# 200 volt motor



## MDShunk (Jan 7, 2007)

Volts goes up, amps go down. Sorta how it works.


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## JRaef (Mar 23, 2009)

MDShunk said:


> Volts goes up, amps go down. Sorta how it works.


Well, sort of, but it's a little different with induction motors in that if the voltage goes up ABOVE what the motor design rating is, the current will start to go up again. The relationship is kind of a "U" shape, I like this graphic to show it:









Note the shape of the "FL Amps" curve.

So to the issue at hand, typical NEMA motor design specs call for them to operate +-10% of the design nameplate voltage rating. But a 200V motor being fed with 240V is getting 20% over voltage, so extending that curve out beyond the limits of that chart, you will be seeing over 10% more amps per unit of load. Your efficiency has dropped quite a bit, as has your PF, and possibly most dangerous, your starting torque will be off the chart, meaning you could start damaging mechanical parts.

I would either change that motor out, or put in a buck transformer to drop it closer to 200V.


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## Wirenuting (Sep 12, 2010)

I use 200v motors on 208 systems only. The very few spots we have here with 240v sys have caused those 200v motors to die early.. They were mostly compressors. Our compressor guy loved the emergency OT he got for repairing them. He always said there were "problem" compressors. You can guess my reply to him.


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## Forge Boyz (Nov 7, 2014)

Thanks, guys. I was thinking that's the way it worked. I won't entirely rule out mechanical problems yet because it had been tripping overloads at the original location, but I have no idea what the source voltage is there.


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## Wirenuting (Sep 12, 2010)

Forge Boyz said:


> Thanks, guys. I was thinking that's the way it worked. I won't entirely rule out mechanical problems yet because it had been tripping overloads at the original location, but I have no idea what the source voltage is there.


Check the "unloading valve" also. If it sticks the start up can be a real motor killer. 
Depending on the style compressor, it may look like a scrader valve on the pressure switch. (Ya my spelling sucs)


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## Forge Boyz (Nov 7, 2014)

Unloader works. The fact the FLA rating is 30.1 and it's running about 35A is the real issue


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## John Valdes (May 17, 2007)

Whats the service factor? You might be okay.

But Patrick is correct in that a 200 volt motor can be run on 208, but its not recommended to run it at 230. Temporary yes. But don't sell it to anyone. You may end up buying them the correct motor and thus losing any money you/he made on it.
You did say the owner is compressor dealer?


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## Forge Boyz (Nov 7, 2014)

Yes. He only gave $350 for it on a trade in so he is fine with spending money on it. It is in beautiful condition cosmetically. He is using it in his own shop. After I told him the motor was a problem, I was second guessing myself and wanted some confirmation. Thanks for the input.


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## JRaef (Mar 23, 2009)

200V is the designated "Ultilzation Voltage" (meaning motor design voltage) for a 208V Distribution Voltage as delineated in ANSI and NEMA standards. Just as 230V, 460V and 575V are the motor design voltages for 240, 480 and 600V Distribution Voltages. But in 10HP and below, most motor mfrs use a compromised design that allows their 230V motors to be used at 208V. But when someone buys a motor designed as 200V you can't use that on 240V systems. That's usually only done by equipment OEMs who want you to buy a different motor from their service dept if you move so they can charge you for it.


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## Jhellwig (Jun 18, 2014)

You could put an inverter on it. That would be an easy way to go from 240 to 200 and reduce inrush.


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## Jhellwig (Jun 18, 2014)

JRaef said:


> 200V is the designated "Ultilzation Voltage" (meaning motor design voltage) for a 208V Distribution Voltage as delineated in ANSI and NEMA standards. Just as 230V, 460V and 575V are the motor design voltages for 240, 480 and 600V Distribution Voltages. But in 10HP and below, most motor mfrs use a compromised design that allows their 230V motors to be used at 208V. But when someone buys a motor designed as 200V you can't use that on 240V systems. That's usually only done by equipment OEMs who want you to buy a different motor from their service dept if you move so they can charge you for it.


I have seen some labeled compressor duty and the specs on them look like they are putting just enough motor to run the load since it is intermittent. Luckily most can be fitted with a normal motor.


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## Forge Boyz (Nov 7, 2014)

Jhellwig said:


> I have seen some labeled compressor duty and the specs on them look like they are putting just enough motor to run the load since it is intermittent. Luckily most can be fitted with a normal motor.


That's where some weird motor sizes come from. I have seen a number of single phase 6.5 hp on upright air compressors. I know of one that is in a chemical company that runs all the time and is shot! They do have 3ph there but for some reason they have a cheap single phase compressor.


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## JRaef (Mar 23, 2009)

Compressor and power tool marketing is an art form of sorts. "HP" to them means next to nothing official or scientific. What they do is look at the PEAK torque of a motor at the SPEED that will happen at to come up with a "HP" value they can claim on the advertising piece, usually preceded by the word "develops", as in "New! Improved! Develops 6.5HP!"

