Inverter-duty motors

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propower34

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I have been asked to connect a submersible pump (split case; 480V 3 phase) to a VFD.

The motor is not rated for inverter-duty, but I have been instructed to connect it anyway. We will not have power available for several more months, so I still have time to do research.

Does anyone have experierience or knowledge of operating a non-inverter-duty motor on a VFD?
 
check to see the limits of the cable length if you are planning to operate the pump from a considerable distance from the VFD. VFD manufacturers often place maximum limits on the cable length from the VFD to the pump.

the problem with connecting a non inverter duty pump is the extra heat the motor will be subjected to. the motor must be operated in a colder place to compensate for this additional heat.
 
Check the web site for your pump motor. Franklin has an excellent site. Generally the pump motor will handle the drive but the pump itself has to come to half speed, 30 hz within one second to prevent damage to the pump. The drive will have different parameters to set for use with pumps. Lead length to the motor will be a problem but ordering the proper drive accessories will help that.
 
The inverter rated motor means the winding insulation has a higher rating. Make sure the motor lead lengths are reasonable, <100 feet or so. If they are longer install a 3% output reactor to limit the capacitive coupling the VFD will generate on the leads. It should be OK, just take the necessary design precautions.
 
I have three 200 hp deep well submersible pumps in operation on VFDs. The motors are not inverter rated and the lead lengths range from 500' to 1900' between the drive terminals and the motor. We do have load side reactors at the drives. These have been in operation for about 6 years with no problems. The minimum speed setting on the drives is 50%.
Don
 
I didn't know you could get a 200 HP submersible! That thing must need a crane to be lowered down the hole.

What on earth do those pump? What size casing do they fit in?

Learn some random stuff on this forum every day!
 
The casing is 16 or 18" and the piping is 10 or 12". These pumps are the water supply for an industrial plant and at full speed each pump puts out about 1300 gpm. The use a derick rig to install the pumps and the piping. The pumps are about 500' deep. The discharge pressure is about 300 psi leaving us about 100 psi at the surface.
Don
 
don_resqcapt19 said:
The casing is 16 or 18" and the piping is 10 or 12". These pumps are the water supply for an industrial plant and at full speed each pump puts out about 1300 gpm. The use a derick rig to install the pumps and the piping. The pumps are about 500' deep. The discharge pressure is about 300 psi leaving us about 100 psi at the surface.
Don
Click to expand...
Wow!!! Good luck getting a permit to drill one of those suckers out here in NE.
 
Wow!!! Good luck getting a permit to drill one of those suckers out here in NE.
Click to expand...
This is common in this area for both municipalities and industrials. The actual well is about 1200' deep with the pumps set at about 500'. They were at about 400' a number of years ago, but declining water levels required them to be lowered another 100'. That also required in an increase in horsepower from 150 to 200.
Don
 
I currently have two 350 hp submersible pumps 1100 ft deep that are started by Soft-Starts to limit torque on the pipe - (18" casing 12" pipe). Due to weight considerations the pipe for these pumps is made of fiberglass. The 350 hp motors are 14 ft long, this type of motor design tends to create a load imbalance on the three-phase current & a non-centered shaft flux can develop. In a VFD application with this type of motor I would be concerned with circulating current in the shaft & bearings due to this flux offset causing flutting in the bearings. I would reccomend at least shaft grounding brushes or at least one isolated bearing (or ceramic bearing). I have many VFD's running non-VFD rated motors - on new installs we buy VFD rated motors to increase motor life.
 
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