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The stator is the stationary part of a rotary system, found in electric generators, electric motors, sirens, or biological rotors. The main use of a stator is to keep the field aligned.
With the three phase stator winding which delivers the generator current to the rectifier. Both stator and rectifier are stationary. The stator consists of mutually insulated, grooved laminations which are pressed together to form a solid laminated core. The turn of the stator winding are embedded in the grooves.
In motors:
Depending on the configuration of a spinning electromotive device the stator may act as the field magnet, interacting with the armature to create motion, or it may act as the armature, receiving its influence from moving field coils on the rotor
The stator of these devices may be either a permanent magnet or an electromagnet.
The coil can be either iron core or aluminium. To reduce loading losses in motors, manufacturers invariably use copper as the conducting material in windings. Aluminium, because of its lower electrical conductivity, may be an alternate material in fractional horsepower motors, especially when the motors are used for very short durations.
An AC alternator is able to produce power across multiple high-current power generation coils connected in parallel, eliminating the need for the commutator. Placing the field coils on the rotor allows for an inexpensive slip ring mechanism to transfer high-voltage, low power current to the rotating field coil.
Rotor:
The rotor is a moving component of an electromagnetic system in the electric motor, electric generator. Its rotation is due to the interaction between the windings and magnetic fields which produces a torque around the rotor axis.
With a shaft which carries the magnet poles, the excitation winding and, in most alternators, two collector rings. The excitation winding consists of a single circular coil which is enclosed by the claw-pole halves.
Only a comparatively small excitation current is supplied via carbon brushes which are pressed against the collector rings.
Type and construction of rotor:
Generators and alternators have an electromagnetic system consisting of a stator and rotor. The designs for rotor in generators and alternators are “salient pole or cylindrical”.
Salient Pole Rotors
The rotor is a large magnet with poles constructed of steellamination projecting out of the rotor’s core. The poles are supplied by direct current or magnetized by permanent magnets. The armature with a three-phase winding is attached to three slip rings with brushes riding on them and mounted on the shaft. The field winding is wound on the rotor which produces the magnetic field and the armature winding is on the stator where voltage is induced. Direct current (DC), from an external exciter or from a diode bridge mounted on the rotor shaft, produces a magnetic field and energizes the rotating field windings and alternating current energizes the armature windings simultaneously.
Cylindrical Rotors
The cylindrical shaped rotor is made of a solid steel shaft with slots running along the outside length of the cylinder for holding the field windings of the rotor which are laminated copper bars inserted into the slots and is secured by wedges. The slots are insulated from the windings and are held at the end of the rotor by slip rings. An external direct current (DC) source is connected to the concentrically mounted slip rings with brushes running along the rings. The brushes make electrical contact with the rotating sliprings. DC current is also supplied through brushless excitation from a rectifier mounted on the machine shaft that converts alternating current to direct current.
Operating Principle
In a three-phase induction machine, alternating current supplied to the stator windings energizes it to create a rotating magnetic flux. The flux generates a magnetic field in the air gap between the stator and the rotor and induces a voltage which produces current through the rotor bars. The rotor circuit is shorted and current flows in the rotor conductors. The action of the rotating flux and the current produces a force that generates a torque to start the motor. An alternator rotor is made up of a wire coil enveloped around an iron core. The magnetic component of the rotor is made from steel laminations to aid stamping conductor slots to specific shapes and sizes. As currents travel through the wire coil a magnetic field is created
around the core, which is referred to as field current. The field current strength controls the power level of the magnetic field. Direct current (DC) drives the field current in one direction, and is delivered to the wire coil by a set of brushes and slip rings. Like any magnet, the magnetic field produced has a north and a south pole. The normal clockwise direction of the motor that the rotor is powering can be manipulated by using the magnets and magnetic fields installed in the design of the rotor, allowing the motor to run in reverse or counter clockwise.
An alternator pulley is a device that allows a vehicle's alternator to be turned by a belt, which is driven off of the engine's accessory drive system. Commonly made from stamped steel or cast aluminum, an alternator pulley is either grooved for use with a V-type fan belt or designed with multiple grooves to be used with a serpentine-style drive belt, such as the single-drive belt found on late model vehicles. The alternator pulley is sized to avoid over-driving the alternator when the vehicle is operating at highway speeds, while still providing enough speed to produce ample energy to maintain the battery's charge while at idle engine speeds.The purpose of a vehicle's alternator is to provide a charging system for the electronics on the vehicle. The alternator on nearly every type of vehicle in operation is belt-driven. Whether it is a single V-type fan belt used in a system of different fan belts or a single serpentine drive belt, the alternator pulley allows the belt to spin the alternator, thereby providing current to charge the battery. The alternator pulley attaches to the alternator's main shaft with a nut and washer. The typical alternator pulley also doubles as a cooling fan for the alternator, eliminating over-heating of the interior wire, bearings and brushes. Removing the pulley often involves the use of a special alternator pulley removal tool. The pulleys are often an interference or press fit onto the tapered mounting shaft and require a special pulling tool to remove them from the shaft.
Occasionally, a regular gear or pulley puller can be used to remove the pulley, however, this method will nearly always damage the pulley, the alternator or both. The correct tool to remove the pulley can often be borrowed from a local tool or auto parts supply store, and there is seldom a charge for this service.
There is nearly no failure from the pulley and the most typical reason to remove it is to place it on a replacement alternator, as that seldom comes with a pulley installed. The attaching nut can be difficult to remove from the alternator once it is removed from the vehicle. Using an impact gun will occasionally remove the nut, allowing the alternator pulley to be removed. The best method of removing the nut and alternator pulley is to loosen the nut while the alternator is still on the vehicle and prior to loosening the belt. This method uses the belt's tension to hold the pulley while the nut is being loosened.
Rectifier:
A rectifier is an electrical device composed of one or more diodes that converts alternating current (AC) to direct current (DC). A diode is like a one-way valve that allows an electrical current to flow in only one direction. This process is called rectification.
A rectifier can take the shape of several different physical forms such as solid-state diodes, vacuum tube diodes, mercury arc valves, silicon-controlled rectifiers and various other silicon-based semiconductor switches.
Rectifiers are used in various devices, including:
• DC power supplies
• Radio signals or detectors
• A source of power instead of generating current
• As flame rectification to detect the presence of flame
• High-voltage direct current power transmission systems
• Several household appliances use power rectifiers to
• create power, like notebooks or laptops, video game
• systems and televisions.