Trends in the Development of Voltage Regulation Systems for Tractor Generators
Abstract Generated abstract
This paper reviews the development of automatic voltage regulation systems for tractor and automotive generator installations, with attention to electromagnetic excitation, regulator power requirements, and reliability constraints. It compares contact-vibrating, contact-transistor, transistor, and thyristor regulators, emphasizing the limitations of mechanical contacts and spring-based comparison elements, including wear, corrosion, instability, and the need for readjustment. The authors argue that fully semiconductor regulators offer greater accuracy, stability, and service life, while noting temperature and component-availability limits for transistor designs. Thyristor regulators are presented as a promising direction for generator-integrated systems because controlled diodes tolerate high ambient temperatures and can be driven by low-power transistor amplifiers.
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TRENDS IN THE DEVELOPMENT OF VOLTAGE REGULATION SYSTEMS FOR TRACTOR GENERATORS
G. Ya. Brait, A. N. Korogodsky, G. A. Marchuk, V. A. Pleshkov
(Presented by the scientific seminar of the Departments of Electrical Machines and General Electrical Engineering)
The automatic voltage-regulation system of a tractor generator serves to ensure the nominal operating mode of consumers (with respect to voltage).
Control of an automotive-tractor generator with electromagnetic excitation is carried out by changing the excitation current. The power of the regulating device is determined by the power consumed by the excitation winding (or windings). When an inductor generator with two-sided excitation is used, in a number of cases it is possible to reduce the power and, accordingly, the dimensions of the regulating device by connecting only one of the two excitation windings to the regulator. The second excitation winding is then supplied directly from the rectified voltage. The depth of regulation is achieved by shunting part of the magnetic flux linked with the unregulated winding through the cover–magnetic conductor in which the regulated winding is located [1].
A voltage-regulation system (voltage regulator) is a typical stabilization system. It consists of a measuring device, a comparison element, an error-signal amplifier (not obligatory), and a regulating element.
In automotive-tractor electrical equipment, relay-action voltage regulators are used. The principal types of automotive-tractor voltage regulators are: contact-vibrating, contact-transistor, transistor, and thyristor.
Contact-vibrating voltage regulators have for many years been used with commutator direct-current generators. In these regulators the measuring device, comparison element, and regulating element are combined in an electromagnetic relay with normally closed contacts. The measuring device is the relay coil; the comparison element is a spring connected by a lever with the relay armature and the movable contact; and the actuating or regulating element is a contact pair connected into the excitation-winding circuit. This type of regulator has a number of fundamental disadvantages that call into question the possibility of its use in advanced generator installations. The principal disadvantages are the low reliability of the contact pair, which is subject to wear and corrosion (during its service life the contacts make several million operations under severe thermal conditions), and the low stability of the comparison element—the spring—which requires frequent readjustment during operation.
A contact–transistor voltage regulator is based on the contact-vibration regulator described above, acting on the current of the excitation winding not directly, but through a transistor, whose base current is controlled by the relay contacts. The transistor, whose emitter–collector junction is connected into the excitation circuit, must operate in the switching mode. To avoid overvoltages on the transistor, the excitation winding is shunted by a diode of reverse polarity, serving to discharge the inductance when the transistor is closed.
Reducing the current of the contact pair and eliminating arcing phenomena when the contacts open favorably affect the service life of the latter. At present, the contact–transistor voltage regulator is widely used in automotive and tractor electrical equipment with alternating-current generators (voltage regulator RR362). However, this system retains a significant drawback—low stability and the need for readjustments during operation.
A transistor voltage regulator for automotive and tractor generator installations has already for several years been produced by leading foreign firms. The measuring element in transistor regulators is a voltage divider on active resistances. A proportional part of the regulated voltage is fed to a comparison element, which is a highly stable silicon Zener diode. When the Zener diode breaks down, which occurs when the voltage exceeds the permissible level, the error signal is supplied to the regulating transistor directly or through a transistor current amplifier. A typical circuit of a transistor regulator using \(p\)-\(n\)-\(p\) triodes is shown in Fig. 1. It forms the basis of the transistor voltage regulator being developed at AZTE for tractor generators [2], [3]. The circuit ensures operation of the transistors in the switching mode. The transistor voltage regulator has no moving parts, possesses high accuracy and stability, requires no maintenance during operation, and the service life of the semiconductor elements and, accordingly, of the entire regