Power electronics

[DhineshAsimov]

*An electric resistance space heater rated at 1500W for a voltage source of v(t)=120√(2) sin(2pi60t)V has a thermostatically controlled switch. The
heater periodically switches on for 5 min and off for 7 min. Determine
(a) the maximum instantaneous power, (b) the average power over the
12-min cycle, and (c) the electric energy converted to heat in each 12-min
cycle.

[altenbach]

Are you looking for help with your homework?

[johnsold]

The problem as stated cannot be solved. It is missing key information.

Lynn

[DhineshAsimov]

Yes sir..Im taking Power Electronics subject and we are using Mc Graw Hill Book ( The international Edition) by Daniel W. Hart..
I have tried many question yet im not sure whether the asnwer is correct or not.. Where can i get the solution of the book..?

thank u in advance..

[johnsold]

People who participate on the Forums do not do your homework for you . We will try to help you, particularly with understanding how to use National Instruments products.

I do not have that book and I do not know if any answer key is available.

Please show us what you have tried and why you have doubts about the quality of the result.

My concern with the completeness of the statement of the problem is this:

- The statement specifies the rating of the heater but does not specify the actual applied voltage. Are you to assume that rated voltage is applied?

As for how to approach the problem, consider breaking it down into simpler parts. What information do you need for part (a) which is not given directly in the problem statement? That leads to other questions: What information do you need to calculate instantaneous power? What information do you need to calculate maximum power? How can you get the information from the given statement?

Lynn

[altenbach]

As Lynn pointed out, the question has not enough information to be answered in general. For example the maximum instantaneous power will depend on the termperatrure/resinstance relationships as well as the reactance of the heating element and the actually applied voltage (not the rated voltage).

In the trivial limiting case of a purely resistive heating element with no reactance and negligible temperature coefficient, and operating at the rated voltage, the problem can be easily solved. What is giving you problems?

Sometimes you can simply type the first few words of the problem into google and you'll find many links where this exact problem has been discussed. ( for example here, No guarantee that the solution is correct ;)).