Circulation and Heat Exchanger Motors
All SME motors except 6″, 8″, and 10″ 4P motors have internal water circulation as standard. The internal water is “force” circulated by an impeller inside the motor. Circulating the water distributes the heat inside the motor more evenly and reduces the maximum temperatures in the active part of the motor especially the windings. Typically this reduces the winding temperature inside the motor by 10 Deg.C.
All SME motors except 6″ can be offered with a Heat Exchanger which increases the surface area that is exposed to the external water by 50%. The internal water is also “force” circulated inside the motor and through the Heat Exchanger. The water exiting the Heat Exchanger is almost back to the ambient water temperature before it recirculates through the motor again. These motors can reduce the temperature rise inside the motor to just l2 Deg.C. which allows SME to offer these motors for high ambient water temperatures – typically up to 60 Deg.C. ambient in some applications. There are plenty of SME Heat Exchanger motors operating successfully in ambient waters above 50 Deg.C. In 30 Deg.C. ambient water the winding temperature on full load will be about 45 Deg.C. (15 Deg.C. temperature rise).
Because these motors have a signiﬁcantly lower operating temperature compared to a standard motor, the efﬁciency is better, due to lower stator and rotor copper losses, and the full load speed is higher. The internal water circulation impeller has a negligible effect on the efficiency. The lower operating temperature will increase the “life” of the motor.
The “rule of thumb” for electrical insulation is that “The life is shortened by 50% for every 10 Deg.C. of operating temperature”. On this basis the motors with circulation will have double the life of a motor with no circulation and the motors with a Heat Exchanger and circulation will have 3 to 4 times the life.
Summary of the Advantages:
- Extended Life for the windings and the motor.
- Higher allowable Ambient water temperatures.
- Higher power from smaller diameter wells.
- Suitable for High or Low ﬂow wells.
- May be suitable for use in Cascading wells without a Shroud.
- May be suitable for use in wells with iron bacteria.