Contents
What is field flux in DC motor?
D.C. motors The series connection of armature and field windings (Fig. 3.15A) means that the field flux is directly proportional to the armature current, and the torque is therefore proportional to the square of the current.
How will you control the speed of DC motor using flux control method explain?
Flux control method It is already explained above that the speed of a dc motor is inversely proportional to the flux per pole. Thus by decreasing the flux, speed can be increased and vice versa. To control the flux, a rheostat is added in series with the field winding, as shown in the circuit diagram.
What are the drawbacks of field flux control of speed of DC motor?
Disadvantages of flux control method: (i) Only speeds higher than the normal speed can be obtained since the total field circuit resistance cannot be reduced below Rsh—the shunt field winding resistance. (ii) There is a limit to the maximum speed obtainable by this method.
How does dc motor increase RPM?
How to improve torque and RPM of a DC motor?
- Case 1: Increase/Decrease strength of permanent magnets. What would happen to torque and RPM?
- Case 2: Increase/Decrease size of magnet wires.
- Case 3: Increase/Decrease the size of armature.
- Case 4: Increase/Decrease the number of turns (coil).
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.
How is speed control of DC motor by varying field flux?
As shown in figure, a variable resistance called diverter is connected in parallel to the field winding of DC Series Motor. As the resistance of Diverter is changed, the field flux is changes which in turn cause the speed of DC Motor to change. The connection diagram of tapped filed control is shown in figure below.
What are the methods for controlling the speed of a DC shunt motor?
There are three general methods of speed control of a DC Motor. They are as follows. Variation of resistance in the armature circuit. This method is called Armature Resistance or Rheostatic control. This method is known as Field Flux Control. This method is also known as Armature Voltage Control.
How does the variable resistance affect the flux?
The variation in the variable resistance does not affect the flux as the field is directly connected to the supply mains. The speed current characteristic of the shunt motor is shown below. Now, let us consider a connection diagram of speed control of the DC Series motor by the armature resistance control method.
Which is better flux or armature speed control?
Both the above-mentioned methods cannot provide speed control in the desirable range. Moreover, the flux control method can affect commutation, whereas the armature control method involves huge power loss due to its usage of a resistor in series with the armature.