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

In เกจวัดน้ำยาแอร์refco , operating a motor past the bottom pole speed is feasible and presents system advantages 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 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, further poles reduce the base pole pace. If the incoming line frequency doesn’t change, the velocity of the induction motor shall be less than these values by a p.c to slide. So, to function the motor above the bottom pole pace, the frequency needs to be elevated, which may be accomplished with a variable frequency drive (VFD).
One purpose for overspeeding a motor on a pump is to use a slower rated pace motor with a lower horsepower rating and operate it above base frequency to get the required torque at a lower current. This enables the number of a VFD with a decrease current rating to be used while nonetheless ensuring passable 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 necessities.
The functions the place the motor and the pushed pump function above their rated speeds can provide further move and strain to the controlled system. This might end in a more compact system whereas increasing its effectivity. While it might be potential to increase the motor’s velocity to twice its nameplate pace, it is more frequent that the maximum pace is extra restricted.
The key to those functions is to overlay the pump pace torque curve and motor speed torque to make sure the motor starts and capabilities all through the complete operational speed vary without overheating, stalling or creating any important stresses on the pumping system.
Several points additionally have to be taken into consideration when considering such solutions:
Noise will increase with speed.
Bearing life or greasing intervals may be lowered, or improved fit bearings could also be required.
The higher pace (and variable velocity in general) will increase the risk of resonant vibration because of a crucial velocity within the operating vary.
The higher velocity will end in further power consumption. It is essential 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 square of pace, the other major concern is to make sure that the motor can present sufficient torque to drive the load on the elevated velocity. When operated at a pace beneath the rated speed of the motor, the volts per hertz (V/Hz) may be maintained as the frequency applied to the motor is elevated. Maintaining a continuing V/Hz ratio retains torque manufacturing stable. While it would be ideal to extend the voltage to the motor as it’s run above its rated velocity, the voltage of the alternating present (AC) power supply limits the maximum voltage that’s out there to the motor. Therefore, the voltage supplied to the motor cannot continue to extend above the nameplate voltage as illustrated in Image 2. As proven in Image 3, the available torque decreases past 100 percent frequency because the V/Hz ratio just isn’t maintained. In an overspeed state of affairs, the load torque (pump) should be beneath the available torque.
Before working any piece of apparatus outdoors of its rated speed vary, it is important to contact the manufacturer of the gear to discover out if this can be accomplished safely and efficiently. For more information on variable speed pumping, discuss with HI’s “Application Guideline for Variable Speed Pumping” at pumps.org.
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