In Which Applications Can a Pump Motor Be Operated Above Base Speed?

In some cases, operating a motor beyond the base pole pace is possible and offers system advantages if the design is rigorously examined. The pole velocity of a motor is a function of the number poles and the incoming line frequency. Image 1 presents the synchronous pole velocity for 2-pole through 12-pole motors at 50 hertz (Hz [common in Europe]) and 60 Hz (common in the U.S.). As illustrated, extra poles scale back the bottom pole pace. If the incoming line frequency doesn’t change, the velocity of the induction motor shall be lower than these values by a p.c to slide. So, to function the motor above the bottom pole speed, the frequency needs to be elevated, which can be carried out with a variable frequency drive (VFD).
One cause for overspeeding a motor on a pump is to make use of a slower rated velocity motor with a lower horsepower ranking and function it above base frequency to get the required torque at a lower present. This permits the selection of a VFD with a decrease current score to be used while still making certain passable control of the pump/motor over its desired operating range. The lower current requirement of the drive can reduce the capital price of the system, depending on total system necessities.
The functions where the motor and the driven pump operate above their rated speeds can present additional flow and pressure to the managed system. This may lead to a extra compact system whereas growing its efficiency. While it could be possible to extend the motor’s speed to twice its nameplate speed, it is extra widespread that the utmost pace is more limited.
The key to those applications is to overlay the pump velocity torque curve and motor pace torque to ensure the motor starts and functions throughout the entire operational velocity range with out overheating, stalling or creating any important stresses on the pumping system.
เกจวัดแรงดัน4บาร์ have to be taken under consideration when contemplating such solutions:
Noise will improve with velocity.
Bearing life or greasing intervals could additionally be reduced, or improved match bearings may be required.
The greater pace (and variable speed in general) will improve the chance of resonant vibration due to a important velocity throughout the working vary.
The larger speed will result in extra power consumption. It is essential to suppose about if the pump and drive prepare is rated for the upper power.
Since the torque required by a rotodynamic pump will increase in proportion to the square of pace, the other major concern is to make sure that the motor can provide enough torque to drive the load on the increased velocity. When operated at a velocity under the rated speed of the motor, the volts per hertz (V/Hz) can be maintained as the frequency applied to the motor is elevated. Maintaining a relentless V/Hz ratio keeps torque production stable. While it would be best to increase the voltage to the motor as it is run above its rated speed, the voltage of the alternating present (AC) energy supply limits the maximum voltage that is out there to the motor. Therefore, the voltage supplied to the motor can not proceed to increase above the nameplate voltage as illustrated in Image 2. As shown in Image 3, the available torque decreases beyond one hundred pc frequency as a result of the V/Hz ratio just isn’t maintained. In an overspeed state of affairs, the load torque (pump) should be beneath the available torque.
Before working any piece of apparatus outside of its rated speed vary, it’s essential to contact the manufacturer of the equipment to determine if this can be done safely and effectively. For extra info on variable pace pumping, refer to HI’s “Application Guideline for Variable Speed Pumping” at pumps.org.
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