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

In some instances, working a motor beyond the base pole velocity is feasible and presents system advantages if the design is carefully examined. The pole speed of a motor is a operate of the number poles and the incoming line frequency. digital pressure gauge 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 base pole velocity. If the incoming line frequency doesn’t change, the speed of the induction motor shall be lower than these values by a p.c to slide. So, to function the motor above the base pole speed, the frequency must be increased, which may be accomplished with a variable frequency drive (VFD).
One reason for overspeeding a motor on a pump is to make use of a slower rated pace motor with a lower horsepower ranking and function it above base frequency to get the required torque at a lower current. This enables the choice of a VFD with a lower current score for use while still making certain passable control of the pump/motor over its desired operating range. The decrease current requirement of the drive can reduce the capital value of the system, relying on total system requirements.
The purposes the place the motor and the driven pump operate above their rated speeds can provide further circulate and pressure to the controlled system. This could end in a extra compact system whereas rising its efficiency. While digital pressure gauge may be attainable to extend the motor’s velocity to twice its nameplate velocity, it’s extra widespread that the utmost speed is extra limited.
The key to those functions is to overlay the pump velocity torque curve and motor speed torque to ensure the motor begins and capabilities all through the whole operational velocity vary with out overheating, stalling or creating any important stresses on the pumping system.
Several factors also have to be taken under consideration when considering such options:
Noise will enhance with speed.
Bearing life or greasing intervals may be reduced, or improved match bearings may be required.
เพรสเชอร์เกจ (and variable speed in general) will enhance the danger of resonant vibration due to a crucial pace throughout the operating vary.
The greater velocity will end in additional power consumption. It is important to contemplate if the pump and drive practice is rated for the higher power.
Since the torque required by a rotodynamic pump increases in proportion to the sq. of velocity, the opposite major concern is to guarantee that the motor can present sufficient torque to drive the load on the increased speed. When operated at a velocity beneath the rated speed of the motor, the volts per hertz (V/Hz) may be maintained because the frequency utilized to the motor is elevated. Maintaining a relentless V/Hz ratio keeps torque manufacturing secure. While it would be perfect 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 utmost voltage that is available to the motor. Therefore, the voltage supplied to the motor cannot continue to increase above the nameplate voltage as illustrated in Image 2. As shown in Image three, the obtainable torque decreases beyond 100% frequency as a outcome of the V/Hz ratio is not maintained. In an overspeed situation, the load torque (pump) have to be beneath the out there torque.
Before operating any piece of kit outside of its rated velocity vary, it’s important to contact the manufacturer of the gear to find out if this can be done safely and effectively. For more information on variable speed pumping, discuss with HI’s “Application Guideline for Variable Speed Pumping” at pumps.org.
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