# alternative names of the same motor type discussion



## major (Apr 4, 2008)

*traction motor*



no_reluctance said:


> One I'd like to hear about is, why when used for traction...they start calling the motor a traction motor...is there some structural difference between a traction motor of a given size and a motor that powers a fan of the same size that specifying the type of motor would not address properly?


Hi no_,

I'll try to address some of these terms. But don't get hung up on a name. Lots of folks don't know what they're talking about and some other areas or hobbies adopt entirely different vocabularies. 

I answered about traction motor a while back:


major said:


> The forklift industry where the vehicle has multiple motors has always referred to it as the traction motor. Other motors will be pump motors and auxiliary motors or power steering motor, etc. Traction motor means propulsion motor, sometimes called a drive motor.


More later,

major


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## major (Apr 4, 2008)

*DC-Inverter motor*



no_reluctance said:


> Firstly, an example I found ( a DC-Inverter motor) : http://www.chiltrix.com/FAQ.html
> 
> I'm 80% certain these guys are talking about a brush-less DC motor (BLDC from here on out) they go on elsewhere at length to express the inverter is inverting AC into the necessary drive frequency for the motor and using PWM to throttle...sounds like bldc to me. Its almost a doubly wrong name though, not only is it NOT inverting DC, but an inverter usually implies the opposite of a state..so AC-DC or DC-AC. though in practice AC-DC is usually called rectification because of the name of the circuits that perform that function. Though, I want to ask, because I can always be wrong.


I took a look at that web site. Basically, I don't think they know what they're talking about when it comes to motors. I've never seen that particular terminology. AC induction motors (ACIM) (NEMA spec) come as "inverter duty", having higher voltage insulation and other premium features suitable for VFD applications. DC-Inverter???? They're all converters; rectifiers (AC to DC) and inverters (DC to AC). DC-Inverter is redundant, isn't it? Who knows? Don't worry about it. You may never see it again.


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## major (Apr 4, 2008)

no_reluctance said:


> More generally however, I wanted to highlight the absurd number and breadth of alternative names for the same kinds of motors, and how those names, instead of doing justice, seem to actually do harm to the unity of misunderstanding that is the field of electronics. Firstly, the _brush-less_ part of bldc is great...it totally doesn't have brushes. the DC part... not so much. Its definitely not steady state DC as we think of that comes out of a battery..and a square wave is still an alternating kind of power... it would be better to call them permanent magnet AC motors, as some do. in that vein though...VFD motors seem to mean an AC motor with slip rings but obviously that can vary the input frequency and it affects the output of the motor speed. this is reasonable. but can we not call that an asynchronous AC motor?


VFD = Variable Frequency Drive. A controller for an AC motor where speed is dependent on frequency. These VFDs are typically used with induction motors, ACIM, which are asynchronous machines. Typically (almost always) these ACIMs will have squirrel cage rotors meaning no slip rings or brushes. 

BLDC are brushless. And in the view of most, require AC. Typically the inverter is fed with DC and sometimes actually contained within the motor, so called DC. The conventional VFD is intended to connect to the mains (AC power from the utility company, 60 or 50Hz). The first thing the VFD does is rectify the incoming AC to DC on the link. Then filters it and converts it to AC (inverts) to power the motor. The BLDC controller does the same thing.

There is also the PMSM, Permanent Magnet Synchronous Machine (or Motor). On the surface it looks like a BLDC. Some say there is no difference. Others insist that the they are commutated or switched differently and hence are wound a bit differently. BLDC is often a square or trapezoidal wave using hall sensors. PMSM is usually sine wave and may or may not use velocity/position feedback.


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## no_reluctance (Mar 13, 2014)

Yeah, thanks for the input, looks like I'm out of luck and there will always be a deeper level to go before one can be assured of the logical/structure scheme of a motor when it comes to the types that run off an alternating drive signal. I guess I just wish it were easier because, it seems to me that in the march of technology....pretty much all motors are converging on the brush-less AC type electrically commutated motors. pool pumps, washing machines, Air conditioning units, and of course...vehicles all seem to be converging on this type of motor. The only design question that does not seem to be definitively answered is how to get the rotor to magnetize. For this we've got the DC magnetic field in the DC motor. which is the most theoretically efficient since you aren't wasting power to maintain it. but they have problems retaining the field at high temps...and they are limited by the strength of the permanent magnets...likewise you cannot throttle the field strength so your eddy current loss is always fixed and IMO. a slip ring type could squeeze more actual power out of them for a given weight. though I've yet to see a definitive for or against evidence of this in cars. Then of course there is the much touted switched reluctance motor....nice and cheap and efficient, good at high temps. but which looks like it will probably be unsuitable for cars because of the cogging problem. I don't know how a user like eldis effortlessly glosses over these seemingly show-stopping details about motor controll for his universal controller. seems like it outta be simpler to intrinsically understand and express exactly what kind of motor is in the name.


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