What is the purpose of using field rheostat in the DC shunt motor experiment?

What is the purpose of using field rheostat in the DC shunt motor experiment?

Answer: At the time of starting of motor, the armature resistance is kept at maximum position to control and reduce the high starting current and field rheostat atminimum position to ensure that speed does not go beyond rated value and to have high starting torque.

Why a starting rheostat was used for the prime mover motor?

Since there is no counter emf when the armature is at a standstill, the current taken by the armature will be abnormally high. As a result, the armature current must be limited by an external resistor, such as a starting rheostat.

What is the use of rheostat in DC shunt generator?

OUTPUT VOLTAGE CONTROL Field rheostats are used to control the voltage output of shunt generators. At a given speed, the rheostat can be used only to bring the output voltage to values below the rated voltage obtainable without a field control.

What does happen when field rheostat gets opened in running condition in DC motor?

As mentioned above if the field circuit is opened, the back emf will drop to zero. With full armature voltage applied this will cause a very large armature current to flow which should normally blow the fuses. In this case the motor will accelerate and run away until the fuses blow.

What is the relationship between flux and speed of the DC shunt motor?

Flux control method It is already explained above that the speed of a dc motor is inversely proportional to the flux per pole. Thus by decreasing the flux, speed can be increased and vice versa. To control the flux, a rheostat is added in series with the field winding, as shown in the circuit diagram.

Is motor a prime mover?

The word “motor” refers to any power unit that generates motion, that is a “prime mover”, while “electric motor” refers to a “prime mover using electricity.” An electric motor is a device used to convert electrical energy into mechanical energy.

What is the difference between AC and DC motors?

The most obvious difference is the type of current each motor turns into energy, alternating current in the case of AC motors, and direct current in the case of DC motors. AC motors are known for their increased power output and efficiency, while DC motors are prized for their speed control and output range.

Why do we use 3 point starter in DC shunt motor?

A three-point starter is an electrical device, used for starting as well as maintaining the DC shunt motor speed. The connection of resistance in this circuit is in series which decreases the initial high current and guards the equipment against any electrical failures.

What are the applications of DC shunt motor depending on its characteristics?

DC Shunt Motor Applications

• These motors are used wherever stable speed is required.
• This kind of DC motor can be used in Centrifugal Pumps, Lifts, Weaving Machine, Lathe Machines, Blowers, Fans, Conveyors, Spinning machines, etc.

Can a rheostat completely block the current flow?

Rheostat reduces the electric current flow to certain level. However, it does not completely blocks the electric current flow. To completely block the electric current flow, we need infinite resistance.

How is the minimum resistance achieved in rheostat?

If we use the terminals B and C, the minimum resistance is achieved when we move the slider or wiper close to the terminal C, because the length of the resistive path decreases. As a result, only a small amount of electric current is blocked and large amount of electric current is allowed.

Where does the word rheostat come from in science?

The English scientist Sir Charles Wheatstone coined the word rheostat, it is derived from the Greek word “rheos” and “-statis” which means a stream controlling device or a current controlling device.

Which is the international standard symbol for rheostat?

The zigzag lines with three terminals represent the American standard symbol of rheostat and the rectangular box with three terminals represents the international standard symbol of rheostat. Types of rheostats. Rheostats are of two types: Rotary rheostats; Linear rheostats