What is critical resistance of DC generator?
The critical field resistance is defined as the maximum field circuit resistance (for a given speed) with which the shunt generator would just excite. The shunt generator will build up voltage only if field circuit resistance is less than critical field resistance.
How do you find the critical resistance of a DC generator?
Generally data for plotting the open circuit characteristics is given. Plot the characteristics on the graph paper to the scale. Draw the tangent, to the initial part of this O.C.C. then the slope of this line is the critical resistance for the speed at which the data is given.
What is critical speed of a DC shunt generator also explain the condition for voltage development?
This speed n2 is hence called Critical Speed. Thus Critical Speed is that speed at which the DC Shunt Generator just fails to buil up voltage with no external resistance in the field circuit.
What is rated speed of DC generator?
The speed rating of a DC generator is the rated speed at which the machine should be operated which is specified in revolutions per minute (R.P.M or r/min). The machine is required to be operated at a rated speed in order to deliver the rated power at the rated voltage.
How do DC generators work?
Working principle of a DC generator: In a DC generator, field coils produce an electromagnetic field and the armature conductors are rotated into the field. Thus, an electromagnetically induced emf is generated in the armature conductors. The direction of induced current is given by Fleming’s right hand rule.
When two DC generators are running in parallel an equalizer bar is used?
When two D.C. series generators are running in parallel, an equalizer bar is used. A. To increase the speed and hence generated e.m.f.
How can the speed of a DC motor be controlled?
Thus, the speed of a DC motor can control in three ways: By varying the flux, and by varying the current through field winding. By varying the armature voltage, and the armature resistance. Through the supply voltage.
What are the 3 types of DC motors?
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.
Is DC motor and DC generator same?
DC motor and DC generator are similar from the mechanical perspective, however from a technical stand point, both differ from each other significantly. DC motor converts electrical energy into mechanical energy whereas DC generator converts mechanical energy into an electrical energy.
What are the advantages of DC generator?
From what you read above, we can say that the main advantages of DC generators include simple design, simple parallel operation, and fewer problems of system stability. You also read about different types of DC generators and their working principle.
What does DC generator do?
A DC generator is the type of electrical generator that converts mechanical energy into direct current electricity. Here, energy conversion is based on the principle of dynamically induced EMF production. These generators are most suitable for off-grid applications.
What is Equalizer bar in DC generator?
A conductor of low resistance known as “Equalizer Bar” is connected between the two armature ends of two generators as shown in the figure. The operation of the equalizing bar is to make an equal flow of field currents in two generators series field coils.
How can we increase the rpm of dc motor?
How to improve torque and RPM of a DC motor?
- Case 1: Increase/Decrease strength of permanent magnets. What would happen to torque and RPM?
- Case 2: Increase/Decrease size of magnet wires.
- Case 3: Increase/Decrease the size of armature.
- Case 4: Increase/Decrease the number of turns (coil).
Which is best AC or DC motor?
Which Motor Is More Powerful: AC or DC? AC motors are generally considered to be more powerful than DC motors because they can generate higher torque by using a more powerful current. However, DC motors are typically more efficient and make better use of their input energy.
Can a DC motor become a generator?
Any DC motor with permanent magnets can easily be a generator. It doesn’t matter whether it is brushed or not; brushless motors make great generators but you will need to add a rectifier to get a DC output.
What are disadvantages of DC generator?
Like other machines, DC generators have some disadvantages, such as: DC generators can’t be applied to a transformer. DC generators have low efficiency because there are copper losses, eddy current losses, hysteresis losses, and mechanical losses. A voltage drop over long distances would occur.