DC MACHINES AND COMPUTER AIDED DESIGN QUESTIONS FOR PRACTICES

1. Determine diameter and length for 100 Kw, 230V, 750 rpm, 6 pole dc machine. How the choice is made for selecting pole numbers in a dc machine.

2. Find the suitable number of poles and the dia. of the core of a 400Kw, 550 V, 180 rpm d.c. generator having 92% efficiency. Assume an average flux density in the air gap of about 0.6 wb/m² and ampere conductor per meter to be 35000.

3. Explain the use of a digital computer in designing of an electrical machine giving its advantages and limitations.

4. Give Computer Aided Design approaches  by the following methods:

(a)    Analysis

(b)   Synthesis

(c)    Hybrid

5. Give concept of optimization as applied to the design of electrical machines. Name some of the optimization techniques employed in design and briefly describe its general procedure.

6. Explain the design procedure for design of stator of a 3-phase turbo-alternator and write a flow chart to estimate the main dimensions. What statements will have to be changed to make the same program valid for a water wheel generator.

7. If the design data of a single phase transformer is known, write flow chart for determining % regulation and efficiency at different load currents and power factors.

8. Give design procedure for design of rotor of a wound rotor induction motor.

9. Explain, with flow chart, how the performance of a water wheel generator may be estimated from the design data and what steps can be taken to improve the performance.

10. Write a flow chart to design a d.c. machine and estimate its efficiency.

11. Write a procedure to obtain the leakage reactance of a 3-phase core-type transformer with concentric winding with its relevant computer flow chart and indicate how the value of leakage reactance be controlled by design parameters.