440V-460V-480V??? What gives??
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  1. #1
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    Why is some of my equipment rated for 440 volts while others are rated for 460 volts and still others rated for 480 volts three phase? My service is 277/480VAC but the power coming in is actually 500 volts!!!

    Why is there such a disparity in the voltage ratings on different equipment? Same with 220/230/240VAC and 110/115/120VAC single phase. Why the different ratings?

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    I think the answer is a compilation of alot of things. One is that standards have changed through the years. I think the 220v/440v is an old standard. 3300 sounds familiar and 5000 was an old voltage. Now 4160 is popular.
    110 through 120 is the same in my book. Your 480v service is 500v because of variances in the grid, your trans, time of day, etc, etc. It shouldnt be a problem. It certainly shouldnt cook any coils IMHO. My wall outlet is 124 right now, but it swings higher at times.

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    My service is 277/480VAC but the power coming in is actually 500 volts!!!
    Hi Rick,

    The service voltage at the breaker box will be nominal when the service is loaded to its rated capacity. If lightly loaded, the voltage will be higher due to reduced losses in the transmission system between the power company transformer and the breaker box.

    And your discrepancy is only ~4%. I believe service voltage varies over a range of ±5% to ±10%. I haven't looked at the specs recently. Maybe Peter knows.

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    "One is that standards have changed through the years. I think the 220v/440v is an old standard. 3300 sounds familiar and 5000 was an old voltage. Now 4160 is popular."

    4160 is a Y system, and Y has been out of favor for decades.

    A the municipal electric utility where I was an EE over three decades ago, we supplied customers with 120/240 single-phase (implicitly ∆), 240 three-phase (also implicitly ∆), 480 three-phase (also implicitly ∆), 120/208 three-phase (implicitly Y), 277/480 three-phase (also implicitly Y), 4800 three-phase (implicitly ∆) or 34500 three-phase (also implicitly ∆), at the customer's option.

    If the customer wanted 4160, or any other nonstandard voltage, then he had to supply a vault and a transformer made to our specifications, and we would install the primary side, but not the secondary side.

    110/115/120 are the same, just as 220/230/240 are the same, and 440/460/480 are the same.

    Insulation is 300 volts and under, and 600 volts and under, for conductors and also for cords. (Exception for "zip" cords, which is 150).

    575, as used in Canada, would be considered 600 volt class.

    277, as used in the US, would be considered 300 volt class, even though it is a component of the 277/480 Y system.

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    In the late eighties I worked for several companies in the S.E. and seemed like 440v was the communicated voltage. Common to see stickers on MCCs with that voltage listed. Now its 480v I see listed. Same voltage apparently as Peter points out, just described differently over time or over miles, or maybe both.

    I found that later customer (USS) had the 4160v, since I hadn't seen it, thought it was a newer thing, but maybe just to me. Its still alive and well there by the way. Once you invest in a voltage, kinda hard to change I suspect.

    Just did a little research and sure enough the old motor standard was 220/440v. Newer T frame motors have a 230/460v rating. So as far as motors go 220/440v was the old standard and higher voltages now the standard.

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    Y is occasionally found where a utility is short of funds, and yet needs to increase its capacity.

    A ∆ line will be "Y-ed up" to a higher voltage, but the line-to-ground voltage remains the same, so the conductors and insulators may remain the same.

    Yes, a neutral will have to be added, and this is usually added between two of the phase conductors, and placed on a very short insulator.

    When you have a Y transmission or subtransmission line, you implicitly lose the ability to supply three-phase power in the presence of a temporary phase-to-ground fault, plus your protective relay scheme is more complicated as "zero sequence" currents flow in a Y system, whereas these cannot flow in a ∆ system.

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    Semantics.
    There are 2 "voltages" to be concerned with. One is the "Distribution Voltage", meaning what the utility gives out; the other is the "Utilization Voltage" which is what the device or motor is designed to use. Because the US power "grid" as we know it now was originally a big bunch of unconnected separate producers, each producer had their own standards. Large ones early on such as New York, Chicago, Boston etc., were where the biggest market for electrical products were, so manufacturers tended to cater to them and their standards. This ultimately had the effect of driving other smaller utilities into conformance because their users sometimes found it difficult to find appliances and machinery that would work at odd voltages. 460 was chosen by NEMA (National Electrical Manufacturers Assoc.) as the compromise utilization Voltage because it was mid way between 440 and 480, and they also specify that motor HP and torque ratings would be based on a +-10% voltage level from there. So a 460V rated motor can tolerate any voltage from 414 to 506V. The same is true for 230V as the compromised Utilization Voltage, because motors can then tolerate from 207 to 253V, although most new motors are designed now to accept from 200-250V because of 208V systems. 115V is the compromise between 110 and 120V, although at that level you still see ratings all over the map because it really doesn't matter.

