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View Full Version : Electrical Power; So many voltages - can you set me straight?



Mcgyver
04-04-2009, 10:56 AM
I'm wading into industrial power in that its time to replace the static phase converter with a rotary, so I'm looking for a motor. So I'm thinking about voltages and such, and am a bit confounded in that there are so many different nominal voltages, what it means, and whether its important.

For example, we have line voltage in Canada of 110, or is it 120? I hear both referred to. this line link says its 120 (http://www.kropla.com/electric2.htm) for Canada. With two lines everyone calls it 220, well if each leg is 120V, why isn't 240? yet its commonly referred to as 220V

Then i find a motor that is 208/416. now 400 something sounds US, but why the 208 instead of 220 or 240? is a 208V motor going to work well for my 220V converter?

600V is the most common industrial service in Canada, or at least Ontario where i'm familiar with it....but you hear machinery stated as being 575V? what the heck do they plug it into? why 575 and not 600? Then there's transformers; l've found 600/240, 600/230, 600/220 600/208 etc etc....why such variety; aren't you wanting to step down to a standard say 220?

I understand there's some variance, but if the nominal service is supposed to be say 220, why do what devices that are 208, 230, 240, etc? in a practical sense, are 208, 220, 230 and 240 all considered to be about the same thing in they line supplies not regulated power supplies?

figured this was the place to get straightened out on all this, thanks :confused: :D

J Tiers
04-04-2009, 11:07 AM
208 line-to-line 3 phase is 120V to neutral........

110 is obsolete... it is generally 120V +- 10%, although that may vary during the day. That does make 240V. 220V goes with 110v... obsolete.

Mcgyver
04-04-2009, 11:13 AM
well that was easy :)

so a 208V 3ph motor is exactly what i want? (in the context of a rotary phase converter with 240 going into it)

SGW
04-04-2009, 11:18 AM
Good questions. I'm sure there are experts here who can enlighten us.

My understanding (subject to confirmation by somebody with more confidence than I have) is that 120 is the old 110. Originally, house voltage was 110, but it's been creeping up over the years because higher voltage makes for more efficient power transmission. By the 1960s it was around 115V. Now it's nominally 120, but every time I measure my line voltage it's actually around 124.

I think the 220/240 ambiguity is the same thing. It began as 220 (2 x 110) but now is more correctly called 240.

The 208/240 business is something else again. It depends on whether the supply transformer is Wye or Delta. Wye gives 208, delta gives 240 (I think). I profess nearly total ignorance as to the implications of that, as far as hooking up a motor is concerned.

...but all that may be incorrect....

Duffy
04-04-2009, 11:40 AM
Mcgyver, call Toronto Hydro and ask them. As for all the variations, one explanation is that a lot of stuff we run in Canada is imported and it was often cheaper to install a matching transformer than change a motor. Here in Ottawa, there are Federal buildings, ( laboratories,) with 575 volt 3 phase fans everywhere. These were build in the 50s and 60s. The later stuff was 600 volt. And because someone was frightened of "high voltages" there were main building fans of 500 HP at that voltage. The buss systems are truly awesome, and silver plated copper in many cases! Ah taxpayers money at work! I think that the voltages above 2-something are largely determined by the high voltage feeds. For example, here in Quebec, our residential single phase feed is 14400 volt, which is, I think, 25000 line-to-line 3 phase. While across the river, the older sections of Ottawa are some lower voltage and in the newer sections, it is 44000 3-phase. Electrical infrastructure has a LONG life. I had a tour of a little hydro plant, (about 5 mgawatts,) owned by Ottawa Hydro. It was installed in 1905-how could I tell? that was the date cast into the oil-filled transformer housing! I know, this only adds to your confusion, but I am guessing that you will end up with either 2something 3 phase or 4something 3 phase-whichever has the greatest selection of cheap motors.

loose nut
04-04-2009, 11:51 AM
It's a case of new standards like 120/240 haven't been adopted because the old equipment is still good. When a system is upgraded it is brought to the new standard but that can take a while. I believe that there are still some places in NA that still use the 117 volt supply that was common a long time ago. Just because something is obsolete doesn't mean it will be replaced.

