Presentation for lesson 1
Оценка 4.6

# Presentation for lesson 1

Оценка 4.6
pptx
07.05.2020
Presentation for lesson 1.pptx

## The theme of the lesson: Electric engine and direct current electrical generator

The theme of the lesson:

Electric engine and direct current electrical generator

## Learning objectives: to investigate the acting model of an electric engine and to explain the received results in a well-argued manner using

Learning objectives:

to investigate the acting model of an electric engine and to explain the received results in a well-argued manner using Faraday's law of induction and Lentz's law.

## W) Express survey 1. The formula for induced

(W) Express survey

1. The formula for induced EMF magnetic field.
2. In which case, the EMF induction will be maximum?
3. In which case, the EMF induction is zero?
4. The cause of EMF induction in a moving conductor
5.What is solenoid?
6.How are the lines of force directed inside and outside the solenoid?
7.The formula of the magnetic induction coil? What does it depend on?
8. What is called alternating current?
9. What is called direct current?

## W) New information: View video:

(W) New information:

View video: Galileo. Experiment. Generator-engine

## Little history: Faraday's experience confirmed the fundamental possibility of building an electric motor

Little history:

Faraday's experience confirmed the fundamental possibility of building an electric motor.
In 1834, B. S. Jacobi created the world's first DC electric motor, which implemented the principle of direct rotation of the movable part of the engine. In 1838, this engine (0.5 kW) was tested on the Neva river to propel a boat with passengers, i.e. received the first practical application.

## The principle of operation of the

The principle of operation of the DC generator

A simple generator is a coil rotating between the poles of a magnet
The Principle of operation is based on the phenomenon of electromagnetic induction

## The principle of operation of the

The principle of operation of the DC generator

When the coil rotates with a certain frequency, its sides cross the magnetic flux Ф and in each conductor is induced e. m. f. E

## The principle of operation of the

The principle of operation of the DC generator

The simplest electric motor is a coil that rotates in a magnetic field.
The action of the engine is based on the Ampere law

## The principle of operation of the

The principle of operation of the DC generator

If you connect the coil to a source of electrical energy, then an electric current will begin to pass through each of its conductors.
This current, interacting with the magnetic field of the poles, creates electromagnetic forces F.

## The principle of operation of the

The principle of operation of the DC generator

When the current direction is selected, a force F directed to the right (according to the rule of the left hand) will act on the conductor located under the South pole, and a force F directed to the left will act on the conductor lying under the North pole.

## Device DC machines 1 – body (frame) 2 – stator (inductor)

Device DC machines

1 – body (frame)
2 – stator (inductor)
On the pronounced poles of the stator (main poles) is the excitation winding, which is a constant current IV
3 – rotor (armature)
4 - armature winding, in which the rotation of the rotor is induced EMF.

## Device DC machines This E. m. f

Device DC machines

This E. m. f. is removed from the armature winding by means of a sliding contact – brushes (5) included between the winding and the external circuit.

## Device DC machines To convert AC to

Device DC machines

To convert AC to DC, a collector is used.

## Device DC machines The principle of its operation is as follows:

Device DC machines

The principle of its operation is as follows:
The ends of the coil are attached to two copper semi-rings (collector plates).
They are strengthened on the shaft of the machine and isolated from each other
On the plates are placed stationary brushes that give electrical energy to the consumer.

## Device DC machines When rotating the coil, the collector plates rotate together with the shaft of the machine so that each brush touches one or…

Device DC machines

When rotating the coil, the collector plates rotate together with the shaft of the machine so that each brush touches one or the other plate.
The brushes on the collector are set so that they are moved from one plate to another at the moment when the EMF in the coil was equal to zero.

## Device DC machines

Device DC machines

## Device DC machines For better use of the armature winding individual turns are connected to each other in series

Device DC machines

For better use of the armature winding individual turns are connected to each other in series.

Each collector plate is connected to the end of the previous and the beginning of the next turn.

## Conclusion: Any DC machine can operate both in generator mode and in motor mode

Conclusion: Any DC machine can operate both in generator mode and in motor mode

## Application Cranes of various heavy industries

Application

Cranes of various heavy industries
Drive, with the requirements of speed adjustment in a wide range and high starting torque
Traction electric drive of locomotives, electric locomotives, motor ships, dump trucks, etc.
Electric starters of cars, tractors, etc. To reduce the nominal supply voltage in car starters, a DC motor with four brushes is used. Due to this, the equivalent complex resistance of the rotor is reduced by almost four times. The stator of such an engine has four poles (two pairs of poles). The starting current in car starters is about 200 amperes. Mode of operation — short-term.

## Advantages: the simplicity of the device and management; practically linear mechanical and adjusting characteristics of the engine; easy to adjust the speed; good starting properties…

the simplicity of the device and management;
practically linear mechanical and adjusting characteristics of the engine;
good starting properties (large starting torque);
more compact than other motors (using strong permanent magnets in the stator);
since the PTA are reversible machines, it is possible to use them both in motor and generator modes.

## Disadvantages: high cost of manufacturing; the need for preventive maintenance of collector-brush units; limited life due to wear of the manifold

high cost of manufacturing;
the need for preventive maintenance of collector-brush units;
limited life due to wear of the manifold.
(The last two shortcomings at the present stage of development of PTA are almost not noticeable).

## Electric motors play a huge role in our modern life, if the electric motor had no light (application as a generator), there would be no…

Electric motors play a huge role in our modern life, if the electric motor had no light (application as a generator), there would be no water at home, since the electric motor is used in the pump, people could not lift heavy loads (use in a variety of cranes) …..

Conclusion: