Week-7 Challenge: DC Motor Control

Question - 1

This given Circuit below is the "Speed Control of a DC Motor using BJT H-Bridge"
In this circuit we can find all major components added such as,

• DC Motor (5 HP 240V 1750 RPM Field:300V) as preset
• Pulse Generator
• Duty Cycle
• Diode
• Battery
• Transistor
• BJT H-Bridge and others.

The Duty Cycle is preset at 75% = 180V

(i) Circuit Representation

(ii) Simulation of the Circuit

Speed, Armatur Current, Load Torque

IGBT Current and the Diode Current

As per the given Simulated Scope values it is represented that the motor is running in the clockwise direction for a certain duration and then running at anti-clockwise direction, as the motor specification and the duty cycle are referred the Current Plummet at a negative stage of -65 Amp. The Load torque also reduces with the opposite directional rotation of the Motor.

Making Modifications in the given model so that the armature current does not shoot up while the motor changes its direction from forward to reverse.

1. It is only possible by either selecting a higher grade motor which delivers higher voltage and has the capacity to handle the change in the motor operational direction.
   
   
2. Changing the Duty Cycle from 75% to a lower range.

Let me perform both these actions for you and denote the change in the Armature Current

Activity - 1 (Changing the Motor from 5 HP 240V 1750 RPM to 5 HP 500V 1750 RPM)

(iii) The given representation and the change in Armature current is as below,

Now the Armature Current goes to the minimum range of -15 Amp. It is changed from -65 Amp to -15 Amp which could be considered as the positive aspect and fulfilling our need. But the work output (Speed) in rpm is reduced by nearly 40%.

Activity - 2 (Changing the Duty Cycle from 75% to 65% with the same Motor as preset)

Considering the First Simulated range of shoot up of Armature Current here it is -45 Amp and in the initial stage with 75% of Duty Cycle the same was at -65 Amp.

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Question - 2

The DC7 Four Quadrant Chopper DC Drive model is as indicated below,

It has Four Quadrants for operations and also has two Pi IGBT controller for varying the signals. The regulators are Speed, Motor Torque, Voltage Chopper, Ground. Base sample is considered to be 10-e2

It has a 3 Phase Power source with 380 V 50Hz, the converter is fed by 515 V DC and then the AC to DC Converter that transfers the energu to the Chopper Drive which transmits the power to IGBT 1&4 and IGBT 2&3 which then follows the Duty cycle and following them are the Armature Voltage, Armature Current respectively.

The overall difference and comparison of the The Four-Quadrant Chopper DC Drive (DC7) are H-bridge model are as below,

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Question - 3

This is a DC7 Block with a EV Model

Few Blocks are added to comply and prepare a EV Model such as,

1. Drive Cycle - FTP75
2. Scope
3. Battery
4. Current Measurement
5. Torque Equation (Math Function w^2, Gain 0.0051, Constant 24.7, Sum Block)

The Drive Cycle inherits the feedback of the signals of time vs speed and the same is been input in the Speed Port, the Motor Torque Port is equivalent to the Speed of the motor, the Voltage of Chopper Circuit is conneced with the positive battery terminal and the ground is connected to the Negative/Earthing battery terminal. The same is then transferred to the Motor, Converter, Controller and the Speed of Motor.

The IGBT Converter assists in engaging the duty cycle which in combination assists for the forward, reverse rotation with the Current and voltage direction. The same is evaluated and simulated in the form of scope report as mentioned below,