# 575 volt? Why is this not 600 volts?



## power

I own a southern Alberta (Canada) Electrical Company, and we commonly are directed to connect some American built equipment/machinery. While most commercial American equipment is 480vac 3-phase, some American manufacturers will custom build their equipment for our higher voltage applications here in Canada. In Canada, we have:

208Y/120v 3-phase 4-wire or 208v delta
480Y/277v 3-phase 4-wire or 480v delta
600Y/347v 3-phase 4-wire or 600v delta

Naturally, all the line voltages above are the product of the phase voltages x root 3 (1.732). This is a mathematical given, as the phase voltages are 120deg displaced from each other and are non-linear loads. 

For some reason, American and overseas manufacturers refer to the higher voltage as "575" volts. While our distribution transformers may permit us to tap them as low as 575 line voltage, we would NEVER do so. While a motor may operate on 575vac 3-phase ok, industry norm in Canada is to connect for 600vac line voltage, thus producing 347vac phase voltage. 

Does anyone know why the reference to "575"? (Maybe it's the same reason we have some people still referring to "460"...I don't know!!! :001_huh


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## Vintage Sounds

This post is pretty detailed


JRaef said:


> Nothing happens in isolation, it's a process of lots of small seemingly insignificant changes. I had to do a paper on this a long time ago, it has fascinated me ever since. Here's what I remember (may be some errors due to deceased brain cells now).
> 
> Edison chose 110VDC for lamps because he was matching the lumen output to compete with gas lamps, and through trial and error, he settled there.
> 
> Tesla and Westinghouse, in order to sell the world on AC, had to make it work on Edison's lamps, so they used 110VAC (lamps don't know the difference).
> 
> When larger motors were needed, they doubled the 110V to 220V because the transformer math was simpler that way.
> 
> When more power was needed with fewer wires, they went to 220V 2 phase by just adding transformers. Most of Tesla's first polyphase motors were 220V 2 phase.
> 
> By then the Europeans got into the AC game. Like Edison, Werner von Siemens had pushed DC on everyone. AEG, although a partner to Edison originally, competed fiercely with Siemens so they championed AC once they heard of Tesla's discoveries. AEG actually made the first 3 phase AC motors. They chose 50Hz (long complicated reasons), and 380V as a distribution system because they needed to move it 100+ miles in their first demonstration, and that proved to be the best voltage at the lowest cost.
> 
> When Edison and Westinghouse heard of it, they jumped on board. The first 3 phase generator in the US was built by GE (Edison) in Redlands, California for farmers, it was 2400V *50Hz *because the generator was made by AEG. Once that concept caught on, more people wanted 3 phase AC but Edison and Westinghouse were not yet making motors, so they were buying 380V 50Hz motors from AEG.
> 
> But by then they had already settled on 60Hz. So to make those motors work, they matched the V/Hz ratio of those motors so that there was no loss of torque. 380V 50Hz = a V/Hz ratio of 7.6, so to use those same motors here at 60Hz, 7.6 x 60 = 456, rounded up to 460V.
> 
> Some areas used 440V (so I'm told) because they already had 2:1 transformers for making 110V into 220V, so they just used those and ended up with 440V and it was within 10%, so close enough. Then when 220V became 240V, that became 480V.
> 
> I actually think that the 440V standard became 480V more directly on purpose. Officially, motors are NOT wound for 480V, to this day the NEMA design voltage for standard AC motors is 460V, also called the "Utilization Voltage" by IEEE. The DISTRIBUTION voltage is 480V, which allows for some voltage drop before it gets to the motor. So I think that the "lazy" approach to system design voltage that got us 440V became an issue for 460V motors when voltage drop was factored in, so they raised the standards to 480.


I have an old textbook that refers to the 600 system as "550 volt". I believe 575 is what motors are marked with as their "utilisation" voltage(after voltage drop, etc) even if 600 is theoretically what we supply them with.


