Download CURRENT FLOW/ ELECTRON FLOW IN FILM CAPACITORS

CURRENT FLOW/ ELECTRON FLOW IN FILM CAPACITORS
Design 1:
The above figure shows the wound construction of the single side metallized film.
When the supply is applied to the end spray contacts of the capacitor (assuming dc
supply), all the electrons already present in the metallized portion of layer 1 is attracted to
the positive terminal of the supply. So the electron flow is from right to left. Since all the
electrons removed, the layer becomes positively charged.
In layer 2, more number of electrons will get injected from the negative terminal of the
supply. So the electron flow in layer 2 is also right to left. Since all the holes removed/
highly accumulated with electrons, the layer becomes negatively charged.
Note: the current flow direction is just opposite to the electron flow direction.
Design 2:
The above figure shows the wound construction of series metallized film.
Here the layer 3 is called the floating electrode. Though there is no contact with the
supply terminal, it is accumulating charges and electron flow occurs. Since the S2 region
is negatively charged, all the electrons present in layer 3 opposite to S2 will get repelled
and positively charged particles gets accumulated. This is called “ELECTROSTATIC
INDUCTION” and the repelled electrons will gets accumulated in the region opposite to
S1. Thus the electron flow is from right to left in the floating electrode and also in layer
1.
Design 3:
The above figure shows the wound construction of series constructed double side
metallized film
The electron flow is same as like previous construction.
Design 4:
The above figure shows the wound construction of series constructed single side
metallized film and forming three series capacitances.
When the supply is on, more number of electrons is injected in the region S6 of layer 2.
Due to electrostatic induction, electrons in the floating region S3 of layer 1 are moved to
S2. So S2 region of layer 1 is negatively charged. This in turn produces positively
charged in S5 and negatively charged at region S4.
Thus in all layers, electrons flows from right to left or from negative terminal to the
positive terminal.