Why do we need to control the speed of motor?
In mechanical system, speed varies with number of task so speed control is necessary to do mechanical work in a proper way. It makes motor to operate easily. Shunt motor is a special type of DC motor which runs at a constant speed. But using field and armature rheostat control method we can make it more versatile.
What is the need of speed control of an induction motor?
Speed control of induction motor is done in this method by injecting a particular voltage in the rotor diagram. The injected voltage (emf) needs to have an equal frequency with the slip frequency. However, there is no limitation for the phase of that emf.
What is the rated speed of the motor?
Rated Speed is the speed of the motor (stated in R.P.M) at which it produces its rated (maximum) power, when the specified (rated) voltage is given at its rated Load. While, maximum speed is the maximum attainable speed in a motor without damaging the bearings and other components of the motor.
Why is it necessary to reduce the voltage to a motor when the frequency is reduced?
When motor operates at lower V/Hz than rated, the magnetic flux is reduced. Reduced flux reduces the torque capability and affects the motor ability to handle the load. Lower voltage while supply frequency is constant means lower V/Hz ratio and lower flux which affects the torque.
How does frequency affect motor speed?
Varying the voltage frequency affects both the motor speed and the strength of the magnetic field. When the frequency is increased (for higher motor speed), the magnetic field decreases, and lower torque is produced. In order to keep the magnetic flux constant, the V/Hz ratio must remain constant.
What is the relationship between generator load, speed?
On a generator, you have a prime mover (say, an engine) connected to the actual generator, which consists of either rotating coils of wire within a magnetic field, or rotating magnets surrounded by coils of wire. The number of poles (magnetic poles) and the rotational speed determine the output frequency: Freq = Engine_RPM * Number_Of_Poles / 120.
Which is a better measure of generator power?
RATED power is a more reliable measure of generator power. It is the power that a generator can produce for long periods of time. Typically the RATED power is 90% of the MAXIMUM power. The light bulb example is called a RESISTIVE type load and the POWER it requires is pretty easy to understand.
Why does a generator need a duty rating?
The generator power output and duty ratings must be properly selected to meet the demand of the connected loads. The relative size of the connected load compared to the generator capacity will impact the generator performance. Too much load on the generator may cause the generator to not start when needed.
What happens when a motor is started on genset power?
However, when a motor is started on genset power, the high inrush currents (measured in kilovolt-amperes or KVAs) can result in a large voltage dip that can inhibit the motor from reaching its operating speed. The challenge, then, is to size the genset to handle the motor-starting load, but also