What is brush drop?

It is the power loss at the brush contact point. The brush drop depends upon the brush contact voltage drop and the armature current Ia. It is given by the equation shown below: The voltage drop occurring over a large range of armature currents, across a set of brushes is approximately constant.

How do you reduce brush losses?

Clean bearings and proper lubrication are essential to the reduction of bearing friction. Brush friction is reduced by assuring proper brush seating, using proper brushes, and maintaining proper brush tension. A smooth and clean commutator also aids in the reduction of brush friction.

What are the types of losses in DC machine?

The losses in the dc machine are mainly separated into five categories like electrical/copper, magnetic/core/iron, brush, mechanical, and stray.

What is stray losses in DC machine?

According to this standard, the stray load losses 1n d.c. machinery are defined as the sum of the following par- tial losses: (1) Additional core loss due to the flux from arma- ture windings excited by load current (2) Eddy currents in the armature windings (3) Short circuit loss of commutation.

What are mechanical losses?

Mechanical losses occur in the moving parts of the DC machine due to friction and windage. These losses are also called rotational losses. The mechanical losses depend upon the speed of the machine.

L3 Types of DC machines and EMF equation of DC Machine

What are the 2 main types of losses in a motor?

Intrinsic losses are of two types: fixed losses - independent of motor load, and variable losses - dependent on load. Fixed losses consist of magnetic core losses and friction and windage losses. Magnetic core losses (sometimes called iron losses) consist of eddy current and hysteresis losses in the stator.

What is eddy current loss?

If an eddy current of magnitude I flows through a core path of resistance r, it will dissipate energy in the form of heat according to the power equation power = I2R. Since this represents energy being expended for no useful purpose, it is considered as an eddy current loss, sometimes called iron loss.

What is windage loss?

Windage loss is the reduction in efficiency due to windage forces. For example, electric motors are affected by friction between the rotor and air. Large alternators have significant losses due to windage. To reduce losses, hydrogen gas may be used, since it is less dense.

What is armature loss?

These losses occur in armature and field copper windings. Copper losses consist of Armature copper loss, Field copper loss and loss due to brush contact resistance. Armature copper loss = I_a²R_a (where, I_a = Armature current and R_a= Armature resistance) This loss contributes about 30 to 40% to full load losses.

What is back EMF in motor?

Back EMF is the system in the coil of an electric motor that opposes the current flowing through the coil, when the armature rotates. When the speed varies, the winding characteristics may fluctuate, resulting in variation of back EMF.

What is stator loss?

These losses are also called copper losses. These losses occur due to current flowing in stator and rotor windings. As the load changes, the current flowing in rotor and stator winding also changes and hence these losses also changes. Therefore these losses are called variable losses.

Where is shunt motor used?

shunt motors are used wherever there is a request for stable speed. Shunt DC motors can be used in centrifugal pumps, lifts, weaving and lathe machines, blowers, fans, conveyors, spinning machines, and more.

What is the function of brush in DC generator?

In dc motors, the carbon brush makes sure the commutation process remains free from sparks. This contact is a sliding contact capable of transmitting electric current from static to the rotating part of a generator or electric motor. A single or several carbon blocks composes a brush.

What are the types of DC generator?

DC generators are categorized into three main types based on the methods of field excitation: Permanent Magnet, Separately Excited, and Self-Excited DC generators. The first type excites the field coils by using Permanent magnets, while the separately excited one includes an external force for excitation.

What is the efficiency of DC generator?

DC generators are very reliable with efficiency ratings of 85-95%. They are compact and light in weight. They provide consistent and constant output. They can be used to provide variable output power.

What is iron loss in motor?

Iron losses can be divided into hysteresis losses, eddy current losses and additional losses. Iron losses are given per weight and depend on the frequency and the maximum flux density. This means that the faster the motor rotates, the higher the iron losses.

What is hysteresis loss in dc motor?

Hysteresis Loss in DC Machine

The constant process of magnetic reversal in the armature, consume some amount of energy which is called hysteresis loss. The percentage of loss depends upon the quality and volume of the iron.

What is significance of back EMF?

Significance of Back EMF in DC Motor

When the load on the motor is decreased, then the torque is momentarily more than the requirement so that the armature is accelerated. As the speed of the armature increases, the back emf also increases and causes the armature current is decrease.

What causes hysteresis loss?

Hysteresis loss is caused by the magnetization and demagnetization of the core as current flows in the forward and reverse directions. As the magnetizing force (current) increases, the magnetic flux increases.

What is stray load losses?

The stray load loss can be regarded as the difference of the total iron losses and harmonic rotor cage losses between the no load and load conditions.

What causes windage?

Windage is a force created on an object by friction when there is relative movement between air and the object. There are two causes of windage: the object is moving and being slowed by resistance from the air. a wind is blowing producing a force on the object.

What is iron loss transformer?

Iron loss: This is defined as the loss that is caused due to the alternating flux in the core of the transformer. As the loss occurs in the core, therefore the iron loss is also known as core loss. There are two types of iron losses, and they are eddy current loss and hysteresis loss.

What is hysteresis law?

Hysteresis occurs in a system that involves a magnetic field. Hysteresis is the common property of ferromagnetic substances. Generally, when the magnetization of ferromagnetic materials lags behind the magnetic field this effect can be described as the hysteresis effect.

What are the 3 types of losses in transformer?

What is BH curve?

The B-H curve or magnetisation curve is the graph plotted between magnetic flux density (B) and magnetising force (H). The B-H curve indicates the manner in which the magnetic flux density varies with the change in magnetising force.