    If you pay attention, you won't see motors with nameplates that say 480V (unless they were specially wound for someone). You will however see VFDs that say 480V, because they are referring to the VFD's voltage tolerance, not the motor you connect to it. In a VFD, the output voltage can be lower than the input voltage, so you tell the VFD what the motor nameplate says anyway.

    If you have a 3 phase motor that says 440V or 220V on the nameplate, it was designed specifically for that voltage, which means it is pre-NEMA. That also means you don't necessarily know the voltage tolerance if it's not stamped on the nameplate, so be careful.

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    Jraef;
    You "hit it on the nail".
    Jamie

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    To say it another way: Previously motors were built to best operate at 440v. They were tuned if you will to be most efficient at this voltage. Nema standard comes along and with it T frame motors and target voltage is increased to 460v "as a compromise". The voltage was changed with this standard. No big deal, but I don't see "Semantics" there because these are two different build to voltages.

    I have a 200v motor that runs great on 240v by the way.

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    Want to bump this thread instead of making a new one. I got about 5-6 different pieces of equip/machinery in my shop that are all a bit older. One radial drill being from the 40s.
    Pretty sure all the stuff i have is driven by dual voltage 220v /440v motors.

    Just measured my shop votage at a couple outlets and im at 500-510v!!!
    One meter read 500v average and the other meter read 509 average.

    Am i going to damage these elecric motors? That would be really expensive and bad!
    So do i not worry about it?

    Or install some sort of step down voltage transformer?

    As for motor starters, if 440/460/480 is the same thing then why are there so many different coils avail with different voltages like 440v and 480v? Im looking at buying a allen bradley 709 starter on ebay right now and the coil is rated at 480v. I was originally looking for a starter that had a 440v coil....

    What gives?

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    There is one thing that I would do before I would spend any money on anything and that is to check your voltmeter. I worked for utilities for over 40 years and I seldom ran into a problem with high voltage. In almost all high voltage complaints it was the customers meter that was the problem. Call your utility and ask them to come and check your voltage.

    Here is a link to ANSI C84.1 that gives the specs for service and utilization voltage.
    ANSI C84.1 ELECTRIC POWER SYSTEMS AND EQUIPMENT - VOLTAGE RANGES |
    Power Quality In Electrical Systems


    As far as the 440/480V issue it is all the same voltage, on UL/CSA equipment there is a minimum 10% tolerance. Different countries/utilities will have a set standard. The utilities I worked for called it 277/480V

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    I checked with a analog meter and a digital meter. Possibly their both off but id doubt it.
    So a allen bradley 480v coil is basically the same as a allen bradley 440v coil? Interesting they made both as different part numbers.

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    Remember the voltages listed are True RMS voltage. Quite often many meters will not read the True RMS voltage. The peak voltage is much higher than the RMS voltage so that is where the error occurs.

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    Running a 480v motor on a 500v system PROBABLY won't cause it any problems.

    I'd be more concerned with imbalance between the 3 legs. Are you getting similar voltages when you measure A-B, B-C and C-A? Also, are the amperages similar on each leg? If the voltage is different on one leg, that could cause the amps to change also. If the voltages are all similar and the amps are different that could be a problem in the motor.

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    Starter coils are different from motors. Motors have magnet wire insulation that is designed for higher temperatures, because the amount of heat created in the motor is related to the amount of work it is doing., so the insulation must cover the "worst case scenario". Not so with a contactor coil, it does the same work regardless of what is going on in the motor, it's just making magnetic fields to pull thew contactor armature in. So if you give too much voltage to a coil in a contactor, the excess magnetic flux is just going to turn into heat, and heat x time = failure. That's why the mfrs sell different voltage ratings, or at least used to. The A-B 709 series starters went out of production in about 1979. back then the coil technology was less exacting, so more exact coil voltages were important. Their 509 series starters, which are now themselves going obsolete, had a wider voltage tolerance because the new coils were made better. The 309 Series that is replacing it now has "universal" coils, meaning you have one coil that is good for 100 - 250V and another that is 250-500V, AC or DC all in the same coil.

