The principle of generator voltage regulator

1. Overview

The voltage of the generator will inevitably change with the change of the speed, which contradicts the constant voltage requirement of electrical equipment and battery charging.

Therefore, the generator must have a voltage regulating device so that when the generator speed changes, the generator voltage can be automatically adjusted to keep the voltage constant or within a certain allowable range to prevent the generator voltage from being too high or too low, burning out electrical equipment, overcharging the battery, or undercharging the battery.

The silicon diode of the AC generator has the characteristic of unidirectional conductivity and can prevent reverse current. It determines that the battery cannot discharge to the generator and cause reverse current, so there is no need to set up a reverse current cutoff device. Because the AC generator has the ability to limit the output current to no more than the maximum value, there is no need to use a current limiter, and only a voltage regulator is needed.

2. The basic principle of voltage regulation of voltage regulator

When the generator speed changes, to keep the voltage constant, the only way is to change the magnetic flux of the magnetic pole accordingly, that is, when n increases, the noise is reduced to keep the voltage constant. The magnitude of the magnetic flux noise depends on the magnetic field current, so when the speed changes, the voltage can be kept constant by automatically adjusting the magnetic field current. The voltage regulator regulates the voltage based on this principle.

3. FT61 double contact voltage regulator

1. Structure

The moving contact forms a pair of normally closed low-speed contacts K1 and another pair of normally open high-speed contacts K2 between the two static contacts, which can adjust two-level voltages, so it is called a two-level contact type. The high-speed static contact is directly grounded to the metal base. There are only two terminals for the outside: ignition (or "live wire", "armature", "A", "S", "+") and magnetic field (or "F").

The low-speed contact K1 is connected in parallel with the acceleration resistor (vibration-assisting resistor) R1 and the adjustment resistor (additional resistor) R2; the high-speed contact K2 is connected in parallel with the generator excitation winding; the temperature compensation resistor R3 is connected in series with the magnetizing coil circuit. In addition, there are also the electromagnet core, magnetizing coil, movable contact arm armature, tension spring, etc.

2. Working process

1) When the ignition switch is closed, the engine does not start or runs at a low speed, the generator does not rotate or the speed is very low, the voltage of the regulator live wire terminal to the ground is less than 14V, and the electromagnetic force generated by the current flowing into the magnetizing coil 3 cannot overcome the tension of the spring 4. Therefore, the low-speed contact K1 is still closed.

At this time, the battery provides excitation current to the field winding 8, which is called external excitation.

The separately excited circuit is: positive pole of battery → ammeter A → ignition switch 10 → live wire terminal S of regulator → static contact bracket 1 → low-speed contact S1 → armature 2 → yoke 5 → magnetic field terminal F of regulator → terminal F of generator → brush and slip ring → magnetic field winding 8 → slip ring and brush → “-” terminal of generator → ground → negative pole of battery.

When the generator runs at low speed, the magnetic field current is supplied by the battery, which strengthens the rotor magnetic field and causes the voltage to rise rapidly.

2) The generator speed increases. When the generator voltage is higher than the battery voltage, the field current and the current in the magnetizing coil are both supplied by the generator.

The generator itself provides excitation current to the field winding 8, which is called self-excitation. The self-excitation current is output from the generator A terminal.

3) As the generator speed increases, when the generator voltage reaches the first-level regulation voltage of 14V, the electromagnetic force of the magnetizing coil 3 increases, overcoming the spring tension and sucking the armature 2 down, so that K, opens and is in the middle suspended position.

At this time, the magnetic field circuit is: generator positive pole A→ignition switch 10→regulator live wire terminal S→acceleration resistor R1→adjustment resistor R2→regulator F terminal→generator F terminal→field winding 8→ground.

Since R1 and R2 are connected in series in the magnetic field circuit, the magnetic field current is reduced and the generator voltage is reduced.

When the generator voltage drops to slightly below the operating voltage of 14V, the current passing through the magnetizing coil 3 decreases, the electromagnetic attraction weakens, S1 closes again under the action of the spring, R1 and R2 are short-circuited, the magnetic field current increases, and the generator voltage rises again.

