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

In ตัววัดแรงดันน้ำ , operating a motor beyond the base pole speed is feasible and offers system advantages if the design is carefully examined. The pole speed of a motor is a operate of the quantity poles and the incoming line frequency. Image 1 presents the synchronous pole pace for 2-pole by way of 12-pole motors at 50 hertz (Hz [common in Europe]) and 60 Hz (common in the U.S.). As illustrated, extra poles cut back the base pole pace. If the incoming line frequency doesn’t change, the speed of the induction motor might be lower than these values by a % to slip. So, to function the motor above the base pole velocity, the frequency needs to be increased, which could be done with a variable frequency drive (VFD).
One cause for overspeeding a motor on a pump is to make use of a slower rated velocity motor with a lower horsepower rating and operate it above base frequency to get the required torque at a decrease current. This enables the selection of a VFD with a lower present ranking for use whereas still making certain satisfactory management of the pump/motor over its desired operating range. The decrease present requirement of the drive can cut back the capital value of the system, depending on overall system necessities.
The functions the place the motor and the pushed pump function above their rated speeds can provide further move and strain to the controlled system. This might end in a extra compact system while rising its efficiency. While it could be attainable to increase the motor’s velocity to twice its nameplate speed, it is more widespread that the utmost velocity is more restricted.
The key to those functions is to overlay the pump velocity torque curve and motor pace torque to ensure the motor begins and capabilities all through the whole operational speed range with out overheating, stalling or creating any vital stresses on the pumping system.
Several factors additionally have to be taken into consideration when considering such solutions:
Noise will enhance with velocity.
Bearing life or greasing intervals could also be lowered, or improved fit bearings may be required.
The greater speed (and variable velocity in general) will improve the danger of resonant vibration because of a crucial speed throughout the operating range.
The greater speed will result in extra power consumption. It is important to suppose about if the pump and drive practice is rated for the upper energy.
Since the torque required by a rotodynamic pump will increase in proportion to the sq. of pace, the other major concern is to guarantee that the motor can provide enough torque to drive the load at the increased speed. When operated at a speed below the rated pace of the motor, the volts per hertz (V/Hz) can be maintained as the frequency applied to the motor is increased. Maintaining a constant V/Hz ratio keeps torque manufacturing stable. While it would be perfect to extend the voltage to the motor as it’s run above its rated speed, the voltage of the alternating present (AC) power source limits the maximum voltage that is out there to the motor. Therefore, the voltage equipped to the motor cannot continue to extend above the nameplate voltage as illustrated in Image 2. As shown in Image 3, the out there torque decreases past 100 percent frequency as a outcome of the V/Hz ratio is not maintained. In an overspeed situation, the load torque (pump) should be beneath the out there torque.
Before working any piece of kit outdoors of its rated velocity vary, it’s important to contact the manufacturer of the equipment to discover out if this can be accomplished safely and efficiently. For more data on variable pace pumping, discuss with HI’s “Application Guideline for Variable Speed Pumping” at pumps.org.
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