NEMA Premium and IE3 for submerged motors

[Clyde38]

Does anyone have an understanding of how NEMA Premium and IE3 standards will effect submerged motors? In particular, I'm referring to a motor submerged in hydraulic fluid as a pump for a hydraulic power unit. Internet searches show "Motors completely integrated into a machine (pump, fan, or compressor) that cannot be tested separately from the machine" are exempt from the standards. Of course how reliable are internet searches?

 

[KllrWolf]

Is the motor a fluid filled motor, or just one sealed to keep out the hydraulic fluid?

 

[Clyde38]

KllrWolfc - The motor is fluid filled, not sealed.

 

[KllrWolf]

What is the Hp of the motor?

I have designed fluid filled motors for mainly operation in ocean conditions, but have also done some for other fluids, including hydraulic fluid. The smallest has been about 2.5 Hp. The motors are sealed, but the purpose of that seal is to keep various junk in the ambient fluid from entering the motor, and to keep the internal fluid in the motor during transport, storage and installation. The manufacturer of the motor should be able to test it, even if the motor uses the pump as its mounting cover and seal (have made some like this before). The tests need to be modified for the special circumstances of the motor. Of course, normal efficiency and other running data will be different for the fluid filled when compared to the same size standard motor.

 

[Clyde38]

KllrWolf - The motor is a 60 HP four pole machine. I would like to know if this motor, as a submerged unit can even be name-plated NEMA Premium or IE3. I am interested in improving the efficiency of the system by exchanging the existing standard efficiency motor with a NEMA Premium or IE3 motor. Does the high efficiency nameplate rating still apply to the motor once it is submerged? My guess is that it doesn't. In that case the system can't claim the high efficiency rating. Ultimately the goal is to improve the efficiency of the entire system and one of the improvements would be the motor. Standards are meant to help, but unless one is current in the interpretation of the standard it can be confusing. Not to mention that to purchase the standard and to begin to read and understand it is expensive (for me anyway).

 

[KllrWolf]

If the motor nameplate performance is listed for the motor being submerged, then yes you can use the motor nameplate. I know that none of the fluid filled motors my company deals with (either new designs or older repairs) will meet the premium efficiency rating due to the drag caused by the internal fluids on the rotor and their circulation in the windings and air gap. Of course, just because we deal in a niche market, there might be other motor designs called submersible that can have better specs due to different operating environments.

 

[VLTPumpControl]

Both NEMA Premium and IE3 only specify a specific motor efficiency curve to be maintained to reach this efficiency level. Neither discuss the application itself. Submerged motors need to be designed for this purpose and if the manucaturer state NEMA Premium or IE3, this has to be for when the motor is submerged, but I would check with them to be sure.

If you want to increase system efficiency, you should consider applying VFD (unless you already do off course). In a large range of application, where speed control does not make sense, pumps are often throttled to match the flow exactly to the requirement. In some cases the valve might be 20% closed, so open the valve fully, reduce the speed and you will save more energy and your VFD is paid back in less than 2 years. You can read about such a case here. While the characteritics of hydraulic fluid is different from water the physics still apply, although realised energy saving will be slightly different.

If you can then improve your controls to take advantage of the speed control, off course payback is even shorter

Another thing is that permanent magnet motors are often referred to as "Super Premium" or IE4 motors, but we are introducing a new motor mounted drive this year and wanted and IE4 motor for this and many of the PM motors we investigated, where only IE3 and some even IE2, so make sure you do not select a new motor based on motor technology, but do it based on data from the manufacturer and even then I would advise testing the performance as well.