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In some instances, operating a motor past the bottom pole pace is feasible and provides system advantages if the design is fastidiously examined. The pole velocity of a motor is a operate of the quantity poles and the incoming line frequency. เครื่องมือใช้วัดความดัน 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 in the U.S.). As illustrated, additional poles scale back the base pole speed. If the incoming line frequency doesn’t change, the velocity of the induction motor shall be less than these values by a % to slide. So, to operate the motor above the bottom pole speed, the frequency needs to be elevated, which can be carried out 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 rating and operate it above base frequency to get the required torque at a lower present. This permits the selection of a VFD with a decrease present rating for use while still ensuring passable management of the pump/motor over its desired working range. The decrease present requirement of the drive can cut back the capital cost of the system, depending on general system requirements.
The functions where the motor and the driven pump function above their rated speeds can present additional circulate and pressure to the controlled system. This may lead to a more compact system whereas growing its efficiency. While it could be attainable to increase the motor’s pace to twice its nameplate pace, it is more frequent that the maximum speed is extra restricted.
The key to these purposes is to overlay the pump velocity torque curve and motor velocity torque to ensure the motor starts and functions all through the entire operational pace range without overheating, stalling or creating any significant stresses on the pumping system.
Several points also must be taken into consideration when contemplating such options:
Noise will improve with velocity.
Bearing life or greasing intervals could also be decreased, or improved match bearings may be required.
The larger speed (and variable speed in general) will improve the danger of resonant vibration due to a crucial speed within the operating range.
The higher velocity will lead to extra power consumption. It is essential to assume about if the pump and drive practice is rated for the higher energy.
Since the torque required by a rotodynamic pump will increase in proportion to the sq. of velocity, the other main concern is to make sure that the motor can provide enough torque to drive the load on the elevated velocity. When operated at a speed under the rated speed of the motor, the volts per hertz (V/Hz) could be maintained because the frequency applied to the motor is elevated. Maintaining a continuing V/Hz ratio keeps torque production stable. While it would be perfect to extend the voltage to the motor as it is run above its rated velocity, the voltage of the alternating current (AC) energy supply limits the utmost voltage that is available to the motor. Therefore, the voltage equipped to the motor can’t proceed to increase above the nameplate voltage as illustrated in Image 2. As proven in Image 3, the out there torque decreases past one hundred pc frequency because the V/Hz ratio isn’t maintained. In an overspeed situation, the load torque (pump) have to be beneath the obtainable torque.
Before operating any piece of kit exterior of its rated velocity vary, it is important to contact the producer of the gear to determine if this might be done safely and effectively. For extra info on variable pace pumping, refer to HI’s “Application Guideline for Variable Speed Pumping” at pumps.org.
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