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

In some cases, operating a motor beyond the bottom pole velocity is possible and presents system benefits if the design is rigorously examined. The pole velocity of a motor is a perform of the quantity poles and the incoming line frequency. Image 1 presents the synchronous pole velocity for 2-pole through 12-pole motors at 50 hertz (Hz [common in Europe]) and 60 Hz (common in the U.S.). As illustrated, further poles scale back the base pole pace. If the incoming line frequency does not change, the pace of the induction motor will be lower than these values by a % to slide. So, to function the motor above the bottom pole velocity, the frequency must be increased, which could be carried out with a variable frequency drive (VFD).
One cause for overspeeding a motor on a pump is to use a slower rated speed motor with a lower horsepower ranking and operate it above base frequency to get the required torque at a decrease present. This allows the number of a VFD with a decrease current score to be used whereas still ensuring passable management of the pump/motor over its desired working range. The decrease present requirement of the drive can scale back the capital cost of the system, depending on total system necessities.
The functions where the motor and the pushed pump function above their rated speeds can provide further circulate and pressure to the managed system. This may lead to a more compact system while rising its effectivity. While it might be potential to increase the motor’s pace to twice its nameplate speed, it’s more frequent that the utmost speed is more restricted.
The key to these purposes is to overlay the pump speed torque curve and motor speed torque to ensure the motor starts and functions all through the complete operational speed range without overheating, stalling or creating any significant stresses on the pumping system.
Several factors also must be taken into consideration when considering such solutions:
Noise will increase with pace.
Bearing life or greasing intervals could also be lowered, or improved fit bearings may be required.
The higher speed (and variable pace in general) will enhance the chance of resonant vibration due to a critical pace within the working range.
The larger pace will result in additional power consumption. It is necessary to think about if the pump and drive prepare is rated for the upper power.
Since the torque required by a rotodynamic pump increases in proportion to the sq. of velocity, the opposite major concern is to make certain that the motor can present enough torque to drive the load on the elevated pace. When operated at a speed under the rated pace of the motor, the volts per hertz (V/Hz) can be maintained because the frequency utilized to the motor is increased. Maintaining a constant V/Hz ratio keeps torque manufacturing secure. While it will be ideal to increase the voltage to the motor as it’s run above its rated pace, the voltage of the alternating present (AC) energy supply limits the maximum voltage that’s obtainable to the motor. Therefore, the voltage supplied to the motor can not continue to increase above the nameplate voltage as illustrated in Image 2. As proven in Image 3, the available torque decreases past 100% frequency as a result of the V/Hz ratio is not maintained. In หลักการทํางานของpressuregauge , the load torque (pump) should be under the available torque.
Before working any piece of kit outside of its rated speed range, it is essential to contact the producer of the gear to determine if this may be accomplished safely and efficiently. For extra information on variable pace pumping, discuss with HI’s “Application Guideline for Variable Speed Pumping” at

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