# Power Formulas in DC, AC Single Phase & Three Phase Circuits.

## Power Formulas in DC, AC Single Phase and AC Three Phase Circuits

Back to basic, below are the simple Power formulas for Single Phase AC Circuit, Three Phase AC Circuits and DC Circuits. You can easily find electric power in watts by using the following power formulas in electric circuits.

### Power Formulas in DC Circuits

• P = V x I
• P = I2 x R
• P = V2 / R

Where:

P = Power in Watts

V = Voltage in Volts

I = Current in Amperes

R = Resistance in Ohms (Ω)

### Power Formulas in Single Phase AC Circuits

• P = V x I x Cos Ф
• P = I2 x R x Cos Ф
• P = V2 / R (Cos Ф)

Where:

P = Power in Watts

V = Voltage in Volts

I = Current in Amperes

R = Resistance in Ohms (Ω)

Cos Ф = Power Factor

### Power Formulas in Three Phase AC Circuits

• P = √3 x VL x IL x Cos Ф
• P = 3 x VPh x IPh x Cos Ф
• P = 3 x I2 x R x Cos Ф
• P = 3 (V2 / R) x Cos Ф

Where:

P = Power in Watts

V = Voltage in Volts

I = Current in Amperes

R = Resistance in Ohms (Ω)

Cos Ф = Power Factor

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### Electrical Technology

1. Naeem Shaukat says:

sir i want to know in detail about KVA

2. Anonymous says:

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3. Mohammed Shiyas says:

1. Electrical Technology says:
4. M.Qasim says:

Dear sir,

5. aman kumar says:

sir i want to know about single phase circuit. pls help me.

6. Arsalan Abbas says:

dear i want to know about, why we rated prim-mover in MW (Mega-Watt) while our Generator rated in KVA………please tell me>.

this Answer KVA*.8=KW And KW/1000= Mega Watt

2. MOHAMED IQBAL MOOSA says:

The out put of the Generator will change depending on the load power factor ,0.8, 0.9 or unity power factor which is only in lighting load also if capacitance load is their the KW OR MEGA WATT WILL BE MORE.

7. Divyesh gohil says:

In 45 kw ac drive, output motor consumes 30kw, then another how much dc current use in dc bus.
Means what is the formula od dc current.

8. Sunil says:

Formula P=(I^2)*(R)*Cos(A) is wrong. Currect answer is P=(I^2)*R.

P=3*(I^2)*(R)*Cos(A) is wrong. Currect answer is P=3*(I^2)*R.

9. Carter.Abraham says:

When there is no retreat, the potential will be exerted.

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