In some situations, working a motor past the base pole speed is feasible and offers system advantages if the design is fastidiously examined. The pole velocity of a motor is a function 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, additional poles scale back the base pole velocity. If the incoming line frequency does not change, the pace of the induction motor might be less than these values by a % to slip. So, to function the motor above the base pole velocity, the frequency must be increased, which could be carried out 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 permits the number of a VFD with a lower current score to be used whereas still guaranteeing satisfactory management of the pump/motor over its desired working vary. pressure gauge น้ำ of the drive can cut back the capital price of the system, depending on overall system necessities.
The functions the place the motor and the driven pump operate above their rated speeds can present extra circulate and stress to the managed system. This may lead to a more compact system while increasing its effectivity. While it could be attainable to increase the motor’s speed to twice its nameplate pace, it is more widespread that the utmost pace is extra restricted.
The key to those functions is to overlay the pump pace torque curve and motor speed torque to make sure the motor begins and functions throughout the entire operational pace range without overheating, stalling or creating any vital stresses on the pumping system.
Several factors also have to be taken into consideration when considering such solutions:
Noise will improve with pace.
Bearing life or greasing intervals could additionally be lowered, or improved match bearings may be required.
The greater speed (and variable pace in general) will increase the chance of resonant vibration as a result of a important speed throughout the operating vary.
The greater speed will lead to further power consumption. It is important to consider if the pump and drive practice is rated for the upper power.
Since the torque required by a rotodynamic pump increases in proportion to the square of velocity, the opposite main concern is to make sure that the motor can provide enough torque to drive the load on the increased speed. When operated at a speed below the rated velocity of the motor, the volts per hertz (V/Hz) may be maintained because the frequency utilized to the motor is increased. Maintaining a continuing V/Hz ratio keeps torque manufacturing steady. While ตัววัดแรงดันน้ำ would be ideal to increase the voltage to the motor as it is run above its rated pace, the voltage of the alternating current (AC) power supply limits the utmost voltage that’s obtainable to the motor. Therefore, the voltage supplied to the motor can not proceed to increase above the nameplate voltage as illustrated in Image 2. As proven in Image three, the obtainable torque decreases past 100 percent frequency because the V/Hz ratio is not maintained. In an overspeed situation, the load torque (pump) have to be beneath the out there torque.
Before working any piece of apparatus outside of its rated speed range, it’s essential to contact the producer of the gear to discover out if this can be accomplished safely and efficiently. For extra data on variable speed pumping, check with HI’s “Application Guideline for Variable Speed Pumping” at pumps.org.
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