Failure rate of electric motors

[bob ward]

I was chatting today with a service guy from one of our major importers and resellers, of lathes & mills from small to large, drill presses, woodwork machinery etc. One thing he said in passing, which I thought was interesting, was that they have about a 5% failure rate in electric motors, presumably during the 12 month warranty period.

One train of thought from this is that a 5% failure rate seems very high. Electric motors are old and proven technology, I would have thought that .1% or 1 in 1000 failures would be more appropriate. Any input on what failure rates should be for well made electric motors?

Another train of thought is about the business model that this company is using. Obviously the motors on their machinery are poorly made, but they put up with it. It must somehow be cheaper or at least easier for the company to replace 1 in 20 of the motors on the machines they sell each year, and they sell thousands, rather than insist, (and presumably also spend another 3 or 5 dollars per motor), that their machines come fitted with motors that have say a 1 in 1000 failure rate. To me that seems to be a weirdarse business model but it seems to work for them. Any thoughts on why it is so?

[cuemaker]

I would guess a major factor would be where and who made the motor..

USA Baldor I assume would have a lower failure rate that a Chinese made..

[JCD]

I was in electric motor manufacturing for 30 plus years. Domestically, early motor failure rate can be measured in parts per million, not parts per hundred.
Although they appear very simple, electric motor manufacturing requires very close tolerances and good manufacturing process control. The Chinese have not yet perfected motor manufacturing techniques to a point that they produce a consistently reliable motor. Trey will get there eventually, but in the mean time, you'll get what you pay for.

[EddyCurr]

Any thoughts on why it is so?Perhaps they factor in free trouble-shooting & labour (the customer's)
for motor replacement into their Risk Management algorithm?

If warranty stipulated a service tech made as many site visits as
it took to resolve issues, then quality in the factory or along the
supply chain would likely improve.

.

[Richard-TX]

I was chatting today with a service guy from one of our major importers and resellers, of lathes & mills from small to large, drill presses, woodwork machinery etc. One thing he said in passing, which I thought was interesting, was that they have about a 5% failure rate in electric motors,

What is missing from this factoid is some details. Was he referring to single phase fractional hp motors? Are 3 phase motors included? What sort of failures? Bearings? Switch if 1 phase? Windings? Shaft?

[lazlo]

That's ~ 2 Sigma failure rate -- that's horrible for just about any industry.

Like JCD says, a quality western or Japanese motor will have wildly better failure rate.

[gnm109]

I was chatting today with a service guy from one of our major importers and resellers, of lathes & mills from small to large, drill presses, woodwork machinery etc. One thing he said in passing, which I thought was interesting, was that they have about a 5% failure rate in electric motors, presumably during the 12 month warranty period.

One train of thought from this is that a 5% failure rate seems very high. Electric motors are old and proven technology, I would have thought that .1% or 1 in 1000 failures would be more appropriate. Any input on what failure rates should be for well made electric motors?

Another train of thought is about the business model that this company is using. Obviously the motors on their machinery are poorly made, but they put up with it. It must somehow be cheaper or at least easier for the company to replace 1 in 20 of the motors on the machines they sell each year, and they sell thousands, rather than insist, (and presumably also spend another 3 or 5 dollars per motor), that their machines come fitted with motors that have say a 1 in 1000 failure rate. To me that seems to be a weirdarse business model but it seems to work for them. Any thoughts on why it is so?

I agree that 5% might be a high failure rate if every motor were to be used correctly. Unfortunately, the manufacturer can't control how the motors are used. Some users may overload them (1/2 hp motor where a 2 hp motor is needed); use them beyond their duty cycle (continuous operation as opposed to intermittent); miswire them, etc.

If all of the variables were to be weeded out, then of course 5% is high. Otherwise, it's probably to be expected. I must have gotten some good motors for my equipment. I have several that have been used intermittently for more than 35 years with no failures. IIRC, I did have to replace one bearing in a 1/2 HP Baldor but it's arguable whether a bearing failure is the same as a motor failure.

