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.
How does a separately excited DC motor work?
A separately excited dc motor is a motor whose field circuit is supplied from a separate constant-voltage power supply, while a shunt dc motor is a motor whose field circuit gets its power directly across the armature terminals of the motor. … Hence, the motor speed will slow down.
How do you start a separately excited DC motor?
When the separately excited DC motor starts rotating back emf produce which take care of the armature current by reducing the net voltage in armature winding. Hence the starter is no more required.
How can the direction of rotation of a separately excited DC motor be reversed?
Hence the direction rotation of the motor can be reversed by reversing the current through either the armature winding or the field coils. … Now in the case of separately excited motor, the direction of the motor can be reversed by reversing the supply terminals of either field circuit or armature circuit.
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.
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.
Why do DC motors need starters?
Starters are used to protect DC motors from damage that can be caused by very high current and torque during startup. They do this by providing external resistance to the motor, which is connected in series to the motor’s armature winding and restricts the current to an acceptable level.
Why DC motor starter resistance is connected?
DC series motor starter
Construction of DC series motor starters is very basic as shown in the figure. The start arm is simply moved towards right to start the motor. Thus, maximum resistance is connected in series with the armature during starting and then gradually decreased as the start arm moves towards right.
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 can you change the direction of rotation of a DC motor?
We can change the direction of DC motor 1) by changing the polarity of applied field voltage. 2) by changing the polarity of the applied voltage to the armature winding. 3) if we change both of the polarity of field and armature then the motor will rotate with previous direction…
How do you change the rotation of a DC motor?
The direction of rotation of the DC series motor can be changed only if the direction of either field current or armature current is changed. The direction of rotation of DC series motor may be reversed by changing; The polarity of the either field.