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Pic. 29. The operation of the generator system.
1. Thermal compensating resistor; 2. Additional resistors; 3. Throttle; 4. Rack with the lower contact of the voltage regulator; 5. Rack with the top contact of the voltage regulator; 6. Voltage regulator winding; 7. Anchor voltage regulator; 8. Voltage regulator cover; 9. Voltage regulator yoke; 10. Voltage regulator base; 11. Rechargeable battery; 12. Generator rectifier; 13. Generator; 14. Generator stator winding; 15. Generator rotor winding; 16. Voltage regulator; 17. Ignition switch; 18. Fuse block; 19. Battery charge control lamp; 20. Relay of a control lamp of a charge of the accumulator battery; I. Voltage regulator RR-380; II. Work at a low frequency of rotation of the generator rotor; III. Work at average and high frequency of rotation of a rotor of the generator.
1. Thermal compensating resistor; 2. Additional resistors; 3. Throttle; 4. Rack with the lower contact of the voltage regulator; 5. Rack with the top contact of the voltage regulator; 6. Voltage regulator winding; 7. Anchor voltage regulator; 8. Voltage regulator cover; 9. Voltage regulator yoke; 10. Voltage regulator base; 11. Rechargeable battery; 12. Generator rectifier; 13. Generator; 14. Generator stator winding; 15. Generator rotor winding; 16. Voltage regulator; 17. Ignition switch; 18. Fuse block; 19. Battery charge control lamp; 20. Relay of a control lamp of a charge of the accumulator battery; I. Voltage regulator RR-380; II. Work at a low frequency of rotation of the generator rotor; III. Work at average and high frequency of rotation of a rotor of the generator.
Voltage regulator
To maintain the voltage in the vehicle's on-board network at a constant level of 1314 V, regardless of the rotor speed, a two-stage vibration voltage regulator of the PP-380 type is used. A non-contact electronic voltage regulator type 121.3702 is installed on some cars. It can be used instead of the PP-380 regulator without any alterations in the car's electrical circuit.
The voltage regulator РР-380 is an electromagnetic relay. Like every relay of this type, it has a magnetic system consisting of a cylindrical core and a U-shaped yoke 9, a coil with a winding 6 on a plastic frame, an armature 7 with a moving contact and two posts 4 and 5 with fixed contacts. Slots in the uprights allow you to move them up and down when adjusting the regulator.
The upper and lower contacts of the armature in combination with the contacts of the racks form two pairs of contacts - the upper and lower. The anchor is pressed by a spring to the contact of the upper rack. By bending the lower bracket of the spring, you can change its tension and thereby adjust the amount of voltage at which the upper pair of contacts will open. Under the base on the insulating pad there are thermal compensating 1 and two additional resistors 2 with a total resistance of 5.5 ohms. Choke 3 serves to reduce sparking between the upper pair of contacts.
Relay of a control lamp of a charge of the storage battery
Relay 20 type RS-702 is designed to turn on the control lamp in the instrument cluster when the generator voltage is not enough to charge the battery. Relay contact opening voltage at (25±5) °C is (5,3±0,4) V, and the short circuit is 0.0-1.5 V. The winding resistance is 29 ohms.
Generator system operation
In the operation of the generator system, three modes can be distinguished: operation at low, medium and high frequency of rotation of the generator rotor.
I mode. This is the mode of starting the engine when it is not yet running or is being rotated by the starter. In this case, consumers are powered by a battery. In this mode, after the ignition is turned on, a current flows in the excitation winding circuit of the generator, closing along the path: "plus" battery - ignition switch 17 - fuse "10" - plug "15", choke core 3, closed top contacts, armature, yoke, plug "67" regulator - plug "67" generator - excitation winding of the generator - "weight" - "minus" battery.
