Results 1 to 20 of 20
Thread: 440 volt machine...why not 480 ?
09-02-2009, 06:24 AM #1
440 volt machine...why not 480 ?
Just bought a new German machine that is listed at 440 volts. Seeing as 480 is standard in USA and 400 is the new standard in Europe...why 440 ? Do you think they are counting on it working fine via the usual 10 percent variation rule with either voltage, or do some areas of the USA have 440 or 460 volts rather than 480 ?
09-02-2009, 07:45 AM #2
My hunch is they are going to bank on the 440 +/- 10% rating to get into all markets.
With any induction based device (solenoids / motors / transformers) - the key is flux density which is Volts / Hertz . . .
400V / 50Hz = 8V/Hz
480V / 60Hz = 8V/Hz
As far as the device is concerned - it can't tell the difference with respect to its ability to function - the only difference is that it is operating at the equivalent of a (60/50) = 120% feedrate override with respect to speed and power - certainly well within the design limits of most inductive devices.
09-02-2009, 09:00 AM #3
When Edison was getting started in the light bulb business, a batch of bulbs worked best on 110 volts, so he made that his standard. When Nikola Tesla got the power thing right and started supplying AC, there was a large enough installed base of Edison bulbs that he had to supply the same voltage. Then, over the years the power companies would want price increases, would be turned by the regulatory commission, and would counter by raising the voltage a bit, making everyone use a little more electricity, just like machinists will work on the high side of a tolerance. When they hit the 120 - 125 volt range, they had reached the end of the game because higher voltages were going to shorten lives of lamps too much. The life of a typical tungsten filament bulb doubles or halves with each 5% decrease or increase of the applied voltage. "Long life" bulbs are just made for a higher voltage, say 135V, and run derated. The higher power voltages, 240, 480, etc. are just multiples of 110, 120, or whatever. You can regard 440, 460, & 480 as equivalent, just depending on what was in vogue when they made the nameplate.
09-02-2009, 09:29 AM #4
Motion Guru - Nice lessen there. A bit over my head - but I can follow the logic just fine.
Milacron - I assume there is an X in it that you can tap high or low?
9100 - You seem to have quite of bit of this down, but are you 100% sure on the reasoning behind the voltage increase?
I don't know enymore whether I was once told - or came to the conclussion myself, but I was under the assumption that the reason for the voltage hikes was b/c demand was increasing over the yrs and there were many older lines that were at full capacity - and would cost a [not so small] fortune to replace, so by bumping up the voltage the same wires were able to carry that many more KVA just fine. And at the end of the day - KVA is all it ever really boils down to enyway.
As an asside - I keep forgetting the ratio of KVA to KW. Can someone help me out? I just wish they would use one rating or the other! (I would prefer KVA as it is simple.)
Think Snow Eh!
09-02-2009, 10:00 AM #5
KVA is indicated power, Kw is "real" power. KVA is what you measure if you measure the voltage applied to a piece of kit and you multiply it by the amount of current the kit takes. So KVA = 1000 X V X A. Now with ac you can get into the situation where the current is at zero when the voltage is at its peak, which also leads to the voltage being at zero when the current is at its peak. This happens when the piece of kit is an inductor (transformer with no load) or a capacitor. Under these conditions You will have a number for the KVA, but the KWs will be zero. i.e. no real power being consumed, because there is no energy being consumed, no heat, no power.
In real life zero KWs do not often happen, but for transformers and motors(mainly) there will be a real power (KW) , but because of the inductance, the indicated power (KVA) will be a bit greater(2-20%?).
The wiring must be rated for the KVA, because that amount of current actually flows.
The ratio real power/apparent power is called the power factor( 1 ->.8?). Electricity supply companies do not like supplying poor power factor loads as it makes their generators unstable.
The 440 V motor if you divide by 1.732 you get the phase to phase voltage which is 254. In the UK in the 1950s the mains voltage was a nominal 250, which over the years has fallen to 220 which is the new standard for the EEC, which equates to 380 V for three phase motors.
09-02-2009, 11:04 AM #6
Ox, The part about Edison's voltage choice is pretty well documented. BTW, Edison didn't invent the light bulb, not by about 50 other inventors who were first. There were already a number of incandescent bulbs on the market. What Edison did was the same thing Bic did with ball point pens and razors, make cheap, almost throwaway bulbs that solved many of the associated problems and develop the infrastructure to operate them. I say almost throwaway bulbs because the early ones used platinum leads that had to be salvaged. As to the part abut raising voltage, that is a little less certain. I don't really remember where I got it and it would be interesting to research it.