When the generator voltage rises to a level slightly higher than the working voltage of 14V, S1 is opened again and is in a suspended position, and the above process is repeated. The generator voltage decreases again. This is repeated, and S1 vibrates continuously, so that the generator voltage remains at the first-level voltage regulation value of 14V.

4) When the generator is running at high speed, even if S1 is open, the generator voltage will continue to rise due to the small resistance of R1 and R2. At this time, the voltage rises to the secondary voltage regulation value of 14.5V. Since the electromagnetic attraction is much greater than the spring force, S2 is closed. When S2 is closed, both ends of the magnetic field winding are grounded and short-circuited, so the generator voltage drops sharply. At the same time, the attraction of the magnetizing coil decreases, and the armature makes the movable contact in a suspended position. S1 and S2 are both opened, and R1 and R2 are connected in series in the magnetic field circuit, and the voltage rises again. This is repeated, and S2 keeps vibrating on and off, so that the generator voltage is kept at the secondary voltage regulation value of 14.5V for stable operation.

4. FT111 Single Contact Voltage Regulator

FT111 voltage regulator is a single-stage contact voltage regulator with arc extinguishing system produced by Shanghai Industrial Transportation Electric Co., Ltd. It can effectively overcome the disadvantage of common single-stage contact voltage regulator that the contacts are easy to generate sparks and burn quickly. It is suitable for any 12V, 300W~500W internal grounding AC generator. Its structure and circuit are shown in Figure 2-18.

The FT111 voltage regulator is based on the traditional single-stage contact voltage regulator and adds a VD-L, C contact arc extinguishing system consisting of a diode VD, a choke coil L2 and a capacitor C. The arc extinguishing principle can be explained by Figure 2-19.

When the generator voltage reaches the specified value, the magnetizing coil L1 opens the contact, and then the regulating resistor R2 and the accelerating resistor R1 are connected in series to the magnetic field circuit, causing the magnetic field current to decrease sharply. As a result, a high self-induced electromotive force is generated in the magnetic field winding, and the induced current can be

The diode VD and the choke coil L form a loop to play a role of freewheeling and protect the contacts. In addition, a capacitor is connected in parallel at both ends of the contact through L2 to absorb the self-inductance electromotive force and reduce the contact spark.

The advantages of the above-mentioned single-stage contact voltage regulator with arc extinguishing system are: there is only one pair of contacts, which is easy to adjust; it not only reduces the spark of T contact, prolongs the life of the contact but also weakens the radio interference; in addition, when the contact is opened, due to the demagnetization effect of the self-inductance current passing through L2, the closing of the contact is accelerated, thereby increasing the vibration frequency of the contact.

Principle of Automotive Transistor Voltage Regulator

The transistor voltage regulator uses the switching function of the transistor to control the on and off of the generator excitation circuit. When the generator speed changes, the current of the excitation circuit is adjusted to keep the generator voltage stable. This regulator has no contacts and does not require maintenance during use. It has a simple structure, small size, and light weight. It has gradually replaced the contact regulator.

It is composed of 1 to 2 voltage regulator tubes, 1 to 3 diodes, 2 to 3 transistors, several resistors, capacitors and other components. The circuit is connected by a printed circuit board. The shell is made of thin and light aluminum alloy, with a heat sink on the surface and 3 terminals on the outside, namely "+" (or live wire, armature) terminal, "-" (or ground) terminal, and "F" (or magnetic field) terminal, which are connected to the 3 terminals of the generator respectively.

1. JFTl06 transistor voltage regulator

This regulator is a 14V negative pole grounded, and can be used with a 14V, 750W 9-tube AC ​​generator, or a 14V, 6-tube generator with a power less than 1000W. The regulated voltage is 13.8~14.6V. The figure shows the schematic diagram of this regulator:

1. Structure

Resistors R1, R2, and R3 form a voltage divider, R4 and voltage regulator VS2 form a voltage sensitive circuit, transistor VT1 and composite-connected transistors VT2 and VT3 form two switch circuits, and switch control is undertaken by VT1. R4, R5, R6, and R7 are bias resistors of the transistor to ensure the normal operation of the transistor.