Back EMF of DC Generator Calculator

✖Output Voltage is the electrical potential difference between the two terminals of the dc machine. Output Voltage is also called the Terminal Voltage.ⓘ Output Voltage [V_o]			+10% -10%
✖Armature Current is defined as the current developed in the armature of an electrical DC generator due to movement of rotor.ⓘ Armature Current [I_a]			+10% -10%
✖Armature Resistance is the ohmic resistance of the copper winding wires plus the brush resistance in a dc machine.ⓘ Armature Resistance [R_a]			+10% -10%

✖Back EMF is developed when current flows through the armature, it generates a magnetic field that interacts with the field produced by the field winding to produce a torque.ⓘ Back EMF of DC Generator [E_b]

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Formula

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Back EMF of DC Generator

Formula

`"E"_{"b"} = "V"_{"o"}-("I"_{"a"}*"R"_{"a"})`

Example

`"90V"="150V"-("0.75A"*"80Ω")`

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Back EMF of DC Generator Solution

STEP 0: Pre-Calculation Summary

Formula Used

Back EMF = Output Voltage-(Armature Current*Armature Resistance)
E_b = V_o-(I_a*R_a)
This formula uses 4 Variables

Variables Used

Back EMF - (Measured in Volt) - Back EMF is developed when current flows through the armature, it generates a magnetic field that interacts with the field produced by the field winding to produce a torque.
Output Voltage - (Measured in Volt) - Output Voltage is the electrical potential difference between the two terminals of the dc machine. Output Voltage is also called the Terminal Voltage.
Armature Current - (Measured in Ampere) - Armature Current is defined as the current developed in the armature of an electrical DC generator due to movement of rotor.
Armature Resistance - (Measured in Ohm) - Armature Resistance is the ohmic resistance of the copper winding wires plus the brush resistance in a dc machine.

STEP 1: Convert Input(s) to Base Unit

Output Voltage: 150 Volt --> 150 Volt No Conversion Required
Armature Current: 0.75 Ampere --> 0.75 Ampere No Conversion Required
Armature Resistance: 80 Ohm --> 80 Ohm No Conversion Required

STEP 2: Evaluate Formula

Substituting Input Values in Formula

E_b = V_o-(I_a*R_a) --> 150-(0.75*80)

Evaluating ... ...

E_b = 90

STEP 3: Convert Result to Output's Unit

90 Volt --> No Conversion Required

FINAL ANSWER

90 Volt <-- Back EMF

(Calculation completed in 00.004 seconds)

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Home » Engineering » Electrical » Machine » DC Machines » DC Machine Characterstics » Back EMF of DC Generator

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Created by Urvi Rathod

Vishwakarma Government Engineering College (VGEC), Ahmedabad

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< 16 DC Machine Characterstics Calculators

Mechanical Efficiency given Induced Voltage and Armature Current

Go Mechanical Efficiency = (Electrical Efficiency*Output Voltage*Armature Current)/(Angular Speed*Torque)

Electrical Efficiency of DC Machine

Go Electrical Efficiency = (Mechanical Efficiency*Angular Speed*Torque)/(Output Voltage*Armature Current)

Design Constant of DC Machine

Go Machine Constant = (Number of Conductors*Number of Poles)/(2*pi*Number of Parallel Paths)

Angular Speed of DC Machine using Kf

Go Angular Speed = Armature Voltage/(Machine Constant*Magnetic Flux*Armature Current)

Armature Induced Voltage of DC Machine given Kf

Go Armature Voltage = Machine Constant*Armature Current*Magnetic Flux*Angular Speed

Back EMF of DC Generator

Go Back EMF = Output Voltage-(Armature Current*Armature Resistance)

Magnetic Flux of DC Machine given Torque

Go Magnetic Flux = Torque/(Machine Constant*Armature Current)

EMF Generated in DC Machine with Lap Winding

Go EMF = (Rotor Speed*Number of Conductors*Flux per Pole)/60

Torque generated in DC Machine

Go Torque = Machine Constant*Magnetic Flux*Armature Current

Coil Span of DC Motor

Go Coil Span Factor = Number of Commutator Segments/Number of Poles

Front Pitch for DC Machine

Go Front Pitch = ((2*Number of Slots)/Number of Poles)-1

Back Pitch for DC Machine

Go Back Pitch = ((2*Number of Slots)/Number of Poles)+1

Input Power of DC Motor

Go Input Power = Supply Voltage*Armature Current

Pole Pitch in DC Generator

Go Pole Pitch = Number of Slots/Number of Poles

Back Pitch for DC Machine given Coil Span

Go Back Pitch = Coil Span*Coil Span Factor

Output Power of DC Machine

Go Output Power = Angular Speed*Torque

Back EMF of DC Generator Formula

Back EMF = Output Voltage-(Armature Current*Armature Resistance)
E_b = V_o-(I_a*R_a)

How does back EMF affect supply voltage?

As the back emf depends on the current their value also decreases. The magnitude of the back EMF is nearly equal to the supply voltage. If the sudden load is applied to the motor, the motor becomes slow down. As the speed of the motor decreases, the magnitude of their back emf also falls down.

How to Calculate Back EMF of DC Generator?

Back EMF of DC Generator calculator uses Back EMF = Output Voltage-(Armature Current*Armature Resistance) to calculate the Back EMF, The Back EMF of DC Generator is defined as the opposition offered the supply voltage. The supply voltage induces the current in the coil which rotates the armature. The electrical work required by the motor for causing the current against the back emf is converted into mechanical energy. Back EMF is denoted by E_b symbol.

How to calculate Back EMF of DC Generator using this online calculator? To use this online calculator for Back EMF of DC Generator, enter Output Voltage (V_o), Armature Current (I_a) & Armature Resistance (R_a) and hit the calculate button. Here is how the Back EMF of DC Generator calculation can be explained with given input values -> 90 = 150-(0.75*80).

FAQ

What is Back EMF of DC Generator?

The Back EMF of DC Generator is defined as the opposition offered the supply voltage. The supply voltage induces the current in the coil which rotates the armature. The electrical work required by the motor for causing the current against the back emf is converted into mechanical energy and is represented as E_b = V_o-(I_a*R_a) or Back EMF = Output Voltage-(Armature Current*Armature Resistance). Output Voltage is the electrical potential difference between the two terminals of the dc machine. Output Voltage is also called the Terminal Voltage, Armature Current is defined as the current developed in the armature of an electrical DC generator due to movement of rotor & Armature Resistance is the ohmic resistance of the copper winding wires plus the brush resistance in a dc machine.

How to calculate Back EMF of DC Generator?

The Back EMF of DC Generator is defined as the opposition offered the supply voltage. The supply voltage induces the current in the coil which rotates the armature. The electrical work required by the motor for causing the current against the back emf is converted into mechanical energy is calculated using Back EMF = Output Voltage-(Armature Current*Armature Resistance). To calculate Back EMF of DC Generator, you need Output Voltage (V_o), Armature Current (I_a) & Armature Resistance (R_a). With our tool, you need to enter the respective value for Output Voltage, Armature Current & Armature Resistance and hit the calculate button. You can also select the units (if any) for Input(s) and the Output as well.

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