ELEC3565 Assignment (2024-2025)

Part 1 – DC Machines

1a) Based on the estimated gradients and y-intercepts, and the speed-current relationship from your lab on DC machines, explain and show how the machine constant and armature resistance are obtained through the lab work. At the end of the explanation, you should clearly state the values of the machine constant and armature resistance.

1b) Using the values for the parameters stated in 1a), present the speed-current characteristics for all the measured armature voltages obtained from the lab work. Ensure that your axes are labelled, and your plot/s have titles. These could either be drawn using MATLAB, MS Excel or another drawing software.

1c) Based on the speed-current characteristics you have presented in 1b), show and explain how you would estimate the values of no-load speed and starting torque for each armature voltage case.

End of Part 1

Limit your answers to a maximum of 5 pages for Part 1 – including all tables, figures and text (see assessment brief). Do not repeat question text in your submission.

Part 2 – Induction motor

2a) Clearly show your derivation of the parameters of R'2, X1, X2', RC and Xm. Consider the following:

· You should start your solution by stating the measurements of voltage, current and power taken during the locked-rotor and no-load tests.

· You are only expected to show major calculation or derivation steps.

· At the end, list out the numerical values of R'2, X1, X2', RC and Xm you have derived.

2b) Based on the rated power and speed of the motor (in rad/sec) given in the lab sheet and using the parameters you have derived in Section 2a), calculate the following:

· Rated slip speed

· Rated slip

· Rated motor torque

· Rated frequency of the rotor current in Hz (fr).

· Rated rotor phase current (I'2)

You must show all steps in your calculations.

Comment briefly on how the difference (if any) in stator resistance under warm DC resistance measurements would impact performance.

2c) Based on the equivalent circuit used for this lab, draw a phasor diagram to represent the relationships among the following quantities:

· I'2

· Im

· Ic

· I1

· E1

· Vph

where E1 is the voltage across Xm and Rc.

You must include any comments to justify your drawing. You are free to sketch this by hand or using suitable software, so as long it is neatly drawn, easy to follow and clearly labelled. The diagram does not need to be drawn to scale.

End of Part 2

Limit your answers to a maximum of 5 pages for Part 2 – including all tables, figures and text (see assessment brief). Do not repeat question text in your submission.