VFD 460 vs 480

Macbeth

Member
Location
Livonia NY
Enter what is on the name plate. Lets say the name plate ratings are 50Hp, 460v, 60hz, 3ph, 65a, 1756rpm, this is what the motor is rated for and what the VFD needs to know. if you input different voltage you then need to recalculate hp, and amps for the voltage you are entering. its just way easier to enter nameplate. The VFD uses motor data for protection calculations.
 

ptonsparky

Senior Member
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
Electrical Contractor
Enter what is on the name plate. Lets say the name plate ratings are 50Hp, 460v, 60hz, 3ph, 65a, 1756rpm, this is what the motor is rated for and what the VFD needs to know. if you input different voltage you then need to recalculate hp, and amps for the voltage you are entering. its just way easier to enter nameplate. The VFD uses motor data for protection calculations.
Pretty much what I had assumed, although the need to recalculate manually hadn’t occurred to me.
Easier is close enough.
 

Jraef

Moderator
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
Are you saying the VFD does not give you an option for entering 460V? Seems odd if that's the case. Must be a foreign drive, they often don't understand how things work here.
 

Jraef

Moderator
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
then program it for what the MOTOR nameplate says, should say 460V. that is what determines the V/Hz pattern the VFD puts out to the motor, you want that to match.
 

garbo

Senior Member
I usually enter the nameplate voltage of the motor, 460, into the VFD parameters. The VFD we have would accept 480. Is there a reason not to use 480 and/or is there an advantage to using 480?
At the large hospital/research/office building that I retired from the 2 separate companies that we paid for starting up all new drives always used 480 volts. That is what the over maybe 500 drives were feed from. The few hundred dollars these great service companies charged extended the free parts & labor warranty to 3 years. Always entered the motor nameplate amps into drive parameter. Salesmen that I always ordered replacement drives always wanted to know motor amps. He said drives are rated for ampere and not HP but drive labels always had a maximum HP on their label
 

Jraef

Moderator
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
... He said drives are rated for ampere and not HP but drive labels always had a maximum HP on their label
UL requires a HP value on the label. But he was right, you MUST look at amps, not HP. VFDs are generally sized for the HP of a 4 pole motor, knowing that the FLA of a 2 pole motor will be less, so that's fine. But where you can get in deep kimchee is if your motor is 6 poles or more.

I once had to look into a problem with some "250HP" 12 pole motors that had a motor nameplate FLA of 421A! The contractor had bought the drives based on HP, but the 250HP drives were rated for 302A max. So they would go into current limit and not allow the motors to run full speed. The contractor had no choice but to buy new 350HP drives that were rated for 430A. That was an expensive lessen for him.
 
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