JoeFin
04-04-2009, 12:27 PM
You guys need to understand Power fluctuates – it’s not a constant

When you monitor power you’ll commonly see fluctuations in voltage and hertz. Additionally as the voltage travels down the line sets or wires in this case conditions of voltage drop, capacitive reactance, inductive reactance and impedance all exist and have their effect on the final outcome of the power produced

Additionally what is the meter movement resistance of the meter you are using to measure the voltage and or Hz? That will have an effect also on your measurements.

So we have this thing called “Nominal Voltage”

In the case of 120 volt it would be a range from 110v to 120v. If you read more then that with your meter your meter might be out of calibration or the taps on the transformer supplying the voltage are set high to compensate for voltage drop some where on the system the transformer supplies – but the objective of the Taps on the Transformer were to achieve a voltage in between 110v and 120v at the outlet.

So what ever voltage the industry is currently referring to in their literature they are talking about nominal voltages.

Read the specifications of the equipment. More often then not they refer to a “Voltage Range” – Why you ask? - Because Voltage is not a constant

Paul Alciatore
04-04-2009, 12:54 PM
110, 115, 117, 120, or whatever. Please notice that there is a +/- spec associated with all of these values. For example, +/- 10 % of these values is plus or minus 11 or 12 Volts. So 110 + 11 is 121 or 120 - 12 is 108.

If you put a Voltage monitor on the power lines in any area and record the Voltage for a day or week, you will probably see all of the above numbers and even more. It is not unusual for the Voltage to drop down into the 90 on a hot summer day. I worked at a TV transmitter site in New Orleans some years ago and there was an aluminum plant nearby. Some nights the line Voltage would go so low that my monitors would not even work and I had to call the studio to check and be sure we were even on the air. One time we were down in the 70s.

My point is, that there is a large variation in the Voltage of the power distributed. The people who make electric and electronic equipment that is designed to work from commercial power are aware of this and most such items are capable of proper operation over an even wider range of Voltages; 95 to 130 is not unusual.

When different people talk about the Voltage, they tend to use different numbers for whatever reason. But generally speaking you can assume that any number from 110 to 125 is more or less talking about the same thing and can be used interchangeably. This is the most common nominal Voltage used in the US and Canada.

The various nominal Voltages are related by ratios that are determined by the physical properties of the generation and distribution system. Some of these are locked together by definition, like 220 is actually exactly twice the 110 figure. So if the 110 is actually 115, then the 220 is actually 230. Thus we get a simalar range for 220 from 220 to 250. These Voltages are functually the same in exactly the same manner as the 110 to 125 range.

Other nominal Voltages are also related to these, thus 208 is derived by two 110 Volt legs that are 120 degrees apart. This invloves trig. But it will give you a similar range.

Another example; I have a mill-drill at work that has a motor that is nominally rated at 220 Volts. But building power is three phase so a nominal 220 is not available so we are using 208. It works just fine.

Mosside
04-04-2009, 12:59 PM
I understand there's some variance, but if the nominal service is supposed to be say 220, why do what devices that are 208, 230, 240, etc? in a practical sense, are 208, 220, 230 and 240 all considered to be about the same thing in they line supplies not regulated power supplies?

figured this was the place to get straightened out on all this, thanks :confused: :D

When choosing a motor, whether the plate says 208, 220, 230 or 240 they will all work fine on a supply voltage of say 230 volts. You have a wiggle room of +-10%. I have a motor that is 240 volts but it says that it is rated for 208 service. What that means is that it can handle the extra heat that may be produced from the higher amperage that will be drawn from the lower voltage service.

