 Motors

# Voltage And Power Equations of a DC Motor

## Voltage And Power Equations of a DC Motor

Voltage Equation of the DC Motor
Input Voltage provided to the motor armature can perform the following two tasks:
Obtain control on Back E.M.F Eb of the Motor.
Provide supply to the Ohmic IaRa drop.
i.e.

V = Eb + IaRa ………………….(1)

Where
Eb = Back E.M.F
IaRa   = Armature Current  X  Armature Resistance
This is called “Voltage Equation of the DC Motor”.
Power equation of a DC Motor
Multiply both sides of Equation (1) by Ia , we get,

VIa= EbIa +Ia2Ra ………. (2)

where,
VIa = Input Power supply (Armature Input)
EbIa = Mechanical Power developed in Armature (Armature Output)

Ia2Ra= Power loss in armature (Armature Cupper (Cu) Loss)

### Electrical Technology

1. Ganesh says:

Hello sir I want the full equation…..

2. R.J.Jochems says:

In the article “Voltage And Power Equations of a DC Motor” the iron losses are not mentioned.
Those losses can not be neglected.
Would be interesting to see those incorporated in the calculations.

3. R.Prabhakar Rao says:

I need power knowledge for the selection of motors and VFD.

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