Eng Proguide Exam questions discussions

[No message]

Question 5 solution is also wrong. 

Once you choose Generator voltage as a base then the base voltage for motors would be 120V because of 480/120 v transformer therefore the answer should be 0.6 PU and that choice is not available. 

On question 1 the answer should be 295.8 -j 183.4 ohms. So I think they just missed the minus sign. 

roy167 said:

Question 5 solution is also wrong. 

Once you choose Generator voltage as a base then the base voltage for motors would be 120V because of 480/120 v transformer therefore the answer should be 0.6 PU and that choice is not available. 

On question 1 the answer should be 295.8 -j 183.4 ohms. So I think they just missed the minus sign. 

Click to expand...

He does choose 120V as the base voltage for the motor.  "Vmotor=120V; Zmotor=0.6pu"  You then convert to the generator base to get to the solution. Am I missing something?

MEtoEE said:

He does choose 120V as the base voltage for the motor.  "Vmotor=120V; Zmotor=0.6pu"  You then convert to the generator base to get to the solution. Am I missing something?

Click to expand...

He may have changed it now. See Justin's comment above.  My point was, you choose base voltage in any one zone and then transformer will dictate the base voltages in other zones. If the transformers are involved that is. What I had seen was their question not following this rule. 

Sorry I didn't see Justin's comment.  Is it in another thread?  I'll look.  Thanks!

yes it is in graffeo thread. 


osted December 20 (edited)





  On 12/20/2018 at 6:29 PM, roy167 said:
Question 5 solution is also wrong. 

Once you choose Generator voltage as a base then the base voltage for motors would be 120V because of 480/120 v transformer therefore the answer should be 0.6 PU and that choice is not available. 


I do see what you are saying and I agree, thank you.  We tried to make the problem a little bit more tricky and to have the reader use the value of 480 V as the base voltage for the entire circuit and to override what is normally done.  Thank you for the input, I will revise the solution.