Hello I am inquiring on all of your thoughts on stepping up from 240v delta 3ph (180onB) to 480 and the correct transformer to utilize.I see many answers to stepping up and I'd like to inquire on which one would you use? We have two water pumps 10hp each and I am told by the pump guy that using them at 230v would reduce the hp by 1/3. Your thoughts are appreciated on this and the Cat# of the Xfrmr in a outdoor location> 200a 240v 3ph QOB to step up to 480 to feed 2 combos sz 0 to water pumps approx.13a apiece 100' away. Thanks in advance for sparing me the salesman !!
Step Up Transformer Question
- Thread starter _KJ_
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Electric-Light
Senior Member
The pump guy is clueless.
You only need a 6AWG to carry 52A @ 240v as opposed to 10AWG at 26A @ 480v. The only cost difference is what a 100' run of 10AWG costs vs 6AWG which is not enough to bother with a transformer.
You only need a 6AWG to carry 52A @ 240v as opposed to 10AWG at 26A @ 480v. The only cost difference is what a 100' run of 10AWG costs vs 6AWG which is not enough to bother with a transformer.
- Location
- New Jersey
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- Journeyman Electrician
Why would a dual voltage motor have a 1/3 lower output when used at the lower voltage?
confused
confused
confused
i guess i need to get my books back out because I'm confused after reading this.
Do we know that it is dual voltage?
- Location
- San Francisco Bay Area, CA, USA
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- Electrical Engineer
It's because the Flygt pumps are made in Sweden with motors that are designed as dual voltage, but for voltage distribution systems that are nominal 400/230V 50hz 3 phase 4 wire systems where you connect the motor in Star (Wye) for the higher voltage and Delta for the lower voltage. The fact that our voltage is 480V 60hz means you can run those motors just fine at the higher voltage because the V/Hz ratio is the same, BUT because the frequency is 20% higher, you get a 20% higher HP output. That's why when you look at a Flygt pump, the HP ratings are weird values like 88HP. That's really a standard 55kW 400V 50Hz motor that when run at 60Hz, becomes a 66kW motor, which nets out as 88.47HP (they just round it down to 88HP).
But what happens when you connect them to 230V 60Hz is, the V/Hz ratio is no longer the same as it was designed for, so the torque output is lower and in order to keep from overloading the motor, you have to de-rate it because of the loss of torque. So if we use the above example, that 55kW motor at 230V 50Hz had a V/Hz ratio of 4.6:1, but if you connect it at 230V 60Hz, it is only 3.83:1, so 17% lower and the peak torque capability drops by the square of this difference, so the power capability of the motor drops to 70% of what it is rated for, or to be safe, 2/3.
Or to boil it down to a nugget,
"The pump guy is NOT FOS".
But what happens when you connect them to 230V 60Hz is, the V/Hz ratio is no longer the same as it was designed for, so the torque output is lower and in order to keep from overloading the motor, you have to de-rate it because of the loss of torque. So if we use the above example, that 55kW motor at 230V 50Hz had a V/Hz ratio of 4.6:1, but if you connect it at 230V 60Hz, it is only 3.83:1, so 17% lower and the peak torque capability drops by the square of this difference, so the power capability of the motor drops to 70% of what it is rated for, or to be safe, 2/3.
Or to boil it down to a nugget,
"The pump guy is NOT FOS".
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- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
As to the cost of running it 230 vs 480V, it all depends.
Flygt pumps are generally sewage lift station pumps where pumping cost is a function of lift and flow. If you get less lift from that pump at 230V (assuming of course that it is still enough to lift it to where it's going), you will get less flow. Less flow in a lift station means that for the same given amount of "influent", the pump will have to run longer to accomplish the task of emptying the tank. Given the same mechanical setup, at 480V the pump will run more efficiently but you will lose efficiency through the transformer. I would hazard a guess that the transformer losses will be less than the added kWh from the motor having to run longer in the 230V scenario.
Flygt pumps are generally sewage lift station pumps where pumping cost is a function of lift and flow. If you get less lift from that pump at 230V (assuming of course that it is still enough to lift it to where it's going), you will get less flow. Less flow in a lift station means that for the same given amount of "influent", the pump will have to run longer to accomplish the task of emptying the tank. Given the same mechanical setup, at 480V the pump will run more efficiently but you will lose efficiency through the transformer. I would hazard a guess that the transformer losses will be less than the added kWh from the motor having to run longer in the 230V scenario.
Leestarkweather
Member
- Location
- Los Angeles CA
Great discussion
Great discussion
This is why I read this board. The OP left out a critical spec (the Swedish motor mfg. and the nameplate info re voltages) and several responders assumed it was a US NEMA 230/460V Motor. (Assume made an ass out of you but not me). Anyway, then the OP gives the crucial info, and a very knowledgeable response explains exactly why the Pump Vendor was not FOS. So, I learned something (it's similar to a lot of things I learn about International Electrical Equipment, which is more and more available in the US) and also witnessed an excellent response. Hats off to Jraef.
Great discussion
This is why I read this board. The OP left out a critical spec (the Swedish motor mfg. and the nameplate info re voltages) and several responders assumed it was a US NEMA 230/460V Motor. (Assume made an ass out of you but not me). Anyway, then the OP gives the crucial info, and a very knowledgeable response explains exactly why the Pump Vendor was not FOS. So, I learned something (it's similar to a lot of things I learn about International Electrical Equipment, which is more and more available in the US) and also witnessed an excellent response. Hats off to Jraef.
If it's a centrifugal pump, it would need (1.2)^3 more power at the higher speed. All other things being equal.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
In the US the supply voltage choice is 240V 60Hz or 480V 60Hz other than that , the V/Hz ratio is the issue.
Most US motors reconnect 230V windings into parallel or series combinations and then into a delta configuration for either 230V or 460V. As Jraef mentioned, the Europeans usually reconnect 230V windings in delta or wye to get 230V or 400V.
Electric-Light
Senior Member
If it's sold in the US, I would think that they'd fit it with a 3475/1725 RPM spec impeller. I don't think I was wrong to assume it was a dual voltage NEMA motor, with the amount of information given by the original poster in their first post.
I agree. I was just trying to gently nudge Jraef into looking at the application rather than just the V/Hz ratio.
Indeed. Limited information in the original post.
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