On three phase 208 is a little different and though I have had it explained I forget exactly. On normal 3~ each line will be 230 (give or take) to each other but two will be 120 volts to neutral and one will be 240 volts. On 208 I think all are the same to neutral. "I think" it is easier to get single phase service out of a 208 system.

I would like to say however that if you are getting into transformers to get you to 600 volts for that new mill please note that this is NOT THE PLACE TO PLAY ELECTRICIAN. I am fortunate to have a buddy that is an electrian to help me build my RPC and install my transformer. I was impressed with how much care and respect he had for that higher voltage. IT DOES NOT ALLOW FOR MISTAKES, IT WILL KILL.

Doug

Mcgyver
04-04-2009, 02:21 PM
110, 115, 117, 120, or whatever. Please notice that there is a +/- spec associated with all of these values. For example, +/- 10 % of these values is plus or minus 11 or 12 Volts. So 110 + 11 is 121 or 120 - 12 is 108.

.

I get that there is variance, but like turning part to a nominal 1" with a +-0 .001 tolerance, you'd sell your part as a 1" part, right, not a .999 part. So if the nominal is 120V, it would seem logical that maker would call it 120V. From the posts it seems more a historic change as voltages have crept that have led to the differences; what was once made to 110 is now 120 while either will currently work.

Doug, thanks for the reminder. The concern is not without merit, I have little experience with 3 phase equipment or 600V. The flip side is i will not go ahead until i do know enough to be safe...and will most probably get someone who knows to check it before turning it on. otoh 220 will also kill and i'm not been intimidate by it ( i do understand why 600 is that much more deadly), I just don't act until I'm sure....not the arena to fire something up to see what happens. I am of course open to specific ideas and notes on how to remain alive :)

hardtail
04-04-2009, 02:42 PM
You will find single phase residential service to be 115/230V in Canada.

Compatible voltages are generally considered within 10% of supplied service so 208 is on the edge of acceptable for 230V service, 208 is normally a 3 phase industrial voltage but it will work.

550,575,600 are of the same voltage class as 550 to 600 is on the edge of the 10% deviation allowable. Generally you will find most industrial machines in Canada at 575V.

So for your choices on transformers the 600/230 would be the best. Transformers usually have multiple taps that will let you fine tune your system through hookup.

Test a plug in with a meter to be sure........600V does have more pressure and is not something to fool with but it also carries far less amps so for the same load so it's not something to be terrified of either, you should have a good working knowledge to work with anything over 24V AC, now 24V DC that can bite.........LOL If you are comfortable with 115/230 and 3 phase power, 600V is just as basic.

doctor demo
04-04-2009, 03:01 PM
I would like to say however that if you are getting into transformers to get you to 600 volts for that new mill please note that this is NOT THE PLACE TO PLAY ELECTRICIAN. I am fortunate to have a buddy that is an electrian to help me build my RPC and install my transformer. I was impressed with how much care and respect he had for that higher voltage. IT DOES NOT ALLOW FOR MISTAKES, IT WILL KILL.

Doug


Doug, I'm not an electrician by trade... but I do a quite a lot of electrical retro fit for machine install/moves.

A lot of people feel the same way that You do , as far as the respect for the higher voltages. Don't be fooled, 120 volt can and will Kill You if not handled with the same respect and care as the 600 volt circuts.

In fact I have heard from more than one source that more people are killed by low voltage home type stuff than the higher volt applications.


Steve

J Tiers
04-04-2009, 03:42 PM
The variation in voltage is a given....... Often it is lower in daytime, and higher after 4 PM, as factories stop for the day. We had 118 daytime, and 125 after work at our old place. Dunno what it was at midnight, wasn't there......

The FREQUENCY does not vary much at all... it can't or the grid would be erratic..... huge power direction shifts occur for very minor changes in phase, let alone frequency.

