Voltage regulation of Transformer

                                                      Voltage regulation of  Transformer.

Transformer no - load voltage and full-load conditions of voltage and full load voltage difference is ratio Voltage Regulation. The percentage rate of the ratio. Such as: -

Regulation of the voltage transformer must be less than that amount, the lower the better.

The regulation voltage transformer coil voltage detection, both with full load terminal voltage drops to the no - load voltage is determined. The no - load voltage is determined as the secondary.

 In other words,

Vp / a = Vs + Zes

Here,

Vp / a = no - load voltage secondary

Vs = secondary full-load terminal Voltage.

Is Zes = transformer coil in both the total voltage drop (secondary side)

The Vp / a = VNL and Vs = VFL in

Transformer regulation,

Vreg = VNL - VFL ÷ VFL × 100%

Vs-a reference to the

Vp / a = √ (Vs Cos θ + IsRes) ² + √ (Vs Sin θ + Is Xes) ²

Or Vs-a reference to the

Vp / a = Vs + Is (Cos θ - j Sin θ) (Res + j Xes)

Methods and equations can be used.

When, Cos θ = load power factor

If the power factor leading θ-value is negative.

 Example of mathematics & solution :-

1. 25 KVA, 2300/230 V Transformers Rp = 0.8Ω Xp = 3.2Ω, Rs = 0.009Ω, Xs = 0.03Ω equal to transformer of regulation. When -

1. Power Factor unit.

2. Power factor 0.8 lagging

3. Power factor leading 0.866.

Ans: - a = 2300/230

              = 10

Is = 25 × 1000 ÷ 230 = 108.7 A

Secondary terms

Res = Rp / a ² + Rs = 0.8 / (10) ² + 0.009 = 0.017 Ω

Xes = Xp / a ² + Xs = 3.2 / (10) ² + 0.03 = 0.062 Ω

IsRes = 108.7 × 0.017 = 1.85 V

IsXes = 108.7 × 0.062 = 6.74 V

1. V / a = VNL = √ (VFL cosθ + IsRes) ² + √ (VFLsinθ + IsXes) ²

= √ (230 + 1.85) ² + √ (0 + 6.74) ²

= 231.95 V.

Vreg = VNL - VFL ÷ VFL × 100%

= 231.95 - 230 ÷ 230 × 100%

= 0.84%

2. Here Cos θ = 0.8, Sin θ = 0.6

V / a = VNL = √ (VFL cosθ + IsRes) ² + √ (VFLsinθ + IsXes) ²

= √ (230 × 0.8 + 1.85) ² + √ (230 × 0.6 + 6.74) ²

= 235.57 V.

Vreg = VNL - VFL ÷ VFL × 100%

= 235.57 - 230 ÷ 230 × 100%

= 2.82%

3. Here Cos θ = 0.866 Sin θ = - 0.5

(Θ-'s value because of the negative power factor leading)

V / a = VNL = √ (VFL cosθ + IsRes) ² + √ (VFLsinθ + IsXes) ²

= √ (230 × 0.8 + 1.88) ² + √ (230 × (- 0.5 + 6.74) ²

= 228.32 V.

Vreg = VNL - VFL ÷ VFL × 100%

= 228.32 - 230 ÷ 230 × 100%

= - 0.73%


2. Short-Circuit Test of a 10KVA 2300/230V Transformers were found to have the following information, Ese = 137V, Psc = 192 W, Isc = 4.34A, 0.8 power factor of percent voltage regulation  lagging to out now.

Ans: -

That have been invoked

Rating = 10KVA. % Reg =   ?

Ep = 2300V Pf = 0.8 lagging

Es = 230V

Esc = 137V

Psc = 192W

Isc = 4.34A

Re = Psc / I ² sc

 = 192 / (4.34) ² = 10.19 Ω

Ze = Esc / Isc

= 137 / 4.34 = 31.57 Ω

Xe = √ Ze - √ R ² e

= √ (31.57) - √ (10.19) ²

= 29.88 Ω

I = KVA × 1000 / Ep

= 10 × 1000/2300

= 4.35A

IRe = 4.35 × 10.19 = 44.3V

IXe = 4.35 × 29.98 = 129.98V

Cosθ = 0.8 & sinθ = 0.6

Vp = √ (V cosθ + IRe) ² + √ (Vsinθ + IXe) ²

= √ (2300 × 0.8 + 44.3) - √ (2300 × 0.6 + 129.98) ²

= 2414.8 V

Vreg = VNL - VFL ÷ VFL × 100%

= 2414.8 - 2300 ÷ 2300 × 100%

= 4.99%