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Amp draw 650 HP Mtr. #207092 09/21/12 03:26 PM
Joined: Mar 2003
Posts: 849
Y
Yoopersup Offline OP
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650 Hp Mtr. 575volt 3 phase.
Requires 480v we have .
/575 buck boost to run.
Questions??
Current draw on 480v side??
Current on 575 side side ??
Mtrs coming in from Canada as we run mostly 480 in USA we're running into this more often.

2017 / 2014 NEC & Related Books and Study Guides
Re: Amp draw 650 HP Mtr. [Re: Yoopersup] #207122 09/24/12 01:11 PM
Joined: Mar 2003
Posts: 849
Y
Yoopersup Offline OP
Member
???????
I can't believe I'm the only one that works with this stuff?????
We Have 480 3 Phase
The motors coming in 575 Volt
We need Buck Boost Transformer.
Amp draw Pri. Of buck boost (480)
Amp draw Sec, of buck Boost (575)
Breaker size on Pri. to hold Mtr starting on Secondary.

Re: Amp draw 650 HP Mtr. [Re: Yoopersup] #207123 09/24/12 01:17 PM
Joined: Jul 2004
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gfretwell Offline
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Deeper water than I ever swam in wink

What is that driving?


Greg Fretwell
Re: Amp draw 650 HP Mtr. [Re: Yoopersup] #207124 09/24/12 04:51 PM
Joined: Jul 2007
Posts: 1,335
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sparkyinak Offline
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I'd would work with a supplier and have them size it and if it don't work, its on them. I just read too that VFD's can be used as softstarters too and give the motor flexibility where a softstarter can't


"Live Awesome!" - Kevin Carosa
Re: Amp draw 650 HP Mtr. [Re: Yoopersup] #207127 09/24/12 09:05 PM
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twh Offline
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I haven't worked with a buck/boost transformer, but the relationship between voltage and current is inverse. It can't be anything else unless you have a pit where the extra va go. You need the flc of the motor. You probably need to size the transformer with the same factor as the conductor size. Does that help?

Re: Amp draw 650 HP Mtr. [Re: Yoopersup] #207128 09/24/12 09:13 PM
Joined: Apr 2002
Posts: 7,218
HotLine1 Offline
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Yoop:
Your best bet would be to hunt down a electrical 'power' engineer.

Maybe Scott35 will jump in here on this, but I'm in with Greg...that water is much to deep.

Looking at 430.250, I would take a stab at an FLA of 800 amps @ 480 and 640 @ 575. Just using an approx 20% diffeence from 480 to 575.

Could you not use a 480 primary, 575 secondary transformer, instead of a buck/boost.



John
Re: Amp draw 650 HP Mtr. [Re: Yoopersup] #207130 09/25/12 08:36 AM
Joined: Oct 2000
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Scott35 Online Happy
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Yoop,

What is the FLA of the Motor at 575V?

Use the KVA input rating of the Motor to configure the Transformer size and input FLA at 480V.

Your Voltage Increase will be 95 Volts (575 - 480 = 95), so a standard "Buck-Boost" type Transformer is not an option; the highest Secondary Voltage I know of is 48V.

An Autotransformer (pre-wound), or typical Isolated Transformer (575V to 480V Closed or Open Delta) arrangement may be needed.

Anyhow, obtain the FLA at 575 Volts to obtain the Motor's Full Load KVA, which may be converted to Transformer Capacity and Motor FLA at 480 Volts.

Example:
If the 650 HP Motor's Nameplate FLA is 640A at 575V, the KVA will be 637.44 KVA (637,440 VA)
At 480V, the FLA becomes 767.08 Amps.
The Transformer will require a Secondary with 750 KVA Capacity.
For a Buck-Boost with 95 Volt Secondary, that would result in 150 KVA capacity - as either:

1: For an Open Delta arrangement: 2x 75 KVA,
2: For a Wye arrangement: 3x 50 KVA

You might obtain (2) Single Phase 480V x 120V Transformers in 100 KVA Capacity, which you could configure in an Open Delta Network. This arrangement will result in 600V output.
Each Secondary will need to be rated at least 76.8 KVA (120V x 640 Amps = 76,800VA).

Good luck!

-- Scott (EE)


Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!
Re: Amp draw 650 HP Mtr. [Re: Yoopersup] #207132 09/25/12 01:50 PM
Joined: Apr 2002
Posts: 7,218
HotLine1 Offline
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Scott:
That's clear as a bell! Thanks from me to you!
Now, Ernie....it's up to you.
I'm curious to see if my 'guesstamate' was close.


John
Re: Amp draw 650 HP Mtr. [Re: Yoopersup] #207135 09/25/12 08:53 PM
Joined: Mar 2003
Posts: 849
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Yoopersup Offline OP
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Its for a Mining Drill bore.
Let ya know what was done when its decided/
Just Kinda wondering if its hooked to a Buck/Boost.
Would it draw the same on the 480Volt side of the Buck Boost
as if it was running on 480 not 575.
I've run 575 mtrs on 480 before but never this Big.

Re: Amp draw 650 HP Mtr. [Re: Yoopersup] #207160 09/29/12 01:34 PM
Joined: Oct 2000
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Scott35 Online Happy
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John;

Quote

That's clear as a bell! Thanks from me to you!


Cool! Thanks for the nice words!

Yoop;

Quote

Just Kinda wondering if its hooked to a Buck/Boost.
Would it draw the same on the 480Volt side of the Buck Boost
as if it was running on 480 not 575.


Input KVA will match the Output KVA, per the Motor's Load.

i.e.: If the Motor is producing 100 HP, on the 460V Input side, the load would be 123.7 Amps, and the Apparent Power input would be 98.82 KVA.
On the 575V Output side, the Motor would be drawing 99.2 Amps, and the Apparent Power output would be 98.82 KVA.

-- Scott (EE)


Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!
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