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Single Phase Theory

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Magnetism


Permanent magnets-are magnets that do not require any force to maintain their field.

Electron pairs generally spin in opposite directions.

Magnetic materials can be classified into three basic classifications.
Ferromagnetic-easily magnetized. Iron, Nickel, Cobalt. Good material for generators.
Paramagnetic-can be magnetized but not as easy as ferromagnetic. Platinum, titanium, and chromium.
Diamagnetic-no magnetic properties. Copper, Aluminum, brass and antimony. Good for switchgear.
* combining metals you can achieve extremely strong magnetic properties.

Magnetic lines of force are called lines of flux.
-lines of force never close
-form closed loops
-flow from north to south

Strength of the magnetic field
1) Ampere turns
2) core material
The strength of an electromagnet is proportional to it's ampere turns. Ampere turns are determined by multiplying the number of turns of wire by the current flow.

Core material measurement and characteristics
Permeability-is a measure of a material's ability to become magnetized.
Reluctance-is a resistance to magnetism.
Saturation-no more magnetism is possible.
Residual magnetism-magnetism remains
Demagnetism-strike or heat.
Shielding-magnetic field can only be redirected. They cannot be blocked or reflected. It is important that the shield offer a complete path, otherwise they will exit and cause unintended interference.


Electromagnetism

Induction-electromagnetic induction states that whenever a conductor cuts through magnetic lines of flux, a voltage is induced into the conductor. Current flowing through a conductor produces a magnetic field around a conductor.

Left-hand rule for conductors-when the fingers of the left-hand are placed around the windings in the direction of current flow, the thumb points towards the north magnetic pole.

Left-hand generator rule-the thumb indicates thrust or movement of the conductor. The forefinger is flux direction and center finger is current, the direction of the current into the armature.

Three factors that determine the amount of induced voltage are
-the turns of wire
-strength of magnetic field
-the speed of the cutting action
There are 360 degrees total for the most common sign wave.
Peak = RMS x 1.414
RMS = Peak x 0.707
Average = Peak x 0.637 or Average = RMS x 0.9


Inductance Formula Overview

Click here to get the following table in a larger PDF file.