I'm attempting to bid a new VFD conversion project, where the customer is changing out a 4160V 2500HP motor for a 575V 2500HP pump motor, and adding a step down XFMR, power filter and VFD. (Lower voltage VFD much cheaper) The primary 4160V is fed from a fused switch (old starter), and will feed the new transformer. I'm trying to size the fused service disconnect, and the problem is I have no motor nameplate data because it hasn't been ordered yet. Rule of thumb is one horse=one amp for 575V motors, but I'm new to this voltage. Any ideas? Wouldn't the disco and time delay fuses need to be 4000A? Starting current shouldn't be a big issue, unless at a later date the VFD gets bypassed- it happens. Thanks for your opinions.
575V 2500h.p. pump service
- Thread starter danger30
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Tried to find info for a 2500 hp at 575 volts but could not. NEC lists a 500 hp at 575 volts with a FLA of 472 amps. Using that figure the 2500 HP FLA would be about 2360 amps. You will need at least a 3000 kva transformer with a primary FLA of 418 amps. 418 x 1.25 = 522 amps. I do not know what the next size fuse is but it may be a 600 amp fuse not 4000 amps. A solid state starter should allow the motor to start with no problem if you can find one. Forget about the bypass. You can not start the motor across the line.
Personally I would keep the 4160 volt motor.
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Cold Fusion
Senior Member
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- way north
There are several options for VFD's, so I'm going to end up giving two bids (with or without bypass). So would I Figure 125% rated input of VFD for non-bypass type, and 125% of motor FLA for bypass type to determine service size (main fused disconnect)? What about fuses? Thanks for your thoughts
I would say the highest of the two ?
Sounds like a good application for a Static Kramer or Improved Static Kramer.
Probably cheaper, certainly more efficient and you get bypass for free.
weressl
Esteemed Member
If the issue is the cost of the ASD, then you should investigate the cost and compare the cost of a 2500HP/575V motor to simple step up transformer. Such motor would be a 'white elephant', a custom motor which would be difficult to replace or repair and has a higher failure rate than a static equipment such as a transformer. The LV ASD will also have a high component count, compared to the MV, that will also result in a lower reliability number.
drbond24
Senior Member
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- Barboursville, West Virginia
I'm throwing my vote in with the others that are avoiding your question and telling you to stay with the 4 kV motor. 
I cannot imagine that it is a good idea to have a 575 V 2500 hp motor. Like Laszlo said, it would be a special make that would give you endless problems.
I cannot imagine that it is a good idea to have a 575 V 2500 hp motor. Like Laszlo said, it would be a special make that would give you endless problems.
Fulthrotl
~Autocorrect is My Worst Enema.~
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i'm dumb, and bored on a monday, so i went off looking for LV motors above
500 hp, as i'd never seen one, and wondered a bit....
so i went off and googled 575 volt 2500 h.p. motor, and the only place
they seem to exist on google is in this thread, right here.
low voltage motors seem to dry up about 800 hp, and i admit to having never
seen anything above 500..... where do you get these? do they really exist
outside of this thread?
randy
weressl
Esteemed Member
i'm dumb, and bored on a monday, so i went off looking for LV motors above
500 hp, as i'd never seen one, and wondered a bit....
so i went off and googled 575 volt 2500 h.p. motor, and the only place
they seem to exist on google is in this thread, right here.
low voltage motors seem to dry up about 800 hp, and i admit to having never
seen anything above 500..... where do you get these? do they really exist
outside of this thread?
randy
For money, somebody will make anything......
Cow
Senior Member
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- Eastern Oregon
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- Electrician
For money, somebody will make anything......
I'll bet
You have to wonder if the customer wouldn't be better off using 5-500HP motors, if possible, seems like a little redundancy would help in case one motor goes down.
Ill get more info on the motors tomorrow and I'll let you know. The project is for the Bureau of Reclamation, which recieved a very large stimulus check. This may end up being a test. If the efficiency/power cost isn't there with the 575V they can change it back to 4160V fairly easy. If they do see saving they will probably order a spare motor.
Fulthrotl
~Autocorrect is My Worst Enema.~
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zbang
Senior Member
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- Roughly 5346 miles from Earls Court
it'll probably look something like this, right?
Hoover Dam, Nevada side? (IIRC, that piddly little thing in the right foreground is something like 2MW for house power- 4' Pelton wheel with +500' head.)
drbond24
Senior Member
- Location
- Barboursville, West Virginia
Cool! There is a level in a 1st person shooter game I have that looks exactly like that picture.
I think it is Tom Clancy's Rainbow Six...
Come to think of it, in that level the bad guys are trying to blow up a hydroelectric dam. Ha! I knew my time spent playing video games would pay off someday. :wink:
I think it is Tom Clancy's Rainbow Six...
Come to think of it, in that level the bad guys are trying to blow up a hydroelectric dam. Ha! I knew my time spent playing video games would pay off someday.
:wink:it'll probably look something like this, right?
Ah, they don't make 'em like the used to.....
Thats a good point.i'm dumb, and bored on a monday, so i went off looking for LV motors above
500 hp, as i'd never seen one, and wondered a bit....
so i went off and googled 575 volt 2500 h.p. motor, and the only place
they seem to exist on google is in this thread, right here.
low voltage motors seem to dry up about 800 hp, and i admit to having never
seen anything above 500..... where do you get these? do they really exist
outside of this thread?
randy
At 575V, the rated current would be in the region of 2400A.
Building it might be a bit of a challenge.
As far as I recall, the largest LV motors where we have built VSDs are around 630 kW which roughly corresponds to your 800 hp.
Probably there are others larger or even much larger but just maybe it shows where there is a natural break between standard and custom build for special purpose.
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