VFDs can be used not only to slow down a motor, but also to drive it beyond its rated speed (overspeed) by increasing the VFD output frequency above 60 Hz. Some HVAC equipment manufacturers overspeed a motor to allow for fan and motor combinations that really shouldn’t have been allowed in the first place.
What happens when you overspeed a motor?
In cases where motors are operating at an overspeed condition, this change in mode of operation could result in serious consequences, such as airflow reversals and impact to room air change rates. The motor-driven machinery must also be carefully evaluated for operation.
Can an electric motor overspeed?
Average 2 pole industrial motors can safely exceed its base speed by 25%. Many manufacturers balance their 2 pole and 4 pole rotors to the same speed – 25% over the 2 pole base speed. A 2 pole motor may therefore operate up to 125% over base speed before reaching its balance limit.
How can I speed up my motor?
Increasing the speed can be achieved by increasing the supply frequency as the speed and frequency are directly proportional; however, there are two constraints. The first is the saturation of the magnetic circuit, but this issue can be significantly avoided by keeping the V/f ratio constant.
Can you change the speed of a motor?
AC motors are constant speed devices but their speed can vary if you change the input voltage or frequency or the windings that make the motor rotate. The most common and efficient way of changing the speed is to vary the frequency by using an inverter as the power supply.
What is overspeed protection?
Unlike the Core 2 or Pentium D processors, the Core i7 CPU can monitor the current it draws as well as its power consumption—if it exceeds a certain level, the processor automatically reduces its clock speed. Intel calls this feature “Overspeed Protection.” The limits hard-wired into the core are 100 A and 130 watts.
What is the cause of overload of the engine?
Motor overload occurs when a motor is under excessive load. The primary symptoms that accompany a motor overload are excessive current draw, insufficient torque and overheating. Excessive motor heat is a major cause of motor failure.
What determines the RPM of an electric motor?
The rotating speed of an electric motor depends on two factors: its physical construction, and the frequency (Hz) of the voltage supply. Electrical engineers select the speed of a motor based on the needs of each application, similar to how the mechanical load determines the horsepower required.
What is the maximum rpm of an electric motor?
In this case, unless external limitations are applied, the maximum torque is achieved at low RPM. For example, the AC motor found in the Tesla Roadster (2008) produces near constant maximum torque from 0 to about 6000 RPM, while maximum power occurs at about 10000 RPM, long after torque begins to drop off.
Why will a motor not work without a commutator?
No, a direct current motor cannot run without a commutator because there is no induced electromotive force inside the armature. The commutator plays the function of supplying current to the armature from the brush. That is why the armature removed will not supply the motor. Further, it will stop the running.
What makes an electric motor slow?
The most common cause of motor failure, and arguably the most difficult to overcome, is low resistance. Low resistance is caused by the degradation of the insulation of the windings due to conditions such as overheating, corrosion, or physical damage.