Cable and fuse size for VFD

[EPZJB]

Hi guys, I have a new 150hp VFD. The instruction recommand to use 350MCM CABLE, 250A FUSES at 480v supply. The question is I want to connect the VFD with 380v supply, how to size the cable and fuse? May I use the same size as working on 480v? And I check the VFD, it can be connrcted to 380v/60Hz.

Thank you very much.
Waiting on line.

Bill.z

 

[jraef]

Assuming that because you are supplying 380V it is not going to the US, the cable size should conform to whatever code standards exist at your destination. Technically the maximum current capability of the VFD remains the same, so either your motor will provide less HP or you have made sure the VFD is sized properly for the increased current to produce 150HP with that lower voltage.

Thye VFD couldn't care less if it is 50 or 60Hz input, all it does is rectify the AC to DC.

JRaef.com
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[bitsian68]

The VFD sized to deliver 150HP at 380V should be a 245A (for example to ABB ACS550-U2-245A-4) unit, will require a 250A fuse (fast acting) and 350MCM cable. Same VFD can deliver 200HP at 480V.

 

[jraef]

Yes, but he said at the outset that he already has the VFD and it is a 150HP 480V version, which according to ABB should be either a 180A if it is a "Normal Duty" version, or 196A if it is a "Heavy Duty" version. If it is a 180A drive and he hooks it up to a 380V supply, the current remains 180A, so the HP of the motor must be reduced by the same ratio as the voltage ratio, roughly 20%. This makes the maximum motor size that can be connected to the drive at a 380V supply 120HP. I only brought that up as a warning against connecting that drive to a 150HP motor without taking this into consideration. If on the other hand he needs 150HP at the load shaft, he will need to buy a bigger VFD.

Either way, the cable size is determined by the max. amp rating of the VFD, which does NOT change with voltage. It will either be 180A or 196A depending on how it was purchased. He has what he has at this point.

JRaef.com
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[ScottyUK]

At this power level a 3-phase 380/480V autotransformer would be significantly cheaper than a new drive if he needs full rating from the existing drive.



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Sometimes I only open my mouth to swap feet...

 

[jraef]

Agreed, good point.

Sometimes my old habits as a VFD sales engineer come back to haunt me.

JRaef.com
"Engineers like to solve problems. If there are no problems handily available, they will create their own problems." Scott Adams
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