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

In some situations, working a motor beyond the base pole velocity is possible and presents system advantages if the design is fastidiously examined. The pole speed of a motor is a perform of the number poles and the incoming line frequency. Image 1 presents the synchronous pole pace for 2-pole by way of 12-pole motors at 50 hertz (Hz [common in Europe]) and 60 Hz (common within the U.S.). As illustrated, extra poles reduce the bottom pole velocity. If the incoming line frequency does not change, the velocity of the induction motor shall be lower than these values by a % to slide. So, to function the motor above the base pole velocity, the frequency needs to be elevated, which can be accomplished with a variable frequency drive (VFD).
One reason for overspeeding a motor on a pump is to use a slower rated velocity motor with a lower horsepower rating and function it above base frequency to get the required torque at a lower present. This enables the number of a VFD with a lower present score for use whereas still making certain satisfactory control of the pump/motor over its desired operating range. The lower current requirement of the drive can cut back the capital value of the system, depending on total system requirements.
The applications where the motor and the driven pump operate above their rated speeds can present further circulate and stress to the controlled system. This may lead to a extra compact system while increasing its efficiency. While เพรสเชอร์เกจ may be attainable to increase the motor’s speed to twice its nameplate pace, it is more frequent that the utmost pace is more limited.
The key to these applications is to overlay the pump velocity torque curve and motor speed torque to ensure the motor begins and features throughout the whole operational speed range with out overheating, stalling or creating any significant stresses on the pumping system.
Several points also need to be taken into consideration when considering such options:
Noise will enhance with pace.
Bearing life or greasing intervals could additionally be decreased, or improved match bearings may be required.
The higher speed (and variable velocity in general) will improve the chance of resonant vibration due to a important pace throughout the working vary.
The greater speed will end in further power consumption. It is essential to contemplate if the pump and drive prepare is rated for the higher power.
Since the torque required by a rotodynamic pump will increase in proportion to the square of speed, the opposite main concern is to ensure that the motor can present sufficient torque to drive the load at the increased pace. When operated at a velocity beneath the rated pace of the motor, the volts per hertz (V/Hz) may be maintained because the frequency applied to the motor is increased. Maintaining a constant V/Hz ratio retains torque manufacturing steady. While it will be best to extend the voltage to the motor as it’s run above its rated velocity, the voltage of the alternating current (AC) power source limits the utmost voltage that is out there to the motor. Therefore, the voltage provided to the motor cannot proceed to extend above the nameplate voltage as illustrated in Image 2. As proven in Image 3, the out there torque decreases past one hundred pc frequency as a outcome of the V/Hz ratio isn’t maintained. In an overspeed state of affairs, the load torque (pump) have to be under the available torque.
Before operating any piece of equipment outdoors of its rated speed range, it’s important to contact the producer of the gear to find out if this may be carried out safely and efficiently. For more info on variable pace pumping, refer to HI’s “Application Guideline for Variable Speed Pumping” at

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