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

In some situations, operating a motor beyond the bottom pole pace is possible and provides system benefits if the design is fastidiously examined. The pole pace of a motor is a function of the quantity 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, เกจวัดแรงดันน้ำประปา reduce the bottom pole velocity. If the incoming line frequency doesn’t change, the pace of the induction motor might be less than these values by a % to slide. So, to function the motor above the bottom pole speed, the frequency needs to be increased, which could be accomplished with a variable frequency drive (VFD).
One purpose 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 decrease current. This enables the number of a VFD with a decrease current score to be used while still making certain satisfactory control of the pump/motor over its desired operating vary. The decrease present requirement of the drive can scale back the capital value of the system, depending on overall system requirements.
The purposes where the motor and the pushed pump operate above their rated speeds can provide additional flow and pressure to the controlled system. This may end in a extra compact system whereas increasing its efficiency. While it could be potential to extend the motor’s velocity to twice its nameplate speed, it is extra frequent that the utmost velocity is more limited.
The key to those purposes is to overlay the pump pace torque curve and motor velocity torque to ensure the motor starts and features throughout the entire operational pace range without overheating, stalling or creating any significant stresses on the pumping system.
Several factors also must be taken into consideration when contemplating such solutions:
Noise will enhance with pace.
Bearing life or greasing intervals could also be lowered, or improved match bearings may be required.
The larger pace (and variable velocity in general) will enhance the danger of resonant vibration due to a important pace inside the working range.
The higher pace will end in further power consumption. It is important to contemplate if the pump and drive practice is rated for the upper power.
Since the torque required by a rotodynamic pump increases in proportion to the square of pace, the other major concern is to guarantee that the motor can present enough torque to drive the load at the elevated pace. When operated at a velocity beneath the rated velocity of the motor, the volts per hertz (V/Hz) could be maintained as the frequency applied to the motor is increased. Maintaining a constant V/Hz ratio retains torque manufacturing stable. 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) energy source limits the maximum voltage that is obtainable to the motor. Therefore, the voltage provided to the motor can not continue to increase above the nameplate voltage as illustrated in Image 2. As proven in Image 3, the available torque decreases beyond 100% frequency as a result of the V/Hz ratio isn’t maintained. In an overspeed situation, the load torque (pump) have to be beneath the available torque.
Before working any piece of kit outdoors of its rated velocity vary, it’s essential to contact the manufacturer of the tools to determine if this might be carried out safely and efficiently. For more data on variable speed pumping, refer to HI’s “Application Guideline for Variable Speed Pumping” at pumps.org.
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