The 120 vs 480 isn't the voltage only, it's the energy. The welding arc that occurs with certain faults can fry you with radiated heat/UV at 480+ where it would only surprise you at 120V.

Mosside
04-04-2009, 03:57 PM
Doug, I'm not an electrician by trade... but I do a quite a lot of electrical retro fit for machine install/moves.

A lot of people feel the same way that You do , as far as the respect for the higher voltages. Don't be fooled, 120 volt can and will Kill You if not handled with the same respect and care as the 600 volt circuts.

In fact I have heard from more than one source that more people are killed by low voltage home type stuff than the higher volt applications.


Steve


I do most of my own electrical work for my business myself and maybe I'm not as nervous of the dangers as I should be with the lower voltage.

I wonder though if the reason more people are killed by the lower voltage is that people do themselves and don't take the precautions.

The one thing to note is that you do need wire that is rated for 600 volt. Most of the wire sold at the hardware store will not do it.

The other thing I wonder about but have never asked is if having 600 volt power puts us in violation of our home owner insurance policy.

Doug

hardtail
04-04-2009, 03:59 PM
Doug, I'm not an electrician by trade... but I do a quite a lot of electrical retro fit for machine install/moves.

In fact I have heard from more than one source that more people are killed by low voltage home type stuff than the higher volt applications.

Steve

Here lies the truth, possibly because it is so much more widespread extending into all homes of the civilzed world?????

Any electrical supply or device should be respected irregardless. My buddys brother played hockey with a commercial electrician on his team, his basement got flooded in a summer storm, he went down after all the water had drained and it was damp and plugged in his Shopvac and then at that instant left this world........

I am not an electrician but have worked in industry for 20+ yrs where we take it in at 14.4KV and start knocking it down for our needs, McGyvers transformer is surely been designed as a stepdown but will do the same in reverse. I only got bit once in this time by 600V and it's not something you ever want to repeat, after a few minutes the dots in my vision started going away.........a lucky reminder.

McGyver it's too bad your not closer as I have a number of 1750rpm 575V motors that would be suitable and best of all free (grin) for your RPC, you'll have to size your RPC about 40% larger for your idler than your total load.

Mcgyver
04-04-2009, 08:56 PM
geez, you're killing me...if you feel like a drive I'll buy the first round :D

hardtail
04-04-2009, 11:05 PM
I'm coming out in the fall to visit my sister and friends to see the beautiful colours and sights once again but I have a feeling that will be too long for Elliott to wait and the idler will grossly exceed my carryon allowance.......LOL

I'm just putting together my RPC right now, I'm not going with start and run caps just yet so it's rather simplified, I could post a pic as I built a cart for it which might qualify as something under the welding category......LOL Keeping your control circuits off the generated leg is all the advice one needs.

It's amazing how many electricians don't know about phase converters, maybe one of the best kept secrets for a homeshop guy bidding in industrial auctions??????

I'm heading Torkers way in a month and thought he might need an idler for Mr Norman but he likely has other things on his mind at the moment.......starting to sound like the deliver an idler Canada tour this summer.......LOL

vincemulhollon
04-06-2009, 01:33 PM
I would like to say however that if you are getting into transformers to get you to 600 volts for that new mill please note that this is NOT THE PLACE TO PLAY ELECTRICIAN.

Folks on this board may not realize that most electricians have a vast collection of extremely long (18+ inch) and extremely expensive drill bits that always seem to require sharpening, or are somewhat bent. Also most electricians have some gadget or another that a machinist could help them fix, maybe drill chucks that are "gritty" or loose or wobbly, or that extensible fiberglass thing they use to pull cables that doesn't lock up correctly.

If you can sharpen drill bits better than he can, and he can check your plans and wiring better that you can, no money need change hands and both go away happy. Or worst case some beer changes hands to even it up.