Re KW vs KVA, think of it this way. If you push on a swing at exactly the right part of its travel, all your energy goes into making it swing. If you push a little off the rhythm, part of your push is wasted. If you get very far off, you may be pushing like mad, but the swing isn't going anywhere. The energy that is utilized is KW, the effort you put in is KVA. If you are right on, KW = KVA. If you are far enough off, KVA may be high but KW is small. KW represents the work you actually utilize. Power companies hate bad power factor because they don't get paid for it but still have to absorb the greater losses in their lines and generators. As chuckey says, it can also make generators do weird things.
09-02-2009, 11:17 AM #7
There are a couple of things that play in here. We have 480 at the plant and have our own substation. We also have several machines that require 440 so we use a buck/boost on those machines. I have also seen a few machines with a 440 tap. Only the manufacturer knows for sure what their machine will take.
09-02-2009, 11:46 AM #8
There doesn't seem to be any standard anywhere. Here we have 440/460 VAC in most places and we have built machines for Europe and the voltages seem to be all over the place. The most common in Europe seems to be 380 vac but some countries have 230 vac and both cases can be 50 or 60 Hz.
We use Baldor motors on everything and there is a safety factor in the motor design that allows quite a bit of flexability with respect to voltage. We always check with the manufacturer, but we run 460 vac motors on 380 vac quite often. I wouldn't hesitate to run a Baldor 460 vac motor at 480 vac, but I can't speak for your Euro motor.
09-02-2009, 12:17 PM #9
J-head . . . if the motor is designed for 460V / 60Hz . . .
460V / 60Hz = 7.67 V/Hz
380V / 50Hz = 7.60 V/Hz
Close enough for the motors from Baldor (and most other manufacturers)
If you are the type that likes to exploit this relationship, you will figure out that you can connect a 230V motor to a 460V drive and run it at 2x rated HP at 120Hz all day long and the motor is happy as can be.
09-02-2009, 12:35 PM #10
09-02-2009, 12:51 PM #11
Would you like to add the part about where we purchase the extree 60 hz?
No idea why we would want to doo such thing to begin with?
Think Snow Eh!
09-02-2009, 12:57 PM #12
09-02-2009, 01:14 PM #13
09-03-2009, 06:54 PM #14
Ox . . . say you have a Tree J425 that you bought from craigslist for $1000 . . . and you want to get it running but the Yaskawa spindle drive is gone, the motor bearings feel lousy and the encoder on the motor is toast. You are going to spend an easy $5k - $10k if you want to fix your spindle and get it all working again like it came from the factory.
ORrrr . . . you could put in a 10HP Baldor motor that you found surplus for a few hundred dollars. Add a $125 encoder. Put in a 480V 20HP drive that you have laying around. Adjust parameters to get it to run at 230V, 60Hz at 1750 rpm . . . then it runs at 460V, 120Hz at 3550 rpm. Mount it up where the original spindle motor used to be and presto - you have a spindle motor that develops 20HP at 3600 rpm and keeps putting out 20HP all the way to 7200 rpm.
Now using a motor and drive setup that no one would likely think of you can rigid tap a 1" tap into A36 steel or spin a 1/4" end mill in aluminum at 6500 rpm . . . the motor used to run a conveyor - life is so much more exciting for it now.
It has been spinning tools now for over a year - still runs great and it is like a freight train with a big surface mill in it - never bogs down for want of torque and leaves a nice finish.
I didn't do this with a straight stick VFD although it would likely work fine - rather I used the encoder feedback and put the drive in closed loop vector mode. I get 100 Ft-lbs of torque at the spindle at stall.
After rebuilding the Yaskawa spindle motor and now putting a new encoder on it . . . I have decided to leave well enough alone - the Baldor is doing fine.
09-04-2009, 05:18 AM #15
09-04-2009, 06:20 AM #16
Not quite the situation as I understand it.
240V was the UK standard for years, with 220V in much of the rest of the EC maybe also 230V in some parts.
I believe the 'new' (it's been in place for quite a while now) EC standard is for 230V, but the rules on allowed variation have been set so that 240v is still allowed and is still the usual voltage for a lot of the UK even though the 'official' voltage is 230. It's certainly what we have here, sometimes a couple of volts higher. The 3-phase equivalent of 240 single phase is 415V.