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## backstay

power said:


> I own a southern Alberta (Canada) Electrical Company, and we commonly are directed to connect some American built equipment/machinery. While most commercial American equipment is 480vac 3-phase, some American manufacturers will custom build their equipment for our higher voltage applications here in Canada. In Canada, we have: 208Y/120v 3-phase 4-wire or 208v delta 480Y/277v 3-phase 4-wire or 480v delta 600Y/347v 3-phase 4-wire or 600v delta Naturally, all the line voltages above are the product of the phase voltages x root 3 (1.732). This is a mathematical given, as the phase voltages are 120deg displaced from each other and are non-linear loads. For some reason, American and overseas manufacturers refer to the higher voltage as "575" volts. While our distribution transformers may permit us to tap them as low as 575 line voltage, we would NEVER do so. While a motor may operate on 575vac 3-phase ok, industry norm in Canada is to connect for 600vac line voltage, thus producing 347vac phase voltage. Does anyone know why the reference to "575"? (Maybe it's the same reason we have some people still referring to "460"...I don't know!!! :001_huh


The paper mill I use to work in(USA) was 575 not 600.


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## Vintage Sounds

backstay said:


> The paper mill I use to work in(USA) was 575 not 600.


Is(was?) it easy to get motors in this voltage over there?


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## backstay

Vintage Sounds said:


> Is(was?) it easy to get motors in this voltage over there?


I think there were over 5000 motors in place and at least one spare for each. I didn't do the buying, but 575 motors didn't seem to be a hard thing to find. The "normal" voltage around my area is 480 volt 3 ph. Only the paper mill was 575.


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## CPSS

A bit of a late response, but we do a lot of railroad work, I always see equipment listed as "575V". Most of the commercial supply voltage is 480V, equipment seems to work fine all these years.


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## power

I did indeed observe your reply CPSS. I am assuming you are our American friends. We have an additional commercial voltage supply than the does the US. While America and Canada have 120/208 and 277/480, only Canada typically has 347/600. True, there are *some* areas of the US where 600volt equipment has been connected for manufacturing purposes, but generally, it's very rare.

It is unlikely that an American contractor would connect a 480vac supply to equipment marked with it's primary voltage as 575. Unless an American contractor purchased transformers from Canada (or custom wound xfmr from US), there is insufficient voltage in the US to power Canadian equipment. 

My original question was......why is the number "575" continually referred to by the equipment producers? It baffles me.....phase voltages displace their mating line voltages by a multiplier of root 3 (1.732). This is true for 120 to 208.......indeed it's difference with a multiplier of root 3. Same is true for 277 to 480. But.....somehow......equipment producers don't follow the same pattern for 347 to 600!!!! They keep referring to 575!!!!!! 

This just bugs me......no biggy.......I am not worried about it. I just thought if anybody knew the answer, I'd like to know it too.

Regards


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## Big John

_Vintage Jraef_ called it.

The number on the motor is the utilization voltage. It's deliberately lower than the system voltage in order to account for voltage drop within the building wiring.

That's the reason the name plates are often 200, 230, 460, 575 volts. Each one of those accounts for a 5% drop from the nominal voltage.

I never saw 600V down south, but I've run into a lot of it around New England, I assume it's a disease they caught from from the Canuks.


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## JW Splicer

I've never seen a 600v system, but I've heard some places (utilities?) use a 600v primary vs 4160v and step down to 480v at the customer.I thought it was wierd. I'll try to find the reference....


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## Nisat

I think the manufacture of the transformer , has to meet NEMA voltage drop requirement which range from % 6 to - %13


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## power

Thanks so much guys.....now I see why the difference between 575 and 600! Great! Thanks!


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## AR575

Oilfield uses 575volts on alot of the baldor reliance brand motors. The older equipment had 480volts but it's mostly becoming obsolete on oil drilling equipment.


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## brian john

power said:


> Naturally, all the line voltages above are the product of the phase voltages x root 3 (1.732). This is a mathematical given, as the phase voltages are 120deg displaced from each other and *are non-linear loads*.


What do you mean by this?


> Does anyone know why the reference to "575"? (Maybe it's the same reason we have some people still referring to "460"...I don't know!!! :001_huh


We have 465 in parts of Maryland and DC.


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## oldsparky52

Don't hold your breath waiting on an answer. Post was 8 years old and the poster hasn't been around for 5 months.


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## brian john

oldsparky52 said:


> Don't hold your breath waiting on an answer. Post was 8 years old and the poster hasn't been around for 5 months.


I never check dates and I end up posting to age-old threads quite often.


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## oldsparky52

brian john said:


> I never check dates and I end up posting to age-old threads quite often.


I think we all do/have.


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## micromind

And a lot of old threads are still relevant today. 

New members contribute and it can be a good discussion.


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