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

In some cases, operating a motor beyond the bottom pole velocity is feasible and presents system advantages if the design is fastidiously examined. The pole speed of a motor is a function of the number 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, extra poles reduce the base pole velocity. If the incoming line frequency doesn’t change, the speed of the induction motor will be less than these values by a percent to slip. So, to function the motor above the bottom pole speed, the frequency must be increased, which could be carried out with a variable frequency drive (VFD).
เกจไนโตรเจนsumo for overspeeding a motor on a pump is to use a slower rated speed motor with a decrease horsepower ranking and operate it above base frequency to get the required torque at a lower present. This enables the selection of a VFD with a decrease current score for use whereas still making certain passable control of the pump/motor over its desired operating range. The decrease current requirement of the drive can scale back the capital price of the system, depending on total system necessities.
The purposes the place the motor and the pushed pump operate above their rated speeds can present further flow and strain to the controlled system. This could result in a extra compact system whereas growing its efficiency. While it could be attainable to increase the motor’s speed to twice its nameplate pace, it’s more common that the maximum speed is extra limited.
The key to these functions is to overlay the pump speed torque curve and motor velocity torque to make sure the motor starts and capabilities throughout the entire operational velocity range without overheating, stalling or creating any vital stresses on the pumping system.
Several factors also have to be taken under consideration when considering such options:
Noise will improve with velocity.
Bearing life or greasing intervals may be lowered, or improved fit bearings could also be required.
The higher pace (and variable speed in general) will increase the danger of resonant vibration because of a critical velocity inside the working vary.
The greater velocity will end in further power consumption. It is important to consider if the pump and drive prepare is rated for the higher energy.
Since the torque required by a rotodynamic pump will increase in proportion to the square of speed, the opposite main concern is to ensure that the motor can provide sufficient torque to drive the load at the increased pace. When operated at a velocity under the rated pace of the motor, the volts per hertz (V/Hz) can be maintained as the frequency utilized to the motor is increased. Maintaining a relentless V/Hz ratio keeps torque manufacturing stable. While it will be best to extend the voltage to the motor as it is run above its rated pace, the voltage of the alternating present (AC) power source limits the utmost voltage that’s available to the motor. Therefore, the voltage equipped to the motor can not proceed to extend above the nameplate voltage as illustrated in Image 2. As proven in Image three, the available torque decreases past 100 percent frequency as a result of the V/Hz ratio just isn’t maintained. In an overspeed scenario, the load torque (pump) should be under the obtainable torque.
Before operating any piece of apparatus outdoors of its rated pace vary, it is important to contact the producer of the gear to discover out if this can be accomplished safely and efficiently. For more information on variable velocity pumping, refer to HI’s “Application Guideline for Variable Speed Pumping” at pumps.org.
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