.

[Tony Ennis]

Cost engineering.

The name of the game is to make a motor that lasts juuuuuust longer than the warranty.

[lazlo]

The name of the game is to make a motor that lasts juuuuuust longer than the warranty.

That's true if you don't care about brand value.

[Tony Ennis]

Depends upon the length of warranty, doesn't it?

Baldor warranties range from 1 to 10 years.

edit - I checked the Griz site, all motors there regardless of size have a 1 year warranty.

[Dr Stan]

While the topic of these videos is chainsaws, it certainly applies to electric motors.

http://www.youtube.com/watch?v=kaMrtW1r8-c
http://www.youtube.com/watch?v=nU1bIsCdluQ
http://www.youtube.com/watch?v=7oIfAafqzOg
http://www.youtube.com/watch?v=0xKrkFMy_Z4

[lazlo]

Depends upon the length of warranty, doesn't it?

Baldor warranties range from 1 to 10 years.

Right, but when have you ever had a Baldor motor die on you? I have several, and they're extremely well-made. That's brand-value.

[Tony Ennis]

No argument. So if good motors last for 20, 30, or more years, why are the warranties relatively short? To remove liability from the books?

[Black_Moons]

Big question: Does this count actual motor failure, Or start/run capacitor failure? :P
Cause I can FULLY believe in 5% capacitor failure in 1 year on chinese motors.
For some reason they never bother includeing capacitors worth a damn.

For actual mechanical failure id think it would be much lower, like 1% or less.

[Forrest Addy]

Yes budget priced motor driven import machinery have far too many motor problems. I've investigated more than a few import motor failures. ALL fried. Most every import motor I've had the endbell off of never received the final step of stator manufacture, the final dip and bake that staurates the windngs with a tough encapsulation of insulating varnish.

If the windings can buzz from the magnetic fields the insulation can chafe, the wires short together, and fry the motor. One shorted turn will cause a progressive failure with plenty of smoke. All domestic motors I have seen (thousands) have been dipped and baked.

So there it is. Import motors are usually well designed but when an essential manufacturing step is omitted for whatever reason they will fail. As was said earlier. Premature failure rates shuld be ranked in units per million not hundreds. Why failures of 10,000X the expectation? Omission of the final dip and bake.

So you elected to purchase a motor driven import machine. Your very first step in comissioning the machine is to investigate the motors. Open them and examine the windings. Can you separate the windings with a probing thumbnail? If so remove the motor and take it to the motor shop. Have them dip and bake the stator.

By doing so you will have extended the life of the motor from weeks to generations. It will cost about $30 if you give them the bare stator, and $60 if you give them the whole motor. By doing so you will have avoided a week's delay arguing with customer service, shipping costs and time en route, RMA numbers etc.

Ideally you shouldn't have to monkey with it but if you buy cheap, you have to deal with these little problems. In any case its far better to anticipate failure and finesse it than to blandly let it happen then have to cope with the mess and delay.

[ammcoman2]

Forrest, I have been retired for 10 years now so I am not up to date anymore. However, back then the US appliance motor manufacturers were using a coating on the windings that did not require the "varnish dip & bake" cycle. The stators were merely heated after winding and blocking (compacting) and this "set" the wires.

I wonder if this process is being used on all motors now and whether the lack of correct procedures is causing the problems you have observed: ie. quality control.

Geoff

[Forrest Addy]

Ammco

You're probably right. I did read of a wire insulating varnish that self-bonds and cures with post-winding heat. I went out to the shop and looked at a new Weg motor still in the box. Looks like the windings self-bonded that is stuck together. There's no apparent thickness or conformal coating from which I conclude: no dip took place before the bake Naturally you have to have magnet wire coated with the correct insulation for this handy little phenomenon to take place.

Regardless, the pre-emptive dip and bake seems to stave off the "import motor fries."

[The Artful Bodger]

On the other hand Chinese single phase 2HP motors as fitted to the very popular 12x36 lathe are very easy to fix..

