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

In some cases, operating a motor beyond the bottom pole velocity is feasible and offers system benefits if the design is carefully examined. The pole velocity of a motor is a perform of the number poles and the incoming line frequency. Image 1 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, further poles reduce the base pole velocity. If the incoming line frequency doesn’t change, the velocity of the induction motor might be lower than these values by a percent to slip. So, to operate เกจวัดแรงดัน above the base 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 operate it above base frequency to get the required torque at a lower present. This allows the number of a VFD with a decrease current rating for use while still making certain satisfactory management of the pump/motor over its desired working vary. The lower present requirement of the drive can reduce the capital price of the system, depending on total system necessities.
The applications where the motor and the driven pump function above their rated speeds can present extra circulate and strain to the controlled system. This may end in 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 velocity is extra limited.
The key to those purposes is to overlay the pump velocity torque curve and motor speed torque to make sure the motor begins and features all through the complete operational velocity range with out overheating, stalling or creating any vital stresses on the pumping system.
Several points also must be taken into consideration when contemplating such solutions:
Noise will increase with velocity.
Bearing life or greasing intervals could also be reduced, or improved fit bearings may be required.
The higher speed (and variable velocity in general) will enhance the danger of resonant vibration due to a important speed throughout the working vary.
The greater velocity will lead to additional 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 square of velocity, the other main concern is to make sure that the motor can present enough torque to drive the load at the increased pace. When operated at a speed under the rated velocity of the motor, the volts per hertz (V/Hz) can be maintained as the frequency applied to the motor is increased. Maintaining a constant V/Hz ratio retains torque production secure. While it might be perfect to extend the voltage to the motor as it’s run above its rated velocity, the voltage of the alternating current (AC) power supply limits the maximum voltage that’s available to the motor. Therefore, the voltage equipped to the motor cannot continue to increase above the nameplate voltage as illustrated in Image 2. As shown in Image three, the out there torque decreases beyond 100% frequency because the V/Hz ratio isn’t maintained. In an overspeed situation, the load torque (pump) have to be below the obtainable torque.
Before operating any piece of equipment exterior of its rated pace range, it is important to contact the producer of the gear to determine if this may be accomplished safely and effectively. For extra information on variable velocity pumping, discuss with HI’s “Application Guideline for Variable Speed Pumping” at pumps.org.
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