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Home > Mall Dynamic > What Is An Alternator And How Can I Tell IF An Alternator Is Faulty
Alternator is an integral part of engine power system. The alternator continuously charges the battery while the engine is running, ensuring that no power is lost. The alternator can also regulate the power back to the battery so as not to overcharge. Under normal circumstances, we will encounter alternator failure and other conditions, this article introduces what is the alternator at the same time, provide several methods for detecting whether the alternator is faulty
1, rotor: the function of the rotor is to generate a magnetic field. It is mainly composed of two claw poles, magnetic field winding, shaft and slip ring. The two claw poles each have 6 bird-beak magnetic poles, which are pressed on the rotor shaft, and a magnetic yoke is arranged in the cavity of the claw pole, and a magnetic field winding (also known as the excitation winding or rotor coil) is wound around it. The two leads of the magnetic field winding are welded to two slip rings insulated from the shaft, which are used to introduce magnetic field current and contact the two brushes installed on the rear end cover.
2, stator: The stator is composed of a stator core and a stator winding. The function of the stator is to produce alternating current. The stator core is composed of a circular silicon steel sheet with an insulated inner circle and a wire slot. A three-phase symmetrical stator winding is embedded in the slot. The connection of the winding has two ways: star (that is, Y shape) and triangle. Generally, star connection is used, that is, the first end of each phase winding is connected to the silicon diode of the rectifier, and the tail end of each phase winding is connected together to form a neutral point N.
3, brush and brush holder: The brush assembly is composed of two brushes (the role is to introduce magnetic field current), brush spring and brush holder.
4, rectifier: The role is to convert the three-phase alternating current generated by the generator stator winding into direct current, generally composed of 6 silicon rectifier diodes and their cooling plates. The rectifier diode has large working current and high reverse voltage. Alternator rectifier diode has a positive tube and a negative tube, the lead line for the positive diode is called a positive tube, the lead line for the negative diode is called a negative tube.
5, front, back end cover: the front end cover, back end cover is made of non-magnetic material aluminum alloy, less magnetic leakage, and has the advantages of lightweight, good heat dissipation performance. A brush holder and brush are provided on the rear cover.
6, fan and pulley: the front end of the alternator is equipped with a pulley, and the engine drives the generator to rotate through the fan belt. A blade fan is arranged behind the pulley, and an air outlet and an air intake are respectively provided on the front and back end covers. When the engine drives the generator to rotate at high speed, the air can flow through the generator and cool the generator.
The Working Principle OF Alternator
1. The alternator uses the principle of electromagnetic induction to convert the mechanical energy that the engine drives the generator shaft to rotate into electrical energy output. According to Faraday's law of electromagnetic induction, when the magnetic flux (the number of magnetic field lines) across the area surrounded by a closed loop changes (there is relative motion between the conductor and the magnetic field), there is an induced electromotive force in the loop, and if the loop is a closed conductor loop, there is an induced current.
2, the alternator is designed according to the above principles, but the magnetic field of the generator is an electromagnetic field. Give the two brushes a fixed direction of the current (such as brush A flow, brush b flow out), the coil will produce a magnetic field, the direction of the magnetic field with the right hand rule to determine.
3, the three-phase winding of the alternator stator is nested in the stator slot of the generator according to a certain law, and the electrical Angle of each other is 120°. When the rotor field winding is connected to the DC power supply, the claw poles of the rotor are magnetized into the N and S poles. The magnetic field line starts from the N pole, enters the stator core through the small air gap between the rotor and the stator, and finally returns to the S pole through the air gap.
4, synchronous generator is based on the principle of electromagnetic induction, it through the rotor magnetic field and the relative movement of the stator winding, the mechanical energy into electrical energy.
5, when the rotor is driven by an external force, the rotor magnetic field and the stator conductor are in relative motion, that is, the conductor cuts the magnetic force line, so the induced electromotive force is generated in the conductor, and its direction can be determined according to the right hand rule. Because the position of the rotor pole causes the conductor to cut the magnetic line of force in a vertical direction, the induced electromotive force in the stator winding is maximum at this time.
6, when the magnetic pole is turned 90 degrees. The magnetic pole is in a horizontal position, the conductor does not cut the magnetic field line, and its induced electromotive force is zero. The rotor turns 90 degrees again, and the timing stator winding cuts the magnetic force line in the vertical direction, so that the induced electromotive force reaches the maximum, but the direction is opposite to the previous.
7, when the rotor is rotated 90 degrees, the induced electromotive force becomes zero. In this way, the rotor rotates one week, and the induced electromotive force of the stator winding also changes positively and negatively. If the rotor rotates continuously at a constant speed, a periodically changing alternating electromotive force is induced in the stator winding.
The quality of the alternator can be measured by visual inspection methods, such as checking the appearance and clearance of the alternator, checking resistance, checking whether the rotor shaft is bent, and so on. Before disassembly, the initial judgment of the possible fault parts of the starting motor can be targeted to speed up maintenance.
The inspection before disintegration mainly includes the following aspects :① Check the appearance and clearance. Inspect housing and footing for cracks or damage. Swing the pulley around and back to determine whether the axial and radial clearance of the front bearing is larger.
② Check the resistance. Turn the rotor and check the bearing resistance, noise, friction noise and abnormal noise between the rotor and the stator. When the resistance is found to be large, remove the brush and try again to determine whether the resistance is coming from the brush or the bearing.
③ Check whether the rotor shaft is bent. Turn the rotor shaft and visually check the swing difference of the pulley (swing head) to determine whether the rotor shaft is bent. Use DC power supply (6~12V) to excite the generator magnetic field coil; The red and black probes of the voltmeter are also connected between the generator's armature terminal and the ground wire, respectively. If the inspection results meet the above rules, it means that the generator is normal, and the problem is in other circuits. On the contrary, it indicates that the generator itself has a problem and should be disassembled to further identify the cause.
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