A generator forces electric charges to move through an external electrical circuit, but it does not create electricity or charge, which is already present in the wire of its w
…indings.enerator forces electric charges to move through an external electrical circuit, but it does not create electricity or charge, which is already present in the wire of its windings. to understand this, you must understand the basic make up of a generator: From a simplistic perspective, there are two main parts of a generator - the stator and the rotor. The stator is the part of the generator that is stationary; the rotor is the part that is spinning. In large generators, the stator and the rotor both have windings of wire on them. The stator windings are typically the output (but not always); the rotor windings are called "field windings". An electric current is applied to the field windings, turning the rotor into a big electromagnet. The rotor is attached to something that causes it to spin - usually a turbine of some type (referred to as the "prime mover"). Since the rotor has become an electromagnet, this spinning magnetic field induces electric current in the stator windings. Now, a permanent magnet can be used instead of field windings, but there is a very good reason to use field windings instead - control. Another component of a generator is the voltage regulator. Its' purpose is to control the voltage to the field windings; As the voltage to the field windings is increased, the strength of the electromagnet will increase. This will cause a larger current to be induced in the stator windings. It is important to understand that when the field winding induces a current in the stator windings, the current in the stator windings "pushes back" on the magnetic field created by the field windings; explanation of why is beyond this (maybe another question if you wish). So, as the field winding voltage is increased, the stator current will push back on the field winding, causing it to slow down. More steam / whatever is being used to spin the prime mover must be increased. A device called the governor is used to keep the generator spinning at the same speed; the governor kicks in, usually openning or closing valves to allow more / less steam to the prime mover, providing more power to the rotor, which in turn keeps the generator spinning at the desired speed. (MORE) 
