## Electric Breaking of DC Motors – Types of Electric Breaking

Manish Kumar Saini

Updated on 16-Aug-2021 09:00:31

The DC motors can be stopped using one of the following methods −Mechanical (Friction) BreakingElectric BreakingIn mechanical breaking, the motor is stopped due to friction between the moving parts of the motor and the break shoe. The mechanical breaking has several disadvantages as non-smooth stop, wear and tear of moving ... Read More

## Efficiency of a DC Motor – Condition for Maximum Efficiency

Manish Kumar Saini

Updated on 16-Aug-2021 08:21:09

Efficiency of a DC MotorThe efficiency of a DC motor is defined as the ratio of output power to the input power.Mathematically, $$\mathrm{Efficiency, \eta \:=\:\frac{Power\:Output}{Power\:Intput}\times 100 \%\:=\:\frac{P_{out}}{P_{in}}\times100\%\:...(1)}$$Since, $$\mathrm{Power\:input, \:P_{in} = Power\:Output(P_{out}) + Losses}$$Therefore, $$\mathrm{Efficiency, \eta \:=\:\frac{P_{out}}{P_{out}\:+\:losses}\times100\%\:....(2)}$$Condition for Maximum Efficiency of DC MotorThe efficiency of a DC motor is not constant ... Read More

## What is an Autotransformer?

Manish Kumar Saini

Updated on 14-Aug-2021 11:35:32

An autotransformer is a one winding transformer in which a part of the winding is common to both primary and secondary windings.An autotransformer has a single continuous winding with a tap point between the primary and secondary windings. The tap point can be adjusted to obtain the desired output voltage, ... Read More

## What is a Current Transformer?

Manish Kumar Saini

Updated on 14-Aug-2021 11:33:11

A current transformer (C.T.) is an instrument transformer which is used for the protection and measurement purposes in a power system. The C.T. is primarily used to measure high alternating currents in a power system.Construction of Current TransformerThe magnetic core of the current transformers is made up of thin laminations ... Read More

## Transformer No-Load Current Wave Shape Considering Core Loss

Manish Kumar Saini

Updated on 14-Aug-2021 11:30:59

A transformer needs less magnetic material if it is operated at a higher core flux density. Thus, from the economic point of view, a transformer is designed to operate in the saturation region of the magnetic core.When a sinusoidal voltage is applied to the primary winding of the transformer, then ... Read More

## Transformer Inrush Current – Calculation and Theory

Manish Kumar Saini

Updated on 14-Aug-2021 11:26:18

There is a sudden inrush of the primary current, when the transformer is initially energized and the maximum value of the magnetic flux is more than twice the normal value of the flux. Hence, due to the very high peak of the magnetising current, the core is driven far into ... Read More

## Three-Phase Transformer Vector Groups – How are the Vector Groups Divided?

Manish Kumar Saini

Updated on 14-Aug-2021 11:16:41

The three-phase transformer vector groups are divided into four main groups depending on the phase difference between the corresponding line voltages on the high-voltage and lowvoltage sides. The angle by which the line voltage on the low-voltage side lags behind the line voltage on the high-voltage side is called as ... Read More

## Working Principle of a Three-Phase Transformer

Manish Kumar Saini

Updated on 14-Aug-2021 11:13:30

A three phase transformer is required to step-up or step-down the three phase voltages in a power system. The 3-phase transformers can be constructed in one of the following ways −Three separate 1-phase transformers can be connected for the 3-phase operation. Such an arrangement is known as 3-phase bank of ... Read More

## Three-Phase to Twelve-Phase Transformers: Circuit Diagram and Phasor Diagram

Manish Kumar Saini

Updated on 14-Aug-2021 11:10:08

The circuit arrangement of the transformers for three-to-twelve phase transformation is shown in the figure.Here, two banks of three 1-phase transformers or two 3-phase transformers are required. In this connection, the secondary windings are arranged in the form of pair of double-star connections. The primary windings of one set of ... Read More

## Testing of Transformer | Type Tests, Routine Tests and Special Tests of Transformer

Manish Kumar Saini

Updated on 14-Aug-2021 11:04:20

An electrical transformer is tested at the transformer manufacturer premises and at the consumer’s site and also periodically in regular and emergency basis during its service life to confirm its specifications and performance.Types of Transformer TestsTests of transformer done at the manufacturer’s premises −Type testsRoutine testsSpecial testsTests of transformer done ... Read More