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

In some situations, operating a motor past the base pole pace is possible and provides system advantages if the design is carefully examined. The pole speed of a motor is a operate of the quantity poles and the incoming line frequency. Image 1 presents the synchronous pole velocity for 2-pole through 12-pole motors at 50 hertz (Hz [common in Europe]) and 60 Hz (common within the U.S.). As illustrated, further poles cut back the bottom pole pace. If the incoming line frequency does not change, the pace of the induction motor will be lower than these values by a p.c to slide. So, to operate the motor above the bottom pole speed, the frequency needs to be increased, which can be accomplished with a variable frequency drive (VFD).
One purpose for overspeeding a motor on a pump is to use a slower rated velocity motor with a decrease horsepower rating and operate it above base frequency to get the required torque at a decrease present. This allows the selection of a VFD with a lower current score to be used while nonetheless ensuring passable management of the pump/motor over its desired working range. The lower current requirement of the drive can reduce the capital price of the system, relying on overall system requirements.
The functions the place the motor and the pushed pump function above their rated speeds can present additional flow and stress to the managed system. This may end in a extra compact system while growing its efficiency. While it may be attainable to extend the motor’s speed to twice its nameplate speed, it is extra frequent that the maximum pace is extra limited.
เกจวัดแก๊สหุงต้ม to those applications is to overlay the pump pace torque curve and motor pace torque to ensure the motor starts and features all through the whole operational speed range without overheating, stalling or creating any important stresses on the pumping system.
Several factors additionally have to be taken into account when contemplating such options:
Noise will increase with velocity.
Bearing compound gauge ราคา or greasing intervals may be reduced, or improved fit bearings could additionally be required.
The higher speed (and variable velocity in general) will improve the risk of resonant vibration because of a critical pace throughout the operating vary.
The higher speed will end in further energy consumption. It is necessary to contemplate if the pump and drive prepare is rated for the higher power.
Since the torque required by a rotodynamic pump increases in proportion to the square of velocity, the opposite main concern is to ensure that the motor can present enough torque to drive the load on the increased speed. When operated at a speed below the rated speed of the motor, the volts per hertz (V/Hz) could be maintained as the frequency applied to the motor is increased. Maintaining a continuing V/Hz ratio keeps torque manufacturing stable. While it might be best to increase the voltage to the motor as it’s run above its rated speed, the voltage of the alternating present (AC) energy source limits the maximum voltage that’s obtainable to the motor. Therefore, the voltage provided to the motor cannot proceed to extend above the nameplate voltage as illustrated in Image 2. As proven in Image 3, the available 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 below the available torque.
Before operating any piece of apparatus outdoors of its rated pace vary, it is important to contact the producer of the equipment to discover out if this could be accomplished safely and efficiently. For more info on variable speed pumping, refer to HI’s “Application Guideline for Variable Speed Pumping” at pumps.org.
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