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In ไดอะแฟรม ซีล , working a motor beyond the bottom pole velocity is possible and offers system benefits if the design is fastidiously examined. ไดอะแฟรม of a motor is a function of the quantity poles and the incoming line frequency. Image 1 presents the synchronous pole pace for 2-pole via 12-pole motors at 50 hertz (Hz [common in Europe]) and 60 Hz (common in the U.S.). As illustrated, further poles cut back the base pole velocity. If the incoming line frequency does not change, the pace of the induction motor will be less than these values by a percent to slip. So, to operate the motor above the bottom pole velocity, the frequency must be elevated, which could be done with a variable frequency drive (VFD).
One reason 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 present. This enables the choice of a VFD with a lower present ranking to be used whereas still guaranteeing satisfactory control of the pump/motor over its desired operating vary. The decrease present requirement of the drive can reduce the capital price of the system, relying on total system requirements.
เกจวัดแรงดัน and the driven pump operate above their rated speeds can present extra flow and stress to the managed system. This may end in a more compact system while rising its efficiency. While it may be attainable to extend the motor’s speed to twice its nameplate pace, it is extra common that the utmost velocity is more limited.
The key to these applications is to overlay the pump pace torque curve and motor speed torque to make sure the motor starts and functions throughout the complete operational speed range without overheating, stalling or creating any vital stresses on the pumping system.
Several points additionally must be taken under consideration when contemplating such solutions:
Noise will increase with speed.
Bearing life or greasing intervals could additionally be reduced, or improved match bearings may be required.
The higher pace (and variable velocity in general) will increase the chance of resonant vibration as a result of a crucial speed within the working vary.
The greater velocity will result in further power consumption. It is necessary to suppose about if the pump and drive prepare 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 ensure that the motor can present sufficient torque to drive the load on the elevated pace. When operated at a speed below the rated velocity of the motor, the volts per hertz (V/Hz) could be maintained as the frequency applied to the motor is increased. Maintaining a relentless V/Hz ratio retains torque production secure. While it would 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 utmost voltage that is obtainable to the motor. Therefore, the voltage provided to the motor can’t proceed to increase above the nameplate voltage as illustrated in Image 2. As shown in Image three, the out there torque decreases past 100 percent frequency as a end result of the V/Hz ratio isn’t maintained. In an overspeed situation, the load torque (pump) have to be beneath the out there torque.
Before operating any piece of equipment exterior of its rated speed vary, it is essential to contact the manufacturer of the tools to determine if this may be done safely and effectively. For more information on variable velocity pumping, discuss with HI’s “Application Guideline for Variable Speed Pumping” at pumps.org.
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