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

In some cases, working a motor beyond the bottom pole speed is feasible and presents system benefits if the design is rigorously examined. The pole pace of a motor is a operate of the quantity poles and the incoming line frequency. Image 1 presents the synchronous pole pace for 2-pole via 12-pole motors at 50 hertz (Hz [common in Europe]) and 60 Hz (common within the U.S.). As illustrated, further poles cut back the base pole pace. If the incoming line frequency doesn’t change, the pace of the induction motor will be less than these values by a percent to slip. So, to operate the motor above the bottom pole pace, the frequency must be increased, which may be done with a variable frequency drive (VFD).
One reason for overspeeding a motor on a pump is to use a slower rated pace motor with a decrease horsepower score and operate it above base frequency to get the required torque at a decrease present. This permits the choice of a VFD with a decrease current rating to be used whereas still guaranteeing satisfactory management of the pump/motor over its desired working range. The lower current requirement of the drive can cut back the capital price of the system, relying on general system necessities.
pressure gauge น้ำ and the driven pump function above their rated speeds can provide extra flow and pressure to the controlled system. This might lead to a more compact system whereas increasing its efficiency. While it may be possible to increase the motor’s speed to twice its nameplate speed, it’s extra widespread that the utmost speed is extra restricted.
The key to these functions is to overlay the pump speed torque curve and motor speed torque to ensure the motor begins and features throughout the whole operational pace range with out overheating, stalling or creating any significant stresses on the pumping system.
Several points additionally have to be taken under consideration when contemplating such options:
Noise will increase with velocity.
Bearing life or greasing intervals may be decreased, or improved fit bearings may be required.
The larger velocity (and variable velocity in general) will increase the chance of resonant vibration as a end result of a crucial pace inside the operating range.
The larger velocity will result in extra energy consumption. It is essential to think about if the pump and drive train is rated for the upper energy.
Since the torque required by a rotodynamic pump will increase in proportion to the sq. of velocity, the opposite main concern is to guarantee that the motor can provide sufficient torque to drive the load at the increased velocity. When operated at a velocity below the rated velocity of the motor, the volts per hertz (V/Hz) may be maintained as the frequency utilized to the motor is elevated. Maintaining a continuing V/Hz ratio retains torque manufacturing secure. While it would be perfect to increase the voltage to the motor as it’s run above its rated velocity, the voltage of the alternating present (AC) power source limits the maximum voltage that is obtainable to the motor. Therefore, the voltage provided to the motor can not proceed to extend above the nameplate voltage as illustrated in Image 2. As proven in Image three, the available torque decreases beyond 100 percent frequency as a end result of the V/Hz ratio just isn’t maintained. In an overspeed state of affairs, the load torque (pump) should be under the available torque.
Before working any piece of kit outdoors of its rated velocity vary, it’s important to contact the producer of the equipment to find out if this can be accomplished safely and efficiently. For more data on variable velocity pumping, check with HI’s “Application Guideline for Variable Speed Pumping” at

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