Week-7 Challenge: DC Motor Control
Question 1
This the image of the Model speed control of DC motor using BJT H-brige
This is called H bridge beacause the the aggrangment of the devices around the DC motor is alfabet H.
there 4 IGBT (Insulated gate biapolar transister) Q1,Q2,Q3,and Q4. and four diode D1,D2,D3 And D4. are used t control the speed .
battery of 240 volts is applied to the curuits.
when Q1 and Q4 are in on state positive voltage flow through DC motor and D1 and D4 are in free wheeling state.when there Q1 and Q4 are off to protect them from unwanted current.
when Q3 and Q2 are in on state a negative Voltage flows through the DC motor and diode D3 and D4 are in free wheeling state when Q3 and Q4 are off to protect them from unwanted current.
when we RUN the model for 1 sec following result are generated
Current of Diode and IGBT
we can see both the graph are in alternate ,this indiacte that either one of them is in active state.
following are the result of RPM,Armature current, and Torque.
input of the pusle modulation block of the is model is 75%, means its 75% 0f its total time .the switch will be on for 0.75 sec from total 1 sec .
image shows the input parameters of the pulse modulation block.(refer to the width of the pulse)
now we will change the input pulse width from 75% to 50% and observe the resuls of the aramture current.
scope result of the aramture current.
from the result we can see that the sudden shoot after the 0.5 sec in negative ,has degrease after changing the pule modulation width from 75% to 50% .
Queston 3
Working of BLDC motor
BLDC stand for Brush less DC motor.
the operation is similar to the Brused motor Dc
In brused motor there are brush for communication for supply but in BLDC their are no brush insteated of it their is a communication device present.
The Lorentz force law which states that whenever a current carrying conductor placed in a magnetic field it experiences a force. As a consequence of reaction force, the magnet will experience an equal and opposite force. In the BLDC motor, the current carrying conductor is stationary and the permanent magnet is moving.
When the stator coils get a supply from source, it becomes electromagnet and starts producing the uniform field in the air gap. Though the source of supply is DC, switching makes to generate an AC voltage waveform with trapezoidal shape. Due to the force of interaction between electromagnet stator and permanent magnet rotor, the rotor continues to rotate.
With the switching of windings as High and Low signals, corresponding winding energized as North and South poles. The permanent magnet rotor with North and South poles align with stator poles which causes the motor to rotate.
Advantage of BLDC motor
less maintenance due to absent of brush
high speed ,low eletric nosie genration
due to use of permenent magnet rotor high efficiency and high output power to size ratio.
long life of the motor.
Limitation the BLDC motor
the cost of motor is high
the electronic controller to control this motor is expensive
there is need od addtional sensors.
applications
in pumps compressor
in electronic decive like DVD
In electric vehicle,hybrid vehicle and electric bycycle
comparision between DC7 chopper and H bridge.
in this block od DC7 the current is controlled by the PI controller and in H bridge its controlled through pulse generator.
DC chopper are very costly as compare to H bridge.
Dc chopper are used in electric vehicle where H bridge are used in compressor and pumps.
Power level is high in Dc chopper but low in H bridge.
Sinmulink aggranement of 2 qudrant
