Most of the factories, the choice of the dc machine as a driver or control element. Among the privileges from the ac machine has a high starting torque and has a range of velocity range that can be operated in both directions of rotation.
When the machine works as a motor, DGE generated (Eb) is less than the voltage applied at terminal voltage (V).
When the machine works as a generator, DGE generated (Eg) is greater than the voltage applied to the terminal voltage (V).
Two special use direct current motor, namely:
i. Have a high starting torque
ii. Has a different velocity range
i. Have a high starting torque
ii. Has a different velocity range
3 types of dc motor control :
a) Field Controlb) Armature Control
c) Voltage Control
Field Control
The purpose of this control is to reduce the flux by increasing the resistance of the field. When the flux reduced the speed of N can be increased (may reach 3 / 4 times the normal speed).
Advantage
- Slight loss of power at the circuit due to lack of control resulting flux.
Weakness
- The limited speed range.
- Slight loss of power at the circuit due to lack of control resulting flux.
Weakness
- The limited speed range.
Armature Control
In both motors, the resistance R connected in series with the armature. Thus the value of armature voltage Va can be reduced by making changes in the value of R. If the voltage drops at high R, the voltage Va is reduced. Indirectly, speed, N is also reduced.
advantages:
- Large range of speed control.
weakness
- Since the current is the resistance (R) then there is loss of power in the resistance.
In both motors, the resistance R connected in series with the armature. Thus the value of armature voltage Va can be reduced by making changes in the value of R. If the voltage drops at high R, the voltage Va is reduced. Indirectly, speed, N is also reduced.
advantages:
- Large range of speed control.
weakness
- Since the current is the resistance (R) then there is loss of power in the resistance.
Ward-Leonard System
Ward-Leonard system is a system typical configuration consists of the generator (angkir Control) which is coupled with a DC motor as a driver.
In this system, the motor field current loop (M) will be supplied by a separate dc supply. Electronic amplifier will control the strength of the If current, the coil field generator. Generated voltage will be the input voltage (V) angkir of the motor (m) where the speed is proportional to the voltage generated. In conclusion the motor speed can be varied by changing the control signal in electronic amplifiers.
advantages:
i. Requires low power control circuits.
ii. Rapid speed changes and changes of direction of rotation can be done.
iii. Be adjusted in automation control systems.
iv. Provides great range and precise control.
Weaknesses: Cost is high because of using two motors and an electronic amplifier.
Uses: Control of motor speed milling machines running, the rotor and the coal mine.
In this system, the motor field current loop (M) will be supplied by a separate dc supply. Electronic amplifier will control the strength of the If current, the coil field generator. Generated voltage will be the input voltage (V) angkir of the motor (m) where the speed is proportional to the voltage generated. In conclusion the motor speed can be varied by changing the control signal in electronic amplifiers.
advantages:
i. Requires low power control circuits.
ii. Rapid speed changes and changes of direction of rotation can be done.
iii. Be adjusted in automation control systems.
iv. Provides great range and precise control.
Weaknesses: Cost is high because of using two motors and an electronic amplifier.
Uses: Control of motor speed milling machines running, the rotor and the coal mine.
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