I am using DC permanent magnet motor as a DC generator. I would like to calculate the estimated output voltage and current from the generator at known speeds. I already know the armature resistance and inductance for the motor. Do you know where can I find the equation?

Many thanks

i think this may help you

1) Separately exicted

2) DC shunt excitation

3) DC series excitation

4) DC componund excitation

DC permagnet is considered as equivalent to dc separately excited motor

considering the magnetism of magnet does not deteriorate with passage of time ( but it do go down with time) you can apply the equations for separately excited.

As NM mentioned..

resistance and inductance can be calculated from v and I equations

I can be known from ammeter which is connected at output side

We use the equation for generator

E (induced emf) = Vt(terminal voltage) + Ia * ra

Where E is directly proportional to speed

E = K w

W= speed of rotor

K can be found out from no of conductors parallel path and other parameters

Let me know if problem persists

@mibawad: yes freak is right there is no concept of inductance in DC machines

inductance and capacitance only appears in AC machines because there is no alternating current in DC machines

inductance only appears at only there is a existence of alternating current

What I want to say that for DC motor or generator:

Emf=V+Ia*Ra+La(di/dt)

Emf=K*w

If I know K, w, Ra and La, and I want to calculate V and I according to the speed w. I couldn't from this equation because the number of unknown is more than the number of equations.

And you need to know amout the load somehow..

you cant absolutely..

E=V+(I*R)

there is no inductance

Therefore, I couldn't calculate the current and voltage generated from the DC generator without knowing the load as well. Is that what do you want to say?

Yes buddy.. i am saying the same thing..

And without knowing supply voltage as well as load no engineer of world can do it..

Kidding😎

which produces Reactance Voltage.

Fi - flux

Z - no. Of conductors

P - parallel paths

A - its value depends on winding. Eg: 2 for a simplex winding

This is the induced EMF. To get the terminal voltage the armature copper loss is subtracted. (Assuming its seperately excited)

https://www.learnelectrical.net/2015/07/emf-equation-of-dc-generator.html

An equation which popped up in my mind is:

EMF equation of Generator-

** Eg = PΦNZ / 60A**

Here,

P = No. of field poles

Φ = Flux produced per mole

Z = No. of armature conductors

A = No. of parallel paths in the armature

N = Rotational speed of the armature (rpm)

Torque equation of Generator-

1) Armature Torque(Ta)-

** Ta = (PZ / 2πA) × Φ.Ia (N-m) **

In this equation, the term (PZ / 2πA) is constant. That means Torque of the armature is directly proportional to the product of magnetic flux(Φ ) and the current flowing in the armature(Ia).

2) Shaft Torque(Tsh)-

**Tsh = output in watts / (2πN/60)**

@Akshay, You can go through the EMF equation of Generator to increase the number of rotations(rpm) in generator.

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