If you cannot hear a loud 'clack' when the motor spins up the starter switch is pukaru. Otherwise, take the covers off the capacitors and replace the capacitor that is in a pool of molten wax.

My lathe goes better than it did when new and no longer pops the ciruit breaker during a slow wind up and all I did was replace one capacitor.

[J Tiers]

The Chinese have not yet perfected motor manufacturing techniques to a point that they produce a consistently reliable motor. Trey will get there eventually, but in the mean time, you'll get what you pay for.

I strongly disagree.

The chinese know perfectly well HOW to make a good motor. They CHOOSE not to do it.

I posted a link a while back to a report by CHINESE authors on chinese motors, in which thye commented that the lowest possible cost rules in china. They mentioned that this attitude affected both failure rate and average efficiency of chinese motors. We, in the form of Wal-Mart, taught them that, but I think the chinese had a head start on that particular attitude....

The chinese are one of the most "american" of all the various national groupings on earth, I think. Not in all ways, but in a LOT of ways..

[oldtiffie]

Without getting into the pros and cons of motors for various applications from various countries as well as methods of manufacture etc. the fact is that when you bought the machine - new - you accepted the warranty.

It was a risk that the supplier had to honor on behalf and as the agent of the manufacturer.

In short, all things being equal and providing there was no abuse and any other deterioration was only the result of "fair wear and tear" the risk was with the supplier during the warranty period but shifted to the buyer after expiration of the period of the warranty.

The supplier and buyer are presumed to have dealt at arms length with no coercion and have each made an informed choice and decision.

The buyer's risk is just how well and for how long the motor lasts under its designed or designated use and purpose.

Repair and replacement of the machine and motor/s etc. should be included in a maintenance and replacement regime with costs factored in accordingly.

It is quite possible that "down time" cost due to a motor failure and replacement could be many times the cost of a new motor or of having that motor re-wound or even modifying a machine and/or new motor to replace the old. It may well be prudent to have a spare motor "on the shelf" ready to go.

I am pretty well provided for as regards spares for my recently bought or current model machines or parts - but a lot isn't covered - its all part of the risk I take.

In the event of a motor or similar failure it may be good policy to at least consider replacing the whole machine. This may well be the case if a motor etc. is "special" to the machine and is very expensive or not available or is not made any more etc.

I have not had a recent "Chinese" motor failure, but many machines are not as used as many here are. I am aware that they are not or may not be as good or as reliable or as durable as some of the better named/branded USA/UK/OZ/European motors were up to say 5>10 years ago. Those companies may well have since "out-sourced" their recent product and for all intents and purposes they are "Asian" products with the attached risks.

Sometimes all the complaining and bitching is good for is "letting off steam" and if you get "wound up" in the process it is far from productive - or edifying either.

Sometimes you just have to "eat" it and get on with life.

[Bguns]

I agree with Tiffie here, a motor can be set on shelf, awaiting the Chinese spark show...

I have seen failed Chinese motors and control wiring...

The motor is fairly inexpensive, easy to replace with a better quality motor, and when replaced with a 3 phase and a VFD, a BIG improvement in machine operation and control.

Instant reverse/variable speed/ramp up/down, are just not features 99% of single phase motors can provide.

Trivial for a 3 phase...

Here in the States, a US motor replacement (machining wise) involves at most, a new V Belt pulley, due to us still running mostly inch motor shafts.....

The motor footplate holes are very close inch/metric.. possibly an adaper plate needs to be made...

[J Tiers]

The chinese motor problem is not by any means limited to single phase motors. it is just that you tend to see more single phase chinese motors.

So changing to a VFD and still putting a chinese motor on is not any sort of cure-all.

The article I linked previously was primarily discussing 3 phase motors. Apparently the chinese themselves admit that they make crummy motors with generaly lower efficiency and reduced reliability.

[Tony Ennis]

"The chinese are one of the most "american" of all the various national groupings on earth, I think."

+1