchronous Motor) which uses the same stator as an ACIM, and can be driven by a standard VFD. See the following:





 
BTW, I am once again looking into an SRM and I have discussed the idea on another forum:
http://bbs.homeshopmachinist.net/threads/61983-Punch-and-die-for-thin-matal-(motor-laminations)
It started as an induction motor:
http://bbs.homeshopmachinist.net/th...-model-three-phase-AC-induction-motor-project


----------



## major (Apr 4, 2008)

> *Double duty*
> The key to Remy's HVH performance is Remy’s winding technology. If you seek maximum torque, power and efficiency, select our IPM (interior permanent magnet) rotor configuration. For simpler controls and cost advantage, use HVH with Remy’s AC induction rotor package. HVH’s ability to maximize cooling vs performance in oil or glycol systems is unmatched.


That is from the Remy web site. They offer both rotor types for their stators. For the most part, according to their engineers, efficiency difference is a point or two, give or take, depending on duty cycles. Cost is pretty big factor. And the control cost difference will really hit hard. Very few places offer a control for the IPM, and those who do will need the motor to tune and charge you an arm & leg.

Stick with your induction rotors or buy a complete IPM motor/drive package.


----------



## tylerwatts (Feb 9, 2012)

Gents, thanks for replying. I may have confused matters somewhat by stating IPM. I mean simply a permanent magnet rotor vs an induction rotor. Does this make any difference? 

PStechPaul 
Can you elaborate any more on the feasibility of making a custom switched reluctance rotor for an existing AC stator and what challenges might be present please? Also, what differences exist for control algorithms and hardware requirements please? I'll read and poach any useful info from your links shortly also. 

Thanks


----------