    As mentioned earlier, the older numbers (220/440) predate the "T frame" motor redesigns that took place starting in 1964. the "U Frame" came from 1952 and prior to that there was what is referred to as the "original" standard. Beginning with the U frame motors, the insulation of the motor windings became what we now call "Class A", meaning 105C max, prior to that there were few insulation temperature standards, hence the move to standardize after WWII. Then starting with the T frames, that was upped to Class B, 130C and we now have upward of Class H which is 220C rated. If you have motors made before even the Class A winding rating, it will not be very tolerant of temperature as modern motors are. Yes, there is more iron in them so they tend to look beefier, but the winding insulation was not as good. If they have been re-wound over the decades, they may have better insulation now, but do you know? Probably not. So bottom line, giving a 440V rated motor +13% to +16% voltage is likely to hasten its demise.

    Take a look at this chart on the effects of voltage variation on AC induction motors. You'll see that at +15%, the FLA goes up and the efficiency goes down, BOTH of which will increase the motor temperature.

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    Default My experience with motors and voltages

    Quote Originally Posted by Rick Rowlands View Post
    Why is some of my equipment rated for 440 volts while others are rated for 460 volts and still others rated for 480 volts three phase? My service is 277/480VAC but the power coming in is actually 500 volts!!!

    Why is there such a disparity in the voltage ratings on different equipment? Same with 220/230/240VAC and 110/115/120VAC single phase. Why the different ratings?
    In my experience voltages have risen over the decades because there has been more demand, which lowers the voltage on the transmission lines and from the transformers, I remember 208v Motors being the norm, then it went to 210, then 220, then 240.

    It comes down to money, doesn't everything?, specifically cutting power loss where the utility companies are concerned, transmission and transformer (loss of electricity) is lower at higher voltages. So in short, transmitting electricity at higher voltages, saves the Utility companies money.

    Most industrial 3 phase motors are internally wired for the higher voltage range 440,460,480, they are usually more efficient at higher voltages than when wired in the 208, 210 220, 240v low range.

    Higher voltage windings are heavier and provide more inductive power so they are less likely to lag with increased load, increased load raises current flow as voltage drops.
    As voltage drops and current increases more energy is turning to heat in the windings instead of inductive magnetic power to the shaft.

    I have 247 volts at my outlet right now, but I would have no problem running a 208v motor with this over 18% increase in voltage. I will be drawing less amperage at 247v which equals to transmitting less heat into the windings.

    I have a Cincinnati Mill it is rated at 480v, I would want to consider heat if running a lower voltage to it like 440 because if I load the machine down it is more likely to lag and trip the overload drawing higher amps through the heaters in the overload.

    Everything in life is relative, you can have 2 cars each towing a trailer one has a larger motor, as they both go down a level road both have no problem with horsepower to do the job but when they come to a hill the car with the smaller motor will have to work harder to keep up, which will generate more heat and more drag or lag on the motor and it might overheat. Loading an electric motor down with a lower voltage power applied increases the heat in the motor windings breaking down the insulation which over time if it continues will destroy the motor

    Like with welders, comparing them to motors, some are heavy duty, they use more copper in the windings to make them stronger, in a welder it is called duty cycle, that is how long you can continuously weld without overheating the windings. A heavy duty motor will have more tolerance to overheating as voltage drops but it is still a concern when you are loading it down.

    I have yet to see a motor burn up with a higher voltage within the high voltage range 440, 460, or 480, it is lower voltage than what is rated that can destroy them. When you slow the shaft down with load and the voltage is lower, the motor has less power to keep up with the RPM the frequency wants the motor to turn, when this occurs more heat is generated in the windings and less into magnetic power in the windings.

    I can probably easily run my Cincinnati 480V mill at 440 or 460volts, but I would have to watch the load I was putting on the machine, because the heat and amperage draw will increase at lower voltages.
    Motor lag, which is the amperage leading the voltage increases with load, this increases motor winding heat, just like a motor in an underpowered car pulling a trailer up a hill.

    If you want to get technical and you are into math, read this link and it explains things relative to motors and electricity, it gets very complicated more than I have time to study.

    Motors are usually protected from heat, but if they overheat once you better find the problem.... because each time they overheat, the insulation in the windings breaks down and the more it breaks down, the more electricity flowing into the motor turns to heat instead of power to the shaft, it will eventually come to a point where it loses all power and will not start and instead just create heat or burn up.

    The break down of the motor winding insulation allows electricity to flow across the windings instead of through the wire of the winding which decreases the induction of the magnetic field that gives the motor it's power to start and run, if it does not start it has 100% lag and becomes a heater burning up or tripping out the overload.

    The link below gets into detail more than I care to know, common sense and experience sometimes is better than book smart.

    https://www.me.ua.edu/me416/LECTURE%...fic&PF-CM5.pdf

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    Just time and the cost of distribution higher the voltage the lower the amps, so less loss...In 1909 the standard was 100, 200, and 400 volts and 208, and 277 were not used...simple...Phil


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