Separately Excited Dc Generator

A separately excited DC generator is the one whose field winding is supplied by an independent external DC source (like a battery). The magnitude of generated voltage depends upon the speed of rotation of armature and the field current, i.e., greater the speed and the field current, higher is the generated voltage.

What are separately excited generators used for?

Applications of Separately Excited DC Generators These are able to produce a wide range of voltage output, they are primarily used in laboratory and commercial testing. These are used in speed regulation tests. These generators operate in a stable condition with any change in field excitation.

What is separately excited?

Definition of separately excited : having the field magnets excited by a current from a separate source —used of a machine.

What are the advantages & disadvantages of a separately excited DC generator?

Separately excited DC generators have distinct advantages over self-excited DC generators. It can operate in stable condition with any field excitation and gives wide range of output voltage. The main disadvantage of these kinds of generators is that it is more expensive to provide a separate excitation source.

Why it is called separately excited DC motor?

A separately excited dc motor is a motor whose field circuit is supplied from a separate constant-voltage power supply, while a shunt dc motor is a motor whose field circuit gets its power directly across the armature terminals of the motor.

What is the advantage of separately excited DC motor?

Separately excited DC motor can operate above the base speed in the field-weakening region by reducing the field current independently. Also its speed direction can be reversed by reversing the armature voltage.

What is the difference between self excited and separately excited DC generator?

Based on the method of excitation dc generators can be divided into two groups. In a separately excited (S.E.) machine, the field winding is connected to a separate voltage source while, in a self excited generator field winding is connected across the armature terminals (provides its exciting current) .

What are types of DC generator?

DC generators are mainly categorised into three types based on the field excitation methods. They are Permanent Magnet DC generator, Separately Excited DC generator, and Self-Excited DC generator.

What is the working principle of a DC generator?

A DC generator operates on the principle of Faraday's laws of electromagnetic induction. According to Faraday's law, whenever a conductor is placed in a fluctuating magnetic field (or when a conductor is moved in a magnetic field) an EMF is induced in the conductor.

What are the 3 types of self excited DC generator explain each?

There are three methods of excitation, and thus three main types of DC generators: Permanent Magnet DC Generators – Field coils excited by permanent magnets. Separately Excited DC Generators – Field coils excited by some external source. Self Excited DC Generators – Field coils excited by the generator itself.

How can you control the speed of a separately excited DC motor?

The speed of separately excited dc motor can be control by changing the armature voltage and changing field flux. Due to this the speed can be controlled for below rated speed and speed above the rated speed, respectively.

What is the advantage of using separately excited generator over self excited generator?

Separately excited DC generators have many advantages over self-excited DC generators. It can operate in stable condition with any field excitation and gives wide range of output voltage. The main disadvantage of these kinds of generators is that it is very expensive of providing a separate excitation source.

What happens in a separately excited DC generator when the load is increased?

When the load supplied by the generator is increased, IL (and therefore IA) increases. As the armature current increases, the lARA drop increases, so the terminal voltage of the generator falls.

What is the no load characteristic of the separately excited DC generator?

Characteristics of separately excited DC Generator If there is no armature reaction and armature voltage drop, the voltage will remain constant for any load current. Thus, the straight line AB in above figure represents the no-load voltage vs. load current IL.

Why does the separately excited DC generator generate a voltage without any field excitation?

Separately excited DC Generator without Excitation: If the generator is run at any particular speed without field excitation, some EMF will be generated due to residual magnetism in the main poles. This power of magnetism after the applied magnetism is removed is called residual magnetism of a substance.

What are the 4 types of dc motor?

There are 4 main types of DC motors:

• Permanent Magnet DC Motors. The permanent magnet motor uses a permanent magnet to create field flux.
• Series DC Motors. In a series DC motor, the field is wound with a few turns of a large wire carrying the full armature current. ...
• Shunt DC Motors. ...
• Compound DC Motors.

What is DC shunt generator?

A shunt generator is a type of electric generator in which field winding and armature winding are connected in parallel, and in which the armature supplies both the load current and the field current for the excitation (generator is therefore self excited).

What is the difference between permanent magnet dc motor and separately excited dc motor?

The main difference between Permanent Magnet Dc Motor and other types of the motor is just the types of magnet used. In PMDC Motors, we use a pair of permanent magnets to operate it.

How many ways can you control the separately excited DC generator?

There are two Methods of Excitation of DC Generator. Shunt excitation: Here the field winding is provided with a large number of turns of thin wire and is excited from a voltage source. The field winding, therefore, has a high resistance and carries a small current.

Why does the speed of the separate excited motor decrease with increasing load?

We know that the speed of a motor is related to the back EMF/flux i.e. Eb / φ. Once the load is increased, back EMF and flux reduce because of the armature resistance reduction and armature reaction respectively. However, back EMF reduces more than flux, so that the speed of the motor slightly drops with the load.