ptonsparky
Tom
- Occupation
- EC - retired
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?
Pretty much what I had assumed, although the need to recalculate manually hadn’t occurred to me.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.
460 is default but it would accept 480.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.
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 labelI 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?
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.... He said drives are rated for ampere and not HP but drive labels always had a maximum HP on their label
Wow a 12 pole motor. In my 50 years as a sparky a 6 pole was the most poles that I ever came across. a 12 pole motor running on 60 Hertz would run around 600 RPM. Motor with 12 poles guess cost a lot of money but for a slow speed operation might be able to get away with a small or no gearbox. While I was an apprentice back in early 70's my company purchased a 125 HP Syn. motor from an old movie theater to drive an ammonia refrigerant compressor. I told them they were wasting money on a 50 year old motor. Had to send motor out to a rewound shop then sent control panel out several times for a white elephant that could not start under load and cost over 8 grand in total repairs along with a crane rental and never ran more then a hundred hours before burning up.. That motor ran slower then the average 4 pole 1760 RPM motor but not sure how many poles it had. Right before I retired they got a pumping station that they had the 2 10 or 15 HP pump motors programed for VFDS to run 10% higher then motor nameplate speed. I complained that this mostly likely would shorten the life of the motors but they stated they do that all the time. we did PM"s on all VFD"s from once to 4 times a year but I never got a chance to see if they set motor amps higher then nameplate amps due to higher speed.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.
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.