Different Types of DC Generator and their Circuit diagrams

The Classification of dc machine is divided by their field excitation. The field of excitation gives different characteristics. Because of different types of connections between field winding and Armature.

You may ask a question, why this field excitation configurations gives types of dc machine?

From the emf equation of the dc generator we can say,

E=NՓPZ/60A

The generated voltage E is directly proportional to the speed of the dc machine. The term RPM is related with the field current. Because of electromagnetic induction, rate of change of flux is proportional to the induced emf.

The basic two divisions of generator are

Self excited dc generator
separately excited dc generator

Again, self excitation is classified into

Series generator
shunt generator
compound generator

The compound generator is again classified into

Long shunt generator
Short shunt generator

Each generator has its own open circuit or magnetization characteristics and load or terminal characteristics.

Separately excited dc machine

As you guess, the name separately excited says that the field winding is excited with separate external power supply. There is no electrical connection between the armature and field winding the circuit diagram is shown below.

from the circuit diagram, we can write the kvl and kcl equation

Vt = Ea - IaRa

Ia=IL

The Load current is equal to the armature current. The brush drop is neglected.

Vt- Terminal voltage

Ea- Generated voltage

Ia- Armature current

Ra- Armature resistance

The separately excited machine is used for supply source to the speed control of dc motor.

Series generator

In this machine, the field winding is connected in series with armature. so, the load current is equal to the armature current.

By kvl, the equation,

Vt = Ea - Ia(Ra+Rse)

Ia=IL=Ise

Ise - Series current

Rse-series field resistant

In this type of machine is used in demand of load current supply.

Shunt generator

The word shunt means that field winding is connected in parallel with armature. As you can see in the circuit diagram the armature current is divided in to load current and shunt field current.

Vt = Ea - IaRa

Ia=IL + Ish

The voltage regulation of shunt generator is high. because the no load to full load voltage is almost constant. Therefore, it is used in electro-plating and battery charging applications.

Compound generator

There are two windings present inside the compound generator one is series field another one is shunt field.

If the series magnetic field aids the shunt magnetic field then its is called as cumulative mode.

If the series magnetic field opposes the shunt magnetic field then it is called as differential mode.