Electrical Engineering - Three-Phase Systems in Power Applications - Discussion

Correct answer is D:

as Va and Vb are 90 degree apart so;

Va=120<0; ---> polar form
Vb=120<90 ---> polar form.

Lets convert it into rectangular form
Va=120*(cos(0)+jsin(0)).
Va=120;
Vb=120*(cos(90)+jsin(90)).
Vb=j120;.

Now calculating current;
Ia= 120/90;
Ia=1.33;
Ib= j120/90;
Ib=j1.33;.

Total Current=Ia+Ib.
I=1.33+j1.33;
Converting back to polar form.
magnitude=
I= √((1.33)^2+(j1.33)^2).
I=1.76;.
θ=tan inv(1.33/1.33);.
θ=45.

So;
I=1.76<45;
Thanks; Hope it works

Given 3 phase currents; A, B, and C, we say that neutral current is equal to (A^2 + B^2 + C^2)-(AB + BC + CA).

Therefore, given 2 phase currents, A and B, netrual current is equal to (A^2 + B^2)-(AB)
Ip=Vp/Rp ==>> 120/90 = 1.3333A.

Since A=B, then neutral current is equal to (A^4)-(A^2) = A^2.
1.3333^2 = 1.7777.

There are two loads, hence the current passes through both the resistors and common Neutral

V= 120V each phase
1/R= 1/90+1/90=2/90= 1/45
R=45Ω

V = IR.
I = V/R.

Hence neutral Current
I=V/R1+V/R2
=(120/90)+(120/90).

I = 1.33+1.33 = 2.66 amp.
Or I = 120/45= 2.66 Amp.

Whereas Generator is two-phase so the Neutral Current is
IN = I * (difference in Phase angle/Total +ve angle)
the difference in phase=120.

Total angle start from zero then high and zero=180
= 2.66 * (120/180).

It is simple question since, two phase generator is connected to two load resistor therefore resistance = 90 * 90 = 8100 & total voltage = 120 * 120 = 14400.

Therefore required current through common neutral line is = 14400/8100 = 1.77A.

Give me the correct explanation!

There is the two phase.

120*120 = 14400 volt.

90*90 = 8100 ohm.

Hence current (i) = v/r.

= 14400/8100 = 1.77 amp.

V = IR.
Total resistance of two resistors(is parallel) is:

45ohms,
Voltage is 120v,
Current is =120/45,
Current is 2.66 amps.

The circuit will be balanced due to the same amount of load on both phases and so the current through the neutral wire must be zero.

@Mr Parveen Kumar and Mr Sandeep Wasnik:

Although your ideas were wrong, but I think you people even don't know how to calculate phase to phase voltage, if you don't know please keep quiet, don't post wrong things.

Whether the load is in series or parallel.