|
The Statement of Efficiency of the P-Base, High Thrust Vertical Motor
The efficiency of the high thrust, P-Base vertical motor is not defined by EPACT. Therefore efficiency and efficiency parameters will vary, somewhat, from motor manufacturer to motor manufacturer. In general, vertical motors are available with NEMA standard efficiency and NEMA premium efficiency.
There are several factors, unique to the High Thrust vertical motors that may or may not be included in the statement of efficiency.
The effects of thrust are not included in the statement of motor efficiency. The additional losses due to thrust are either included in the pump efficiency or are added to the motor only losses. When adding thrust losses to motor losses, they are generally estimated from the following equation:
0.0075 HP per 100 RPM per 1000 pounds thrust
High thrust motors are available with several thrust bearing options. Published efficiency is generally stated for standard high thrust bearings. The additional losses for higher thrust bearings must be obtained from the motor manufacturer.
Efficiency is confirmed by testing per IEEE 112. The preferred method is by direct dynometer testing. Most dynos, unfortunately, are arranged for horizontal foot mounted motors. Therefore vertical motors cannot be tested with high thrust bearings. It is common practice to replace the thrust bearing with a deep groove, radial bearing and horizontal mount the vertical motor for conformational testing. While this efficiency is sometimes used to state efficiency, the preferred method is to correct the tested efficiency by replacing the horizontal bearing losses with the actual thrust bearing losses.
There are additional factors that also affect the accuracy of efficiency confirmation.
- The most common lubrication for thrust bearing is oil bath. The thrust bearings are submerged in oil. Viscosity and oil flow control in this type of lubrication system have significant impact on bearing losses (and lubrication temperature).
- Heat stabilization of the lubrication system during thrust bearing loss testing.
- Thrust bearings need axial thrust and running time to seat properly, also affecting bearing losses. In mounting vertical motors horizontally, the cooling air flow may not be typical of the vertical mounting.
- A different heating pattern will also affect efficiency, in addition to the more obvious different temperature levels.
- Horizontal mounting may also affect the air gap, also causing an increase in losses.
|
