In some cases, operating a motor beyond the bottom pole pace is feasible and presents system advantages if the design is rigorously examined. The pole pace 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 through 12-pole motors at 50 hertz (Hz [common in Europe]) and 60 Hz (common within the U.S.). As illustrated, extra poles scale back the bottom pole velocity. If the incoming line frequency does not change, the pace of the induction motor shall be lower than these values by a percent to slip. So, to function the motor above the bottom pole speed, the frequency needs to be elevated, which may be accomplished with a variable frequency drive (VFD).
One reason for overspeeding a motor on a pump is to use a slower rated speed motor with a lower horsepower score and operate it above base frequency to get the required torque at a decrease present. This allows the number of a VFD with a lower present ranking to be used whereas nonetheless guaranteeing passable control 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 overall system requirements.
เกจวัดแรงดัน and the pushed pump function above their rated speeds can present further move and stress to the managed system. This may result in a more compact system while growing its effectivity. While it could be possible to extend the motor’s pace to twice its nameplate pace, it is more common that the utmost velocity is extra limited.
The key to those purposes is to overlay the pump pace torque curve and motor speed torque to ensure the motor starts and capabilities throughout the entire operational pace range without overheating, stalling or creating any vital stresses on the pumping system.
Several factors also must be taken into account when contemplating such options:
Noise will increase with pace.
Bearing life or greasing intervals may be lowered, or improved match bearings could additionally be required.
The greater pace (and variable pace in general) will increase the chance of resonant vibration because of a crucial pace throughout the working range.
ไดอะแฟรม ซีล will end in extra power consumption. It is necessary to contemplate if the pump and drive practice is rated for the upper energy.
Since the torque required by a rotodynamic pump will increase in proportion to the sq. of pace, the other major concern is to ensure that the motor can provide sufficient torque to drive the load at the elevated pace. When operated at a speed beneath the rated pace of the motor, the volts per hertz (V/Hz) may be maintained as the frequency utilized to the motor is increased. Maintaining a continuing V/Hz ratio keeps torque manufacturing stable. While it will be perfect to extend the voltage to the motor as it is run above its rated velocity, the voltage of the alternating current (AC) power source limits the utmost voltage that is available to the motor. Therefore, the voltage provided to the motor can’t continue to extend above the nameplate voltage as illustrated in Image 2. As proven in Image 3, the available torque decreases beyond 100% frequency because the V/Hz ratio isn’t maintained. In an overspeed situation, the load torque (pump) should be under the out there torque.
Before operating any piece of apparatus outdoors of its rated velocity range, it is essential to contact the manufacturer of the tools to determine if this may be carried out safely and effectively. For more information on variable velocity pumping, refer to HI’s “Application Guideline for Variable Speed Pumping” at pumps.org.
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