Week-7 Challenge: DC Motor Control

EV LIVE BATCH 2021

1)

A)

The H-bridge consists of four BJT/Diode pairs (BJT simulated by IGBT models). Two transistors are switched simultaneously: Q1 and Q4 or 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

B)

In the above plots we can see the IGBT and diode current. From this we can see current shoots up. So we can see that armature current also shoots up

C)

four quadrant chopper can operates in all four modes, but H bridge can operate only in two modes

In four quadrant chopper regenerative braking is possible, but H bridge regenerative braking is not possible.

In four quadrant chopper two PI regulator is used to obtain electromagnetic torque needed to reach the desired speed and control the armature current adn stabilize the system, but in H bridge model PI regulator is not used

2)

Two quadrant chopper

In this type of chopper the average voltage will be always positive but the average load might be positive or negative. The two switches CH1 and CH2 should not be turned on simultaneously as the combined action may cause a short circuit supply lines. For regenerative braking and motoring these type of chopper configuration is used.

3)

Stator windings of a BLDC motor are connected to a control circuit. The control circuit energizes proper winding at proper time, in apattern which rotates around the stator

The rotor magnet tries to align with the energized electromagnet of the stator, and as soon as it aligns, the next electromagnet is energized.

Commutator and brush arrangement is eliminated in a brushless dc motor. And an integrated switching circuit is used to achieve unidirectional torque.