Search results
Results From The WOW.Com Content Network
Most [note 1] DC field coils generate a constant, static field. Most three-phase AC field coils are used to generate a rotating field as part of an electric motor. Single-phase AC motors may follow either of these patterns: Small motors are usually universal motors, like the brushed DC motor with a commutator, but run from AC.
An electric generator or electric motor consists of a rotor spinning in a magnetic field. The magnetic field may be produced by permanent magnets or by field coils . In the case of a machine with field coils, a current must flow in the coils to generate ( excite ) the field, otherwise no power is transferred to or from the rotor.
A coil with a core which is a straight bar or other non-loop shape is called an open-core coil. This has lower magnetic field and inductance than a closed core, but is often used to prevent magnetic saturation of the core. A coil without a ferromagnetic core is called an air-core coil. [14]
The three coils are driven with each set 120 degrees in phase from the others. For the purpose of this example, the magnetic field is taken to be the linear function of the coil's current. The result of adding three 120-degree phased sine waves on the axis of the motor is a single rotating vector that always remains constant in magnitude. [17]
The motor–generator set may contain a large flywheel to improve its ride-through; however, consideration must be taken in this application as the motor–generator will lose speed and may draw a large current when power returns or the circuit-breaker is re-closed. If the speed loss is excessive (the power outage is too long), the re-closure ...
In electrical engineering, electric machine is a general term for machines using electromagnetic forces, such as electric motors, electric generators, and others.They are electromechanical energy converters: an electric motor converts electricity to mechanical power while an electric generator converts mechanical power to electricity.
An electric motor or generator consists of a cylinderical rotating part called the rotor and a stationary part called the stator. For maximum efficiency, a gap between the rotor and stator is kept as small as possible, typically 1–2 mm. For most AC generators, the stator acts as the armature, and the rotor acts as the field magnet.
Polyphase coils are electromagnetic coils connected together in a polyphase system such as a generator or motor. In modern systems, the number of phases is usually three or a multiple of three. Each phase carries a sinusoidal alternating current whose phase is delayed relative to one of its neighbours and advanced relative to its other ...