HNC exam help im a bit lost on this.

[renevatio]

A 415V (line voltage), 50Hz, six-pole, star connected induction motor is rotating with a slip of 4.2%. The equivalent circuit components are

R[SUB]1[/SUB]= 0.18Ω R[SUB]2[/SUB]= 0.11Ω X[SUB]m[/SUB]= 13.2Ω
X[SUB]1[/SUB]= 0.39Ω X[SUB]2[/SUB]= 0.39Ω


from what i have gathered the speed is as below correct me if i am wrong.
Speed of shaft is 958rpm.

Line supply current?
Real input power?

please could you assist?

 

[Simonslimline]

Ns = f x 60 / P

50Hz x 60 / 3 Pairs of poles = 1000.

1000 x 4.2 /100 = 42.

I reckon 958RPM is correct. Not sure with the rest to be honest.

Looks more advanced than any questions we had at college. How are you finding the course anyway? I would like to do a HNC or HND one day myself, need to read lots of books and practise the theory more in depth first though.

 

[renevatio]

well its very heavy maths and i got A at a level its crazy understanding whats called J notation which is used in the next part to work out line current. would reccomend reading up on it. i am currently revising over for a retake of a failed exam.

 

[Simonslimline]

Yeah we never touched on j notation at college. Definitely something i will read up on. I am sure you will get some useful pointers from the more experienced people on here.

Best of luck with it mate

 

[Silly Sausage]

Haha...good question!
You're going to have to get your books & notes out for that one.
j-notation, or, complex (rectangular variety) numbers are really quite simple, honest!!!
They are used, along with the Equivalent circuit, because it makes the Maths a lot easier to get to the solutions.

It's a LONG time since I did this stuff, but I'll keep an eye on this one.