Electrotechnics: Basics


Wimshurst machine - electrostatic generator

Wimshurst generator is the electrostatic induction machine. It is not a static charge is formed by triboelectricity, when there is friction and by inducing charges. This class of machine efficiencies higher in comparison with those that use friction.

Description of machine Wimshurst

The machine consists of two discs, which are made of a good dielectric, such as rubber, acrylic, etc. These discs are freely impaled on the axis and can be rotated about a horizontal axis. The discs are arranged vertically. With the help of the handle 1 in both drives are counter-rotating. One disc is rotated clockwise and the other counterclockwise. This is achieved by means of drive belts 2 and 3, one of which is twisted through 180° on one of the pulleys. This ensures counter-rotating disks, which is necessary for the induction of charges. Both discs are rotated from one arm and therefore will rotate simultaneously.

On the outer part of each disc 4 are glued metal strips, which do not touch the edges of the disc, and executed at some distance from them. The strips are arranged radially, in the form of rays emanating from the center of the disk. Both discs have the same number and arrangement of the strips can be said that the one disc is a reflection of the other.

Electrostatic induction machine Wimshurst

The strips come in contact with the rotating disks with brushes 5, which serve as a contact for the charge transport through conductors 6, 7, 8 and 9. When the machine Wimshurst metal strips at the contact with the brushes wear out and constructively this wear must be minimized, and contact reliability to the maximum. Conductors 6 and 7 are used for accumulation and removal of charges formed on both disks. The conductors 8 and 9 are arranged each on one side of the disc and connected to diametrically opposed strip.

Electrostatic induction machine Wimshurst. Side view

So we have two types of conductors. One (6 and 7) for the removal of the charges, and 8 and 9 to set the ground - the potential of the neutral line. Conductors 6 and 7 are arranged on the same geometric axis with respect to the diametrical disks and the conductors 8 and 9 are rotated relative to each other at an angle of 90°.

It can also be seen that between the conductors 8 and 9, conductors 6 and 7 are located in the middle, and are spaced at an angle of 45°. Thus we see that the machine is made structurally symmetric and simple enough to make it on their own.

Description of work influence machine

By rotating the handle wheels start to move in opposite directions. Brushes which are usually performed in a tinsel come into contact with the one, followed by the metal strips. With each turn starts to accumulate more and more charge, which provides an increase in capacity at the terminals 6 and 7. For better storage capacitors are used in the form of Leyden jars.

As soon as the accumulated charge reaches the maximum value for your machine design Wimshurst, further increase the charge is terminated. The larger disk diameter and the higher the speed of rotation, the greater the charge is able to develop electrostatic machine.

As the accumulation of charge?

Suppose that the first round is the lack of free charges, which in our case is the lack of free electrons in the metal plate. When driving a second drive plate it will come into contact alternately with brushes on conductor 8, and, accordingly, they will be formed an excess of free charge carriers.

Electrostatic machine - the generator Wimshurst

This is because the plates on both sides, between which a dielectric (material disks) are parallel-plate capacitor, but this capacitor plates which are moving. Electric charge induced on such a capacitor, or in other words - induced.

Then the following occurs. The plates, the second drive, reaching the brushes contact 6 will give the electrons in storage as a Leyden jar (a capacitor). This Leyden jar would accumulate a charge -Q. Then it will be the turn for the next two plates and so on. A similar process occurs on the first disk as it rotates as well, but in another direction. It can be said that free media as it pumped from another Leyden jar, thereby forming on her lack of electrons, and thus it acquires a charge +Q.

If further defuse both contacts accumulated +Q and -Q, either to each other or to transfer charge in the other capacitance, further accumulation of charge becomes again possible.

You can ask. Where does the initial charge? The fact is that it always exists. Any two conductors separated by a dielectric (gas, liquid, solid) always have the capacity, and furthermore, they have a potential difference, which indicates the presence of such a conductor on one more free charge carriers than the other.

Wimshurst electrostatic machine is a machine with a self-excited, i.e. to start its operation does not require supply of any additional charge.

Is Machine Wimshurst energy generator?

More precisely, we can say that the machine is Wimshurst converter mechanical rotational energy into the energy of the electrostatic field. When using such a machine, as indeed any other, there are friction losses, leakage power, etc. Therefore, its efficiency can not be more than 100%, and even it can not be 100%.

As the potential difference than anything more charge will be accumulated, the stronger Coulomb forces will counteract mechanical. In practice this means that with each disk rotation will increase the force applied. In addition there will be losses due to friction in the construction and undesirable leakage of charges.

Date: 01.31.2016

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© Valentin Grigoryev


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