In some situations, working a motor beyond the bottom pole speed is possible and presents system benefits if the design is rigorously examined. The pole velocity of a motor is a perform 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, extra poles cut back the bottom pole speed. If the incoming line frequency does not change, the speed of the induction motor might be less than these values by a percent to slide. So, to function the motor above the bottom pole velocity, the frequency needs to be increased, which could be done with a variable frequency drive (VFD).
One purpose for overspeeding a motor on a pump is to make use of a slower rated speed motor with a lower horsepower ranking and function it above base frequency to get the required torque at a decrease current. This allows the choice of a VFD with a lower current ranking for use while still ensuring passable control of the pump/motor over its desired operating range. The lower present requirement of the drive can reduce the capital price of the system, depending on general system requirements.
The purposes the place the motor and the driven pump operate above their rated speeds can present further flow and pressure to the managed system. This might end in a extra compact system whereas growing its effectivity. While it may be attainable to increase the motor’s pace to twice its nameplate speed, it’s extra common that the utmost velocity is extra limited.
The key to those purposes is to overlay the pump speed torque curve and motor speed torque to ensure the motor starts and capabilities throughout the complete operational velocity range without overheating, stalling or creating any important stresses on the pumping system.
Several factors also have to be taken under consideration when contemplating such solutions:
Noise will enhance with speed.
Bearing life or greasing intervals could also be reduced, or improved match bearings could also be required.
The higher velocity (and variable pace in general) will improve the chance of resonant vibration as a outcome of a critical velocity inside the working vary.
The larger velocity will result in further energy consumption. pressure gauge 0 10 bar ราคา is important to consider if the pump and drive train is rated for the upper power.
Since the torque required by a rotodynamic pump increases in proportion to the square of pace, the opposite main concern is to guarantee that the motor can present enough torque to drive the load on the increased velocity. When operated at a velocity beneath the rated speed of the motor, the volts per hertz (V/Hz) can be maintained because the frequency applied to the motor is elevated. Maintaining a relentless V/Hz ratio retains torque production secure. While it would be best to extend the voltage to the motor as it’s run above its rated velocity, the voltage of the alternating present (AC) power supply limits the utmost voltage that is out there to the motor. Therefore, the voltage provided to the motor can’t continue to increase above the nameplate voltage as illustrated in Image 2. As shown in Image 3, the available torque decreases past 100% frequency as a outcome of the V/Hz ratio isn’t maintained. In an overspeed scenario, the load torque (pump) must be below the obtainable torque.
Before operating any piece of kit exterior of its rated velocity range, it is essential to contact the producer of the gear to determine if this could be done safely and efficiently. For more information on variable speed pumping, check with HI’s “Application Guideline for Variable Speed Pumping” at pumps.org.
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