Question help (301)

[bob251]

Hi I have my 2330-301 coming up and its time I got these formulas I been stuck on out the way could you please help me by working it out and telling me how you done it, I will seriously appreciate it, thanks alot!

The air gap in a conductor is 25mm squared, the flux density is 1.5 T. calculate the total flux.

How many numbers of turns are needed on a transformer if the primary windings are 1000 and the primary and secondary current are 5A and 20A respectively.

A transformer has an output of 12 KVA and a power factor of 0.9. The total losses in the transformer are 600w. What is the effeciency of the transformer?

A transformer takes a load of 50 KVA with an input of 37 KW. What is the total power factor?

A transformer takes a load of 25 KVA at a power factor of 0.8. Calculate the input in KW.

A small heating circuit draws 1.5 KW of power and has an internal resistance of 0.5 ohms. What is the total current?

The resistance of a 230V 3 KW wall mounted heater will be?

If a current of 200 mA flows into a capaciator for 40mS, how much charge will develop in the capaciator?

A medium sized factory has a three phase load of 50 KVA and 30 KVAr, calculate the power factor.

 

[Phil]

Free Online Calculators for Engineers - Electrical, Mechanical, Electronics, Chemical,Construction, Optical, Medical, Physics, etc...

electrical calculator that may help you

 

[bob251]

Thanks for that but its quite useless to me as it doesn't tell me how to do it

 

[Guest123]

Hi I have my 2330-301 coming up and its time I got these formulas I been stuck on out the way could you please help me by working it out and telling me how you done it, I will seriously appreciate it, thanks alot!

The air gap in a conductor is 25mm squared, the flux density is 1.5 T. calculate the total flux.
W = BxA = 1.5 x 25 x 25 x 0.0010 = 0.93Wb.

How many numbers of turns are needed on a transformer if the primary windings are 1000 and the primary and secondary current are 5A and 20A respectively.

A transformer has an output of 12 KVA and a power factor of 0.9. The total losses in the transformer are 600w. What is the effeciency of the transformer?

A transformer takes a load of 50 KVA with an input of 37 KW. What is the total power factor?
PF = True power / Apparent power = 37000 / 50000 = 0.74

A transformer takes a load of 25 KVA at a power factor of 0.8. Calculate the input in KW.
KW = KVA x PF = 25 x 0.8 = 20KW.

A small heating circuit draws 1.5 KW of power and has an internal resistance of 0.5 ohms. What is the total current?
I = Sqrt of W/R = 1500sqrt / 0.5 = 54.77A.

The resistance of a 230V 3 KW wall mounted heater will be?
R = Vsquared/W = 230squared / 3000 = 17.6ohms.

If a current of 200 mA flows into a capaciator for 40mS, how much charge will develop in the capaciator?

A medium sized factory has a three phase load of 50 KVA and 30 KVAr, calculate the power factor.

Theres a few I managed to remember, and now my swede is hurtin.....

 

[Phil]

just been looking through some of the handouts we got when i was on the course, there is boat loads of them will take me hours to pick some out if i find anything thats any good i will send it to you, pm me your email address and i will send them over

 

[bob251]

Thanks alot lenny and phil I just been working through some and I think I cracked the second 1

How many numbers of turns are needed on a transformer if the primary windings are 1000 and the primary and secondary current are 5A and 20A respectively

20/5=4 1000/4= 250 turns (this was a multiple choice question and 250 is one of the awnsers)

 

[Phil]

sent email for you will send some more bits when i find them

 

[bob251]

What is the symbol on the calculator for squared I think it is the tick3 or 1.732 but it does not work on these questions?

A small heating circuit draws 1.5 KW of power and has an internal resistance of 0.5 ohms. What is the total current?
I = Sqrt of W/R = 1500sqrt / 0.5 = 54.77A.

The resistance of a 230V 3 KW wall mounted heater will be?
R = Vsquared/W = 230squared / 3000 = 17.6ohms.

 

[Guest123]

Square Root.....





Squared.....x2

 

[bob251]

Thanks I got it now

 

[bob251]

I need help again please with this one ( I have been searching the net and my notes im quite stumped)

A 30KW 3 phase delta connected motor has a power factor of 0.86 lagging. Calculate the line current.

A)53.05A
B)62.35A
C)50.35A
D)5.35A

 

[Guest123]

C)50.35a

 

[bob251]

Nice one how did you work that out lenny?

 

[Guest123]

For 3phase design current (Ib).....

KW / (V x Root3 x PF) = 30,000 / (400 x 1.732 x 0.86) = 50.35A.

 

[bob251]

Ah I wasn't putting in the 400v because it wasn't in the question dam stupid mistakes