Its not just safer, its also more efficient to trade.

camdigger
04-06-2009, 06:02 PM
Several of the commercial electricians I know need to have the burnt ends of their screwdivers sharpened too.:rolleyes:

keelan
04-07-2009, 02:14 AM
The FREQUENCY does not vary much at all... it can't or the grid would be erratic..... huge power direction shifts occur for very minor changes in phase, let alone frequency.

I know that the alarm systems on the big UPSes I monitor at work have never triggered on input frequency variations. It's always a rock-solid 60.0 Hz.

I remember reading in a book from 1929 that the goal of electrical companies was to keep the number of cycles in a 24 hour period the same (5,184,000 cycles total for 60 Hz). This meant running the generators a little faster or slower at night to make up for cycles lost during the day -- a clock with a synchronous motor will never cumulatively gain seconds day-after-day. This was back in the days of manual controls (master clocks, ingenious electromechanical solutions, etc.), so things will have only improved since then.

Rob Peterson
04-07-2009, 02:27 PM
IEC 60 038 lists standard supply voltages for three phase 60 Hz as 600V, 600/347V, 480V, 480/277V, 240V, and 208V/120V. Single phase 240V/ 120V are sort of a subset of 240V. Note that 230V, 220V, 115V and 110V are not in that list. There is a diagram at www.crmagnetics.com/std_vola.pdf (http://www.crmagnetics.com/std_vola.pdf) that shows how the various voltages are related. I think 600V based systems are pretty rare in the US, but they are more common in Canada. There are parts of the 50 Hz world where 230V is a standard voltage, but it is definitely not in Canada or USA. As others have pointed out, the actual voltage at your house or shop is only going to be close and probably low.

So if there are only a couple meaningful supply voltages, why are there so many different voltages on nameplates?

For most industrial motors, the voltage on the nameplate is not the supply voltage that the motor is expected to be connected to. The motor’s nameplate is telling you the (minimum) voltage and current at which it was designed to meet its rated horsepower. Industrial users want to know that when they pay for 50 hp, that they will get all 50 hp in their real world situation of voltage drops and overheating. So the motor manufacturers have to rate their motors power based on a voltage reasonably below the supply voltage. Common numbers are 575V for 600V supply, 460 for 480, 230 or 220 for 240, 110 or 115 for 120, etc. It is a way to ensure real world performance and avoid misleading power claims.

Motors are special this way; other devices are rated differently. Check the back of your coffee maker - it will be rated for 120V, not 110V. In this case, it is saying that it won't burn up if you plug it into a supply voltage of 120V.

SDL
04-07-2009, 02:43 PM
230V is the nominal Phase to Neutral in Europe where mainland Europe was on 220V 50Hz and UK was 240 V 50Hz.

One of the things to watch for with 600V is that a lot of control gear Breakers and Contactors are not rated that high. No doubt they will have the correct gear in Canada but some equipment originally destined for USA may not have correct control gear.

We often run into this problem at work even though we build UL lised equipment for USA no good for Canada.

Steve Larner

darryl
04-07-2009, 09:24 PM
Can't add much to what's already been said, but interesting anyway- when I worked in Africa, the voltage could actually fluctuate up to 270 volts, and down to 150 volts. There were regulator boxes available (very high prices) for equipment that couldn't stand the input voltage swing. It wasn't usually that bad, but you could tell what time it was by the change in brightness of your lights. When an industrial load cut off you got a quick surge in brightness followed by continued higher-than-normal brightness level. It could get pretty low around dinner time, and we'd get a brightness peak early in the evening.

I worked in a factory making guitar and pa amps, and there was always a consideration of which transformer tap to wire up, depending on where the amp was going to be used. Testing the finished products (my area) had to take into account ac input voltage at the time of setting bias levels. We were looking to see 230 to 240 volts at this time.

There were quite a few large variacs in use in theatres, etc, where our band would play. Most were used for lighting, but some were used to plug the pa amps into. Some of the bands we worked with insisted on that, and some sound guy would be intent on checking the meter readings.