09-04-2009, 07:33 AM #17
09-04-2009, 08:12 AM #18
In the drive setup -
Terminate motor to a 460V drive using the 230V windings on the motor
Put in the 230VAC Nameplate current (varies, but generally around 2.5 x motor HP rating = i.e. 10HP motor ~ 25Amps at 230V)
(if you are using a closed loop vector drive) Take the difference between the name plate rpm and the synchronous rpm (should be between 25 and 50 rpm for a quality motor) . . . subract this difference from double the synchronous speed and put this in for the new nameplate motor rpm. i.e. if the nameplate rpm is 1765, (difference is 35 rpm) . . . synch speed is 1800 rpm, setting is now 1800*2-35 = 3565 rpm.
Put 120Hz in as the motor nameplate frequency
Put 460V in as the motor nameplate voltage
09-04-2009, 08:44 AM #19
I wish everyone would get together on all this. I have worked with two companies that had 120/208 services and all 240 V equipment. Nothing ran right. The motors on molding machines ran so hot you could cook lunch on them and the heaters never delivered full heat. The management wouldn't bite the bullet and put in transformers to supply 240 V and kept playing around piecemeal with buck and boost transformers.
At least 25 cycle AC seems to have died. I worked in a plant that had old 25 cycle equipment and Union Electric had to bring it from Keokuk to St. Louis. I would think that it would have been cost effective for the power company to pay for new equipment to get rid of it.
09-04-2009, 04:43 PM #20
Power line Voltages are NOMINAL. This is definitely the case in the US and I strongly suspect it is the case in Europe and other regions as well. There are fixed ratios between the various nominal Voltages and these ratios are determined by the number of windings on the transformers in the power grid. There is a basic 1, 2, 4 times ratio between the three most commonly used Voltages: 120, 240, 480. Oh, and for three phase, there is a 208 number in there. It is derived as the Voltage present between any two of three 120 Volt legs that are each grounded on one side. A bit of trig will show the relationship. I am sure there are multiples of this Voltage also, probably X2 and X4 (416 and 832 but they are probably rounded to something like 415 and 830)
The various power companies will have different target Voltages for the numbers in this series and for the lowest one, 120 Volts it can range from perhaps 110 to as much as 130 or about +/- 10%. This is just like the tolerances we see on blueprints (+/-0.003" for instance). The actual range and tolerances WILL vary from one power company to another.
When the load on a system changes the power plants can not change the speed of the generators instantaneously so the Voltage may drop or go up for a while. This allowable tolerance range allows this to happen and the manufacturers of electric devices MUST take these variations into account so no damage is done. Yes, a given motor will develop more HP when the Voltage goes up. And less when it goes down. This is just part of the game.
So the ranges look like this:
Low End: 110, 220, 440, 187 (208 - 10 %)
Nominal: 120, 240, 480, 208
High End: 130, 260, 520, 229 (208 + 10%)
Thus any number on the nameplate of a motor between 440 and 520 (yes, that's 520) would represent the SAME design point. A motor that says 440 should run at Voltages up to as much as 520 with little shortening of it's life. It may even run OK at Voltages that are somewhat higher or lower than this range. And none of the Voltages in the range should be considered abnormal in any way. I have a mill who's motor is rated at 220 but it has been running quite fine on 208 for years now. Not an ideal situation, but it does work and so far there is no apparent damage.
Don't get humg up on exact Voltages. If you put a recording Volt meter on the power line at any location in the world, you will find that it fluctuates by a considerable range over a period of a day or a week. I encountered an extreme example of this when I worked as a transmitter engineer at a TV station in the New Orleans area. There was an aluminum refining plant on the same grid as the transmitter facility and they would sometimes fire up an additional furnace in the evening hours. The first time I saw this happen, ther building lights dimmed severely and all my TV and audio monitors stopped working. I first thought the transmitter was off the air and I was going to try to restore operation when the people at the studio called me and asked what was happening. They said that the picture got dimmer but was still there. They were miles away and apparently the line Voltage was normal there. When I read the power meters on the transmitter I saw they were at about 35% of normal and the power line meters were reading about 80 Volts instead of the normal 120. The line Voltage slowly came back up over a period of about an hour as the power companies were able to adjust for the increased load. Yes, it really took them that long. There was nothing I could do but wait. At 80 Volts, the power was clearly out of tolerance but the transmitter still operated at this reduced power level with no damage. This included not only the electronics, but also the large blower motors the were used for cooling it. Only the monitors failed to work. Power line Voltages DO vary, sometimes by very large amounts.