MV VFD heat load?

[Dale001289]

Has anyone ever calculated the heat load for a MV (4160V) Variable Frequency Drive with a 500hp motor? I'm being told its around 15000W (or 50000 Btu's) which translates to about 4 tons of cooling if 12000 Btu = 1 ton. This seems very high to me.

 

[nhee2]

Eaton's catalog lists average heat loss for their MV drives at 25W/hp, which would be 12,500 W for a 500 hp motor. So same order of magnitude as what you have been told.

 

[Dale001289]

Eaton's catalog lists average heat loss for their MV drives at 25W/hp, which would be 12,500 W for a 500 hp motor. So same order of magnitude as what you have been told.

thanks I will check Eaton's cat

 

[don_resqcapt19]

If you assume the motor is a perfect motor, 746 watts per hp, the motor would need 373,000 watts, so if the heat is 15,000 watts that is about 4%. Maybe a bit high, but not that much.

You should be able to get the heat information the drive manufacturer.

 

[petersonra]

Has anyone ever calculated the heat load for a MV (4160V) Variable Frequency Drive with a 500hp motor? I'm being told its around 15000W (or 50000 Btu's) which translates to about 4 tons of cooling if 12000 Btu = 1 ton. This seems very high to me.

the manual usually tells you what it is. it is likely different for every brand or part number of drive.

i can tell you from experience that no amount of forced ventilation will remove enough heat from a normal sized enclosure that has a 200HP 480V AB drive in it unless you use the option to mount it with the heat sink out the back of the cabinet. the fact that people do this all the time w/o mounting the heat sink out the back suggests to me that the drive almost never runs at full load under worst case conditions. My understanding is that the worst case is really bad, but that even a little under worst case the heat generated is substantially less.

 

[Jraef]

Be careful when reading sales literature for info like this. one thing some mfrs do is give you the heat rejection of the drive itself, but you must use a multi pulse transformer arrangement to make the drive work , and they leave out the transformer losses. The same is also true of output filtering, which is common in some MV drives. Any decent mfr should be able to give you that data in writing specific to your drive, and nobody in the MV drives business could be there if they made junk or treated users poorly. Just don't rely on sales literature. That stuff is written by marketing people.

 

[Dale001289]

Be careful when reading sales literature for info like this. one thing some mfrs do is give you the heat rejection of the drive itself, but you must use a multi pulse transformer arrangement to make the drive work , and they leave out the transformer losses. The same is also true of output filtering, which is common in some MV drives. Any decent mfr should be able to give you that data in writing specific to your drive, and nobody in the MV drives business could be there if they made junk or treated users poorly. Just don't rely on sales literature. That stuff is written by marketing people.

According to Eaton’s Consulting Application Guide, heat loss (SC 9000EP Medium Voltage Variable Frequency Drive Frame A) is 11500 watts for a 500hp motor. This translates to approximately 39239 Btu/hr which will require 3.2 tons of cooling @ 12000 Btu per ton. Your comment about marketing is duly noted and all so true.
I’ll definitely need to review the existing HVAC system against the increased heat load.

I appreciate the feedback from all participants in this thread!

Dale