The speed of separately excited dc motor can be control by changing the armature voltage and changing field flux. Due to this the speed can be controlled for below rated speed and speed above the rated speed, respectively.
How can you control the speed of a separately excited DC motor?
2 Speed control techniques in separately excited dc motor: i) Varying the armature voltage in the constant torque region. ii) In the constant power region, field flux should be reduced to achieve speed above the rated speed.
In what application does speed control of DC separately excited motor becomes useful?
Separately excited DC motors are often used as actuators in trains and automotive traction applications. For their constant speed characteristics, shunt DC motors are used in fixed speed applications such as fans. square of armature current), they can be used in applications that require high starting torque.
How is the speed of a DC separately excited motor influenced by an increase in armature voltage?
In the fifth part of the exercise, you will demonstrate that when the armature voltage ܧ is set to a fixed value, the speed of the separately-excited dc motor decreases with increasing armature current or torque because of the increasing voltage drop across the armature resistor.
How do you control 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 three speed control methods for separately excited DC?
There are several techniques of speed control of DC drives – armature voltage control, armature resistance control and field flux control.
What is the advantage of separately excited DC motor?
Separately excited DC generators have many advantages over self-excited DC generators. It can operate in stable condition with any field excitation and gives wide range of output voltage. The main disadvantage of these kinds of generators is that it is very expensive of providing a separate excitation source.
What are the 4 types of DC motor?
There are 4 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 are the 3 types of DC motors?
Types of DC Motors. There are 3 main types of DC motor that are available:- Series, Shunt and Compound. These terms relate to the type of connection of the field windings with respect to the armature circuit.
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.
How does a separately excited DC motor is different from other motors?
Separately Excited DC Motor
The main distinguishing fact in these types of DC motor is that, the armature current does not flow through the field windings, as the field winding is energized from a separate external source of DC current as shown in the figure beside.
How do you reverse the direction of rotation of DC separately excited motor?
Hence the direction rotation of the motor can be reversed by reversing the current through either the armature winding or the field coils. If the current through both is reversed, the motor will continue to rotate in the same direction as it was rotating previously.
What is armature voltage in a DC motor?
Armature voltage is the voltage developed at the terminals of the armature winding of an AC or a DC machine during generation of power.
What is the speed of dc motor?
DC controls adjust speed by varying the voltage sent to the motor (this differs from AC motor controls which adjust the line frequency to the motor). Typical no load or synchronous speeds for an AC fractional horsepower motor are 1800 or 3600 rpm, and 1000-5000 rpm for DC fractional hp motors.
What is meant by speed control of dc motor?
Often we want to control the speed of a DC motor on demand. This intentional change of drive speed is known as speed control of a DC motor. Speed control of a DC motor is either done manually by the operator or by means of an automatic control device.