In some situations, working a motor beyond the base pole velocity is possible and provides system benefits if the design is carefully 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 speed 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 reduce the base pole velocity. If the incoming line frequency doesn’t change, the velocity of the induction motor will be less than these values by a percent to slip. So, to operate the motor above the bottom pole velocity, the frequency must be increased, which may be done with a variable frequency drive (VFD).
One purpose for overspeeding a motor on a pump is to make use of a slower rated velocity motor with a lower horsepower ranking and function it above base frequency to get the required torque at a decrease present. This enables the number of a VFD with a decrease present ranking to be used while nonetheless guaranteeing passable control of the pump/motor over its desired working vary. The decrease current requirement of the drive can reduce the capital value of the system, relying on general system requirements.
The applications where the motor and the driven pump function above their rated speeds can present extra flow and strain to the managed system. เกจวัดความดันน้ำ may result in a more compact system while rising its effectivity. While it might be attainable to increase the motor’s pace to twice its nameplate velocity, it’s more widespread that the maximum velocity is more limited.
The key to those applications is to overlay the pump speed torque curve and motor pace torque to make sure the motor begins and capabilities throughout the whole operational velocity range with out overheating, stalling or creating any vital stresses on the pumping system.
Several points also have to be taken into account when contemplating such solutions:
Noise will improve with speed.
Bearing life or greasing intervals may be reduced, or improved match bearings may be required.
The greater velocity (and variable velocity in general) will improve the chance of resonant vibration as a outcome of a crucial speed within the working range.
The greater velocity will end in extra energy consumption. It is necessary to contemplate if the pump and drive train is rated for the upper power.
Since the torque required by a rotodynamic pump increases in proportion to the sq. of speed, the other main concern is to make sure that the motor can provide enough torque to drive the load on the increased velocity. When operated at a speed beneath the rated speed of the motor, the volts per hertz (V/Hz) may be maintained because the frequency applied to the motor is elevated. Maintaining a continuing V/Hz ratio keeps torque manufacturing stable. While it will 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 source limits the maximum voltage that is 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 shown in Image three, the obtainable torque decreases past one hundred pc frequency because the V/Hz ratio just isn’t maintained. In an overspeed state of affairs, the load torque (pump) should be below the available torque.
Before operating any piece of apparatus outside of its rated velocity range, it’s essential to contact the manufacturer of the tools to determine if this can be done safely and efficiently. For more data on variable velocity pumping, check with HI’s “Application Guideline for Variable Speed Pumping” at pumps.org.
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