Explanation: Speeds greater than rated speeds can be obtained by lowering the flux of shunt field motor. Field cannot be made any stronger, it can only be weakened by this method. Thus, speed lower than the rated speed can’t be obtained.
How can we control the speed of a DC shunt motor?
Thus, there are three general methods of speed control of D.C. Motors.
- Resistance variation in the armature circuit: This method is called armature resistance control or Rheostat control.
- Variation of field flux Ф This method is called field flux control.
- Variation of the applied voltage.
How may the speed of a DC shunt motor be increased above base speed?
The speed and torque of the system shown in ill. 2 can be controlled by adjusting the voltage to the field or to the armature, or both. Speeds above the motor base (nameplate) speed are obtained by weakening the motor shunt field with a rheostat or electronically.
Which method of speed control is used for DC shunt motor to obtain speed below rated speed?
Field Rheostat Controlled DC Shunt Motor
An increase in controlling resistances reduces the field current with a reduction in flux and an increase in speed. This method of speed control is independent of load on the motor. Power wasted in controlling resistance is very less as field current is a small value.
Which is the most effective way of controlling a DC shunt motor above rated speed?
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. Field rheostat provides above normal speed and armature rheostat provides wide range of below normal speed.
Why DC shunt motor is constant speed?
If the load on the motor increases armature speed reduces and thereby cause a reduction in the back emf. … Hence, a DC shunt motor always maintains a constant speed. Under no load condition, the back emf becomes nearly equal to the applied voltage.
How do you increase the speed of a DC motor?
Thus, the speed of a DC motor can be controlled in three ways:
- By varying the supply voltage.
- By varying the flux, and by varying the current through the field winding.
- By varying the armature voltage, and by varying the armature resistance.
What are the 3 types of DC motors?
Main Types of DC Motors
- Permanent Magnet DC Motors. The permanent magnet motor uses a permanent magnet to create field flux. …
- Series DC Motors. In a series DC motor, the field is wound with a few turns of a large wire carrying the full armature current. …
- Shunt DC Motors. …
- Compound DC Motors.
What is the principle of DC shunt motor?
Construction and Working Principle
The working principle of a DC Shunt Motor is, whenever a DC motor is turned ON, then DC flows throughout stator as well as the rotor. This current flow will generate two fields namely pole as well as the armature.
What is base speed of DC shunt motor?
Base speed is Hz multiplied by 60 then divides the result by half the number of poles. Rated speed is the base speed minus the slip at full rated load. An induction motor slows as it is loaded. 60 x 60 x 2 = 7,200 no-load rpm Ã· number of poles.
What are the factors affecting the speed of a DC shunt motor?
Factors Affecting The Speed Of Dc Motor
- The applied voltage.
- The flux.
- The voltage across an armature.
What will happen if excitation of DC shunt motor is changed?
2. What will happen if excitation of DC shunt motor is changed? … Explanation: Speed of the DC motor obtained from speed equation is inversely proportional to flux produced by the field. So, reducing the field current flux produced by armature will decrease, and speed will increase.
Which starter is used for DC shunt motor?
Three-point starter is used to start dc shunt motor | Electrical Machines.
How do you increase motor speed?
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.
Which DC motor is preferred for constant speed?
Explanation: Rotary compressor generally demand constant speed operation throughout the load. Sometimes, DC machines are not able to produce constant speed throughout the process hence, synchronous machine is used. 4.