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

In some cases, working a motor past the base pole pace is possible and offers system benefits if the design is fastidiously examined. The pole velocity of a motor is a operate of the quantity poles and the incoming line frequency. เกจวัดแรงดันไฟฟ้า presents the synchronous pole velocity for 2-pole via 12-pole motors at 50 hertz (Hz [common in Europe]) and 60 Hz (common within the U.S.). As illustrated, additional poles cut back the base pole pace. If the incoming line frequency does not change, the speed of the induction motor shall be less than these values by a p.c to slide. So, to function the motor above the bottom pole speed, the frequency must be elevated, which may be accomplished 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 decrease horsepower score and function it above base frequency to get the required torque at a lower current. This enables the number of a VFD with a lower current rating to be used while nonetheless making certain satisfactory management of the pump/motor over its desired operating range. The lower current requirement of the drive can scale back the capital value of the system, relying on overall system requirements.
The functions the place the motor and the driven pump operate above their rated speeds can present further circulate and pressure to the controlled system. This may lead to a extra compact system whereas increasing its effectivity. While it could be attainable to increase the motor’s speed to twice its nameplate velocity, it’s extra widespread that the maximum pace is more limited.
The key to those applications is to overlay the pump velocity torque curve and motor speed torque to make sure the motor starts and functions throughout the whole operational speed range with out overheating, stalling or creating any important stresses on the pumping system.
Several points also need to be taken under consideration when contemplating such options:
Noise will enhance with velocity.
Bearing life or greasing intervals may be decreased, or improved fit bearings may be required.
The higher pace (and variable pace in general) will improve the chance of resonant vibration as a result of a crucial velocity throughout the working range.
The larger speed will lead to extra power consumption. It is important to consider if the pump and drive train is rated for the higher energy.
Since the torque required by a rotodynamic pump will increase in proportion to the sq. of velocity, the opposite main concern is to make sure that the motor can present sufficient torque to drive the load on the increased speed. When operated at a velocity beneath the rated pace of the motor, the volts per hertz (V/Hz) could be maintained as the frequency utilized to the motor is elevated. Maintaining a constant V/Hz ratio retains torque production steady. While it might be ideal to increase the voltage to the motor as it is run above its rated velocity, the voltage of the alternating current (AC) power supply limits the utmost voltage that is obtainable to the motor. Therefore, the voltage provided to the motor can’t continue to extend above the nameplate voltage as illustrated in Image 2. As shown in Image three, the obtainable torque decreases past one hundred pc frequency as a outcome of the V/Hz ratio is not maintained. In an overspeed scenario, the load torque (pump) should be beneath the out there torque.
Before working any piece of kit outside of its rated velocity vary, it is essential to contact the manufacturer of the tools to find out if this might be carried out safely and effectively. For more information on variable velocity pumping, check with HI’s “Application Guideline for Variable Speed Pumping” at

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