This current creates a magnetic flux, which, when the generator rotor rotates, crosses the turns of the generator stator winding and induces an electromotive force in them. Simultaneously, a current flows through winding 6 of the voltage regulator, which creates a magnetic attraction of the regulator armature to the core, but not yet strong enough to attract the armature to the core and open the upper pair of voltage regulator contacts.
At the same time, the control lamp 19 lights up, signaling that all consumers are powered by the battery. The current through the lamp follows the path: "+" battery - ignition switch - fuse "9" - closed relay contacts 20 - control lamp 19 - "weight" - battery.
II mode. After starting the engine, the rectified voltage of the generator exceeds the voltage of the battery. The excitation winding of the generator and the voltage regulator winding are powered by the generator. In this case, the current flows from the clamp "30" generator and closes through "mass" to the generator rectifier. The battery is being charged.
Under the action of the rectified phase voltage, a current flows through the relay winding 20 along the path: clamp "30" alternator - ignition switch - fuse "9" - relay winding - generator stator winding zero point output plug - generator rectifier. When the rectified phase voltage reaches 5.3-5.7 V, the relay armature is attracted to the core, the relay contacts open, and the lamp goes out, indicating that the rectified generator voltage has become greater than the battery voltage.
With an increase in the frequency of rotation of the generator rotor, the voltage increases and, when it reaches 13.2-14.3 V, the magnetic force overcomes the spring tension, and the armature 7 is attracted to the core. In this case, the upper pair of contacts opens, additional resistors 2 are included in the excitation winding circuit. The generator voltage drops, and the magnetic attraction of the armature to the core decreases accordingly. The spring pulls the armature to its original position, the upper contacts close, the generator voltage rises again, and the described cycle repeats.
Closing and opening of the upper pair of contacts occurs at a frequency of 25-250 times per second, and the generator voltage at the rectifier output rises and falls with the same frequency. Due to the high frequency of opening and closing contacts, voltage fluctuations are imperceptible, and it can be considered almost constant, maintained at a level of 13-14 V.
With a further increase in the frequency of rotation of the generator rotor, the time of the open state of the contacts increases, and the time of the closed state decreases. Due to this, the average voltage at the output of the generator rectifier increases slightly.
III mode. At a high frequency of rotation of the generator rotor, the first stage of regulation (on the top pair of contacts) no longer ensures that the voltage is maintained at the level of 14 V. The generator voltage rises to 13.9-14.5 V, and the armature is attracted to the core until the bottom pair of contacts is closed. In this case, both ends of the excitation winding are closed to "mass".
The current in the excitation winding drops sharply to zero, and the generator voltage also drops sharply. This leads to a decrease in the current strength in the regulator winding and a decrease in the magnetic attraction of the armature to the core. The spring pulls the armature away from the core, the lower contacts open, and the described process is repeated again at a frequency of 80-100 times per second.
Temperature compensation
When the engine is running, the temperature of the regulator rises both from the heating of its winding and resistors, and from an increase in temperature in the engine compartment. Consequently, the resistance of the copper wire of the regulator winding increases, the current flowing through it decreases, and more voltage is required to open the upper contacts and close the lower ones. To ensure that the voltage does not change with temperature fluctuations, it provides two types of temperature compensation.
The first is the inclusion in series with winding 6 of a thermal compensation resistor 1 of 19 ohms from nichrome with a low temperature coefficient of resistance. It reduces the change in resistance in the winding circuit, but does not completely eliminate the voltage increase. Therefore, the regulator also has a second type of temperature compensation - the armature is attached to the yoke using a bimetallic plate. When heated, it tends to bend towards the core and creates a force that counteracts the spring that pulls the armature away from the core.
Voltage regulator operation
The work of the voltage regulator 121.3702 is to turn off the excitation winding if the voltage rises above 13.4-14.6 V, and turn it on if the voltage drops below this limit. This is achieved by turning on and off a powerful transistor in the regulator circuit. Turning off and on the generator voltage fluctuations is almost imperceptible.