29-01-2013, 02:51 PM
Motor Fundamentals
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INTRODUCTION
Before we can examine the function of a drive, we must understand the basic operation of the motor. It is used to
convert the electrical energy, supplied by the controller, to mechanical energy to move the load. There are really two
types of motors, AC and DC. The basic principles are alike for both. Magnetism is the basis for all electric motor
operation. It produces the force required to run the motor. There are two types of magnets the permanent magnet and
the electro magnet. Electro magnets have the advantage over permanent magnet in that the magnetic field can be made
stronger. Also the polarity of the electro magnet can easily be reversed. The construction of an electro magnet is simple.
When a current passes through a coil of wire, a magnetic field is produced.
DC Motor
When a current passes through a conductor, lines of magnetic force (flux) are generated around the conductor. The
direction of the flux is dependent on the direction of the current flow. If you are thinking in terms of conventional current
flow (positive to negative) then, using your right hand point your thumb in the direction of the current flow and your
fingers will wrap around the conductor in the same direction of the flux lines.
AC Motor
The AC motor operates on the same principle of the OC motor (interaction between magnetic lines of flux). One major
difference is the OC motor requires DC current and the AC motor requires AC current. There are basically two types of
AC motors: synchronous and induction. The basic principle for synchronous motors can be shown using two electro
magnets and a permanent magnet.