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

In some instances, operating a motor beyond the bottom pole velocity is feasible and provides system advantages if the design is carefully examined. The pole velocity 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 through 12-pole motors at 50 hertz (Hz [common in Europe]) and 60 Hz (common within the U.S.). As illustrated, additional poles scale back the base pole pace. If the incoming line frequency does not change, the speed of the induction motor shall be less than these values by a percent to slide. So, to operate the motor above the bottom 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 velocity motor with a lower horsepower score and function it above base frequency to get the required torque at a decrease present. This enables the number of a VFD with a lower present rating for use while nonetheless ensuring passable management of the pump/motor over its desired operating vary. The decrease present requirement of the drive can reduce the capital value of the system, relying on total system requirements.
The applications where the motor and the driven pump function above their rated speeds can provide further move and pressure to the managed system. This may result in a more compact system while increasing its efficiency. While it might be potential 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 those purposes is to overlay the pump pace torque curve and motor velocity torque to make sure the motor starts and capabilities throughout the entire operational pace vary with out overheating, stalling or creating any important stresses on the pumping system.
Several factors also must be taken into consideration when considering such solutions:
Noise will improve with pace.
Bearing life or greasing intervals could also be lowered, or improved fit bearings could also be required.
The larger speed (and variable pace in general) will improve the chance of resonant vibration due to a critical velocity within the working range.
The larger velocity will lead to additional power consumption. It is necessary to think about if the pump and drive prepare is rated for the higher power.
Since เกจวัดแรงดันแก๊สlpg required by a rotodynamic pump will increase in proportion to the square of speed, the other main concern is to ensure that the motor can present 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) may be maintained as the frequency utilized to the motor is elevated. Maintaining a relentless V/Hz ratio keeps torque production stable. While it would be best to increase the voltage to the motor as it is run above its rated speed, the voltage of the alternating current (AC) energy supply limits the maximum voltage that is obtainable to the motor. Therefore, the voltage supplied to the motor cannot proceed to extend above the nameplate voltage as illustrated in Image 2. As proven in Image 3, the available torque decreases beyond 100 percent frequency because the V/Hz ratio isn’t maintained. In an overspeed scenario, the load torque (pump) should be beneath the available torque.
Before working any piece of equipment outdoors of its rated speed range, it is important to contact the producer of the tools to determine if this can be done safely and effectively. For more data on variable velocity pumping, check with HI’s “Application Guideline for Variable Speed Pumping” at pumps.org.
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