In some situations, working a motor past the base pole speed is feasible and presents system benefits if the design is rigorously examined. The pole pace of a motor is a operate of the number poles and the incoming line frequency. Image 1 presents the synchronous pole speed 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, additional poles reduce the base pole pace. If the incoming line frequency doesn’t change, the speed of the induction motor shall be less than these values by a percent to slip. So, to operate the motor above the base pole velocity, the frequency must be elevated, which may be done with a variable frequency drive (VFD).
One purpose for overspeeding a motor on a pump is to use a slower rated speed motor with a lower horsepower ranking and operate it above base frequency to get the required torque at a lower current. This permits the selection of a VFD with a lower present ranking for use whereas still guaranteeing passable management of the pump/motor over its desired operating range. The lower current requirement of the drive can cut back the capital price of the system, depending on total system requirements.
The purposes the place the motor and the pushed pump operate above their rated speeds can provide additional flow and pressure to the controlled system. This might result in a more compact system while growing its effectivity. While it may be potential to increase the motor’s pace to twice its nameplate speed, it’s extra common that the utmost speed is more limited.
The key to these functions is to overlay the pump pace torque curve and motor velocity torque to ensure the motor begins and features all through the entire operational speed vary without overheating, stalling or creating any important stresses on the pumping system.
Several factors also have to be taken under consideration when contemplating such options:
Noise will improve with velocity.
Bearing life or greasing intervals could also be reduced, or improved match bearings may be required.
The higher speed (and variable speed in general) will improve the risk of resonant vibration due to a important speed within the operating range.
The larger speed will end in additional energy consumption. It is important to think about if the pump and drive train is rated for the upper energy.
Since the torque required by a rotodynamic pump increases in proportion to the sq. of pace, the other major concern is to guarantee that the motor can present enough torque to drive the load on the increased speed. When operated at a velocity under the rated velocity of the motor, the volts per hertz (V/Hz) can be maintained because the frequency utilized to the motor is elevated. Maintaining a continuing V/Hz ratio retains torque production stable. While it would be perfect to increase the voltage to the motor as it is run above its rated pace, the voltage of the alternating current (AC) power supply limits the maximum voltage that is available to the motor. Therefore, the voltage equipped to the motor can not continue to increase above the nameplate voltage as illustrated in Image 2. As proven in Image three, the out there torque decreases past 100% frequency because the V/Hz ratio is not maintained. In an overspeed state of affairs, the load torque (pump) must be below the available torque.
Before working เกจวัดแก๊ส of kit outdoors of its rated speed vary, it’s important to contact the producer of the tools to find out if this may be accomplished safely and effectively. For more information on variable speed pumping, check with HI’s “Application Guideline for Variable Speed Pumping” at