# What is the residual voltage?

The residual voltage is the voltage that remains in an output transistor while it is ON. For example, consider an NPN output with a power supply voltage of 24 V and a residual voltage of 2 V. While the output transistor is ON, there will be 2 V between the output line (the black wire) and the 0-V line (the blue wire).

Subsequently, one may also ask, what do you mean by residual voltage of LVDT?

Differencing the two secondary voltages results in “zero” output volts. This is the null position of the LVDT. In reality, there is a small residual voltage left due to factors like winding capacitance and variances in the magnetic materials.

## What is the function of residual voltage transformer?

Residual Voltage Transformers (RVT)are a type of instrument transformers that are used for protecting capacitor banks from earthing faults in an electrical system. Their primary function is to detect neutral to ground fault conditions and discharge capacitor banks.

## What do you mean by residual flux?

In the magnetic hysteresis loops showing the magnetic characteristics of a material, the remanence is the value of the flux density remaining when the external field returns from the high value of saturation magnetization to 0. The remanence is also called the residual magnetization.

## What do you mean by residual magnetism?

Remanence or remanent magnetization or residual magnetism is the magnetization left behind in a ferromagnetic material (such as iron) after an external magnetic field is removed. It is also the measure of that magnetization. Colloquially, when a magnet is “magnetized” it has remanence.

## What is the critical resistance?

The critical field resistance is defined as the maximum field circuit resistance (for a given speed) with which the shunt generator would excite. The shunt generator will build up voltage only if field circuit resistance is less than critical field resistance.

## How does the commutator converts AC to DC?

The commutation in DC machine or more specifically commutation in DC generator is the process in which generated alternating current in the armature winding of a dc machine is converted into direct current after going through the commutator and the stationary brushes.

## What is critical speed and critical resistance?

The critical field resistance is defined as the maximum field circuit resistance (for a given speed) with which the shunt generator would excite. The shunt generator will build up voltage only if field circuit resistance is less than critical field resistance.

## What do you mean by critical speed?

In solid mechanics, in the field of rotordynamics, the critical speed is the theoretical angular velocity that excites the natural frequency of a rotating object, such as a shaft, propeller, leadscrew, or gear.

## Which type of starter is used to start the DC motor?

A 3 point starter is used for starting a DC shunt motor. A 4 point starter is used for starting a DC compound wound motor.

## Why is the current drawn by a DC motor so high at starting?

The starting current is high as there is no back EMF or counter EMF present in the armature circuit because at starting counter EMF is zero. It’s armature has very less resistance due to this it need more current at starting time. Hence DC starters are used to limit the starting current of motor.

## Why do we need a starter in DC motor?

The starter protects the armature of dc motor from getting damaged. As the speed of armature/motor build up, armature induced emf also starts building thus reducing the role resistance offered by the starter, hence requiring it to gradually reduce as the motor picks up full speed.

## Why do we need a starter?

In dc motors the armature is generally designed to have the least resistance possible. So when starting a dc motor starter is connectedsuch that it limits the current value by being in series with armature and later seperates from the circuit. But by then back emf develops in the armature.

## What is the use of 3 point starter?

A 3 point starter in simple words is a device that helps in the starting and running of a shunt wound DC motor or compound wound DC motor. The back emf, develops as the motor armature starts to rotate in presence of the magnetic field, by generating action and counters the supply voltage.

## What is the use of 4 Point starter?

Working Principle of Four Point Starter. The 4 point starter like in the case of a 3 point starter also acts as a protective device that helps in safeguarding the armature of the shunt or compound excited DC motor against the high starting current produced in the absence of back emf at starting.

## Why a single phase induction motor is not self starting?

Rotating magnetic field, there are minimum two phases required. But in the case of single phase induction motor, there is a single phase. Hence, not self starting. When stator winding of a Single Phase Induction Motor is connected to a sinusoidally alternating voltage source, the stator flux alternates in a space.

## Why the synchronous motor is not self starting?

This is because the speed with which rotating magnetic field is rotating is so high that it is unable to rotate the rotor from its initial position, due to the inertia of the rotor. So under any case, whatever may be the starting position of the rotor, synchronous motor is not self starting.

## Is single phase motor self starting?

Single-phase induction motors are not self-starting without an auxiliary stator winding driven by an out of phase current of near 90o. Once started the auxiliary winding is optional. The auxiliary winding of a permanent-split capacitor motor has a capacitor in series with it during starting and running.

## Why the induction motor is self starting?

Consider a 3-phase induction motor: A 3- phase supply to the armature produces a rotating magnetic field. This flux being linked to the rotor coils, induces voltage and produces current in the rotor. The current carrying rotor being placed in a magnetic field, experiences a torque and hence begins to rotate.

## Why does a single phase motor need a capacitor?

A motor capacitor, such as a start capacitor or run capacitor (including a dual run capacitor) is an electrical capacitor that alters the current to one or more windings of a single phase AC induction motor to create a rotating magnetic field.

## Why capacitors are used?

Power conditioning. Reservoir capacitors are used in power supplies where they smooth the output of a full or half wave rectifier. They can also be used in charge pump circuits as the energy storage element in the generation of higher voltages than the input voltage.

## How do capacitors typically fail?

At higher temperature and higher voltage, the capacitors will fail more quickly. The temperature can be influenced by dust and debris (insulating the capacitor) in the compressor unit. Electrolytic capacitors are more sensitive to temperature and have a propensity to expand, causing premature failure.

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