So here's how that works. If you take a 2 pole 3600RPM motor that is rated for 3HP _continuous _at slip speed (3550RPM) and look at the PEAK torque it can develop (Break Down Torque) which is often at around 85% speed (3000RPM), the BDT might be as much as 250% of Full Load Torque for an INSTANT. The "marketing" HP calculation at that instant then is Tq x RPM/5250, so if the Tq as 3HP was 4.437 lb. ft., then 250% of that is 11.1 lb.-ft., so HP = 11.1 x 3000/5250 = 6.34HP. Fudge and round a few of those values and you can goose it to look like it "develops 6.5HP".


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## telsa (May 22, 2015)

I'd swap out the motor.

Ebay has NO END of decent units priced in the cellar.

Brand New:
*7.5 hp electric motor 213t 3 phase 1800 rpm severe duty enclosed free shipping*

$ 379.05



Typical offering.


BTW, there is some saving by going to a slower RPM at the compressor. (< friction)

For a dealer, why is he messing around with a miss-matched motor ?


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## RTW (Jul 9, 2016)

I'm working for a company that just bought a huge press from England and there voltage is 415v, they have 480v here in the U.S., i would assume that it will not work without installing a step down transformer. Just looking for some suggestions on what to do.


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## Handasee (Dec 18, 2009)

415v at 50 or 60 Hz?


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## RTW (Jul 9, 2016)

They said at 60 but it seems to they did not change anything


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## John Valdes (May 17, 2007)

RTW said:


> They said at 60 but it seems to they did not change anything


You can install a VFD and program voltage and hertz. :thumbsup:


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## Jhellwig (Jun 18, 2014)

RTW said:


> They said at 60 but it seems to they did not change anything


If it does say it can be used on 60hz it should have an amp rating at 480 volts as well as the motor speed at 60hz. If it only has a 50hz rating you will have to give it a 50hz supply.


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## John Valdes (May 17, 2007)

Jhellwig said:


> If it does say it can be used on 60hz it should have an amp rating at 480 volts as well as the motor speed at 60hz. If it only has a 50hz rating you will have to give it a 50hz supply.


Not necessarily. He can run a 50Hz motor on 60Hz.
You may remember a post I made a couple times. Last week actually I think was the most recent.
I had a customer call me and ask if he could run a Chinese 50Hz motor in his plant. Their nominal voltage was 230/480/60Hz.
I told him I could sell him a new motor at the correct Hz, but since he was a good customer, I told him to run it. Run it until it quit.
He would call or email me for several years after I told him that to brag that it was still running and has had no issues.

But you are absolutely correct. If its rated for 60 Hz it should have a voltage rating of 230/460.
He was told the same thing I told my customer. Run that MoFo until it quits.
He could use a VFD if he anal about following rules. Or speed is critical.


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## Jhellwig (Jun 18, 2014)

I was always told if it is only rated for 50hz don't run it at 60hz. I have never run into a 50 only piece of equipment.


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## John Valdes (May 17, 2007)

Jhellwig said:


> I was always told if it is only rated for 50hz don't run it at 60hz. I have never run into a 50 only piece of equipment.


Lots of times equipment comes in from overseas at 50Hz.
You have two choices.
Replace it with 60 Hz
Run it until it dies.

My customer ran it and i assume its still running.


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## JRaef (Mar 23, 2009)

What matters first is that the motor is getting the correct "V/Hz ratio", so for example a 460V 60Hz motor is designed to work on a V/Hz ratio of 460 divided by 60, so 7.67 V/Hz. As long as what you feed to it is within 10% of that, the motor is going to produce full torque, which MOST of the time is all that matters. So if you have a motor designed as 415V 50hz, the ratio is 8.3V/Hz, which is within that 10% window. It will be fine, and by the way, this is no accident. Motor mfrs want to sell their stuff to the widest market.

The thing that WILL be different is the speed of course. The motors will run 20% faster on 60Hz. That can be a problem, but without knowing the nature of the machine, it's hard to tell. If however the motor is on a CENTRIFUGAL pump, it can be a BIG problem, so be careful.


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## RTW (Jul 9, 2016)

There are hydralic pumps on this machine , of course the other issue is also that the control wiring is 240 volt which in england I think that's one wire to ground , the U.S. Is different of course may be better to just get a transformer for the whole machine.The machine is a 200 ton press. And I thank all that giving me input in this matter.


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## John Valdes (May 17, 2007)

RTW said:


> There are hydralic pumps on this machine , of course the other issue is also that the control wiring is 240 volt which in england I think that's one wire to ground , the U.S. Is different of course may be better to just get a transformer for the whole machine.The machine is a 200 ton press. And I thank all that giving me input in this matter.


How big is the motor? If applicable install a VFD for the motor only. 
A transformer cannot change the Hz. It can only change the voltage.
240 is available here and you have it in your plant right?

240 is 240. No matter if you read it ground, or across line to line. 230 is 230.
If you only have this one motor, get a VFD. 
Did I ask or did you tell us how big this motor is?


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