In some instances, working a motor past the base pole pace is feasible and presents system benefits if the design is rigorously examined. The pole speed 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 through 12-pole motors at 50 hertz (Hz [common in Europe]) and 60 Hz (common within the U.S.). As illustrated, extra poles reduce the bottom pole velocity. If the incoming line frequency does not change, the speed of the induction motor might be less than these values by a % to slip. So, to operate the motor above the bottom pole speed, the frequency must be elevated, which may be carried out with a variable frequency drive (VFD).
One reason for overspeeding a motor on a pump is to use a slower rated velocity motor with a decrease horsepower rating and function it above base frequency to get the required torque at a lower present. This allows the choice of a VFD with a decrease present score for use whereas nonetheless guaranteeing satisfactory management of the pump/motor over its desired working range. The decrease present requirement of the drive can scale back the capital value of the system, relying on total system necessities.
The purposes where the motor and the driven pump operate above their rated speeds can provide further circulate and stress to the managed system. This might lead to a extra compact system whereas growing its efficiency. While it could be possible to extend the motor’s velocity to twice its nameplate velocity, it is more frequent that the utmost velocity is more limited.
เกจวัดแรงลม to those applications is to overlay the pump pace torque curve and motor speed torque to make sure the motor starts and functions all through 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 solutions:
Noise will enhance with velocity.
Bearing life or greasing intervals may be reduced, or improved match bearings may be required.
The greater speed (and variable speed in general) will enhance the chance of resonant vibration due to a crucial velocity within the operating range.
The larger speed will end in further power consumption. It is essential to consider if the pump and drive practice is rated for the higher energy.
Since the torque required by a rotodynamic pump will increase in proportion to the sq. of velocity, the other main concern is to make sure that the motor can present enough torque to drive the load at the elevated velocity. When operated at a pace below the rated velocity of the motor, the volts per hertz (V/Hz) could be maintained as the frequency applied to the motor is elevated. Maintaining a constant V/Hz ratio keeps torque manufacturing secure. While it would be best to increase the voltage to the motor as it’s run above its rated pace, the voltage of the alternating current (AC) energy supply limits the utmost voltage that’s available to the motor. Therefore, the voltage equipped to the motor can’t continue to increase above the nameplate voltage as illustrated in Image 2. As shown in Image 3, the out there torque decreases past 100% frequency because the V/Hz ratio is not maintained. In an overspeed scenario, the load torque (pump) should be beneath the out there torque.
Before working any piece of apparatus outside of its rated speed vary, it’s important to contact the manufacturer of the gear to discover out if this can be carried out safely and effectively. For more info on variable speed pumping, check with HI’s “Application Guideline for Variable Speed Pumping” at pumps.org.
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