Week-7 Challenge: DC Motor Control

Q 1. A

Here we are going to control the speed of the DC MOTOR by uding the BJT H BRIDGE were importantly at first we need kown about the working of the H bridge BJT .

The H-bridge consists of four BJT/Diode pairs . Two transistors are switched simultaneously at a time Q1 and Q4 or elae Q2 and Q3. When Q1 and Q4 are fired, a positive voltage is applied to the motor and diodes D2-D3 operate as free-wheeling diodes when Q1 and Q4 are switched off. When Q2 and Q3 are fired, a negative voltage is applied to the motor and diodes D1-D4 operate as free-wheeling diodes when Q2 and Q3 are switched off.The motor starts in the positive direction with a duty cycle of 75% which mean DC voltage of 180V. At t= 0.5 sec., the armature voltage is suddenly reversed and the motor runs in the negative direction.

MODES

Q1 and Q4 are forward motoring modes

Q 2 and Q3 are reverse motoring modes

finally after the simulation it shows the simulation of the H BRIDGE which is used to generate the chopped voltage which is used to control the speed of the DC motor where the DC MOTOR is connected to the battery and the dc motor mechanical input is initialised as the TORQUE and the ouitput of the dc motor is connected with a bus sector and the speed is plotted in the scope

q1B

The modal which we seen is with a PULSE WIDTH of 75% hence at first there will an sudden rise in the ARMATURE CURRENT and hence speed is increased and also the torque of the motor is increased hence the motor motor moved forward after 0.5 sec there is sudden down in the armature current which is followed by sudden decrease in the speed and torque

And now we have to run the simukation with pilse width is 50% noe there is no sudden rise in the armature current hence speed and torque are in stable

Q1C FOUR QUADRANT OPERATION OF CHOPPER DC DRIVE(DC7)

Here therte are 4 modes are involving in the operations they are

1.FORWARD MOTORING : this mode is presented in the 1st QUADRANT where the power developed wil be in positive and the machine is going to work as an MOTOR with the nspeed torque and power all in the positive direction

2.FORWARD BREAKING MODE: This mode ilied in an 2nd QUADRANT where regenerative braking is applied to the motor.here the speed is positive but the torque and power is in neagative range

3.REVERSE MOTORING MODE: This mode ilied in an 3RD QUADRANT if the voltage polarity and the load current is reversed then the motor runs in the opposite direction but the power will be consumed by the load and the speed and torque will be in NEGATIVE but the power is positive

4.REVERSE BREAKING MODE : THIS MODE IS 4th QUADRANT .where we operate the motor by the reversing the voltage polarity then the motor is said to be reverse regenerative operation.this is know as reverse regeneration ,mode.

Q2 BASIC TWO QUADRANT CHOPPER

In the two quadrant chopper the voltage will always be in positive and their load current will may be positive or negastive.also both the two switches CH1 and CH2 will not ON at same time for regeneraive braking and motoring this type of configuration is used .we will always get an positive oyput V0 with the freewheeling diode FD acros the load When the chopper CH1 is on the current flows from source to load. The inductor stores energy. When Ch1 turn OFF the freewheeling diode starts conducting and the output voltage v₀ will be equal to now the direction of the load current is reversed and the current i0 will flow towards the source the source And it will be posive regardless thr chopper is ON or the FD conducts.the load curent will be neagtive if the chopper is on or the diode D2 conducts we can say the chopper and FD operate together as A type chopper the average voltage applied will be positive but the avarage load current will be positive or negative the power flow may be lie in the first quadrant operation that is from source to load or from load to source in second quadrant

A simulink modal is cuild with the simulation time of 1sec and the pule width generator is used as input voltage(with duty cycle) the MOSFET has high switching frequency and its design operation is very simple and it can operate in the 2quadrant .

SIMULINK MODAL IS GIVEN BELOW

Q3.BLDC MOTOR

BLDC is stands for brushless dc motor

this brushless dc motor is desighned to get a hig speed and high torque

BLDC motors are superior to brushed DC motors in many ways, such as ability to operate at high speeds, high efficiency, and better heat dissipation.

BLDC motors are also referred as trapezoidal permanent magnet motors.

TYPES

1.Inner rotor type BLDC motor (rotating part is at middle)

2.outer rotor type BLDC motor(outer part is rotating)

CONSTRUCTION

This is inner rotor type DBLDC stator is stationary and copper winding is placed in BLDC

Three phase connection is given to the motor herev we taken as A B C

Rotor is made up of an PERMANENT MAGNET here we doesnt use any kind of brushes commutators instead of that on;y we are using permanent motors for the magnetic fields

WORKING AND OPERATIONS

Here we are going to give the phases to nthe windings in a one by one manner inorder to energise and for the continous rotation

Now we are going to energise the PHASE A and energise the coil which develpos an north pole where we have qan permanent magnet rotor which has rhe south pole end attracts by ther magnetic field north pole to create an rotation

Then PHASE A will be DEENERGISED and PHASE B will be ENERGISED noe this winding will gwt energised and produce an another pole which will be again attracts by the rotor creates an another movement

Then PHASE B will be DEENEGISED and PHASE C will be ENERGISED therefore there will be an continous production of the magnetic field which causes the permanent magnet rotor to rotatae continously

But itbis not possible to change the polarity manually and we dont know which phase is energised currently and what to be next inorder to ocvercome thios we have to use HALL SENSOR which is use to sense the position of the rotor continously and energise the ststor accordingly to that

DIAGRAM FOR THE BLDC IS GIVEN BELOW