# Math Help: Multiplying Zeq and I for Transformer - Quick and Easy Tips

• yuenkf
In summary, to multiply Zeq (0.140 + j 0.532) with I (8.7 /_ -36.87 ' ) A, first convert Zeq to polar form by finding its modulus and phase angle. Then, multiply Zeq and I together by multiplying their moduli and adding their phase angles. The result is 3.75 + j 2.97.

#### yuenkf

for transformer , Zeq multiply with I .. let say the Zeq is ( 0.140 + j 0.532 ) , while I is ( 8.7 /_ -36.87 ' ) A ... -36.87 is degree.. how to multiply these two things up? please help me . i m in urgent.. thanks.. please...

yuenkf said:
for transformer , Zeq multiply with I .. let say the Zeq is ( 0.140 + j 0.532 ) , while I is ( 8.7 /_ -36.87 ' ) A ... -36.87 is degree.. how to multiply these two things up? please help me . i m in urgent.. thanks.. please...
Convert Zeq to polar form first.

Since Z = x + j y, the modulus2 = x2 + y2 and the phase angle is the arctan (y / x)

For Zeq = 0.140 + j 0.532,

the modulus2 = 0.1402 + 0.5322 = 0.3026; modulus = 0.550
the phase angle is then arctan (0.532 / 0.140) =arctan (3.80) = 75.26° (1st. quadrant), thus

Zeq = 0.140 + j 0.532 = 0.550 ∠ 75.26°

I = 8.7 ∠ -36.87°

Zeq * I = 0.550 * 8.7 ∠ 75.26° - 36.87° = 4.785 ∠ 38.39° = 3.75 + j 2.97

thanks much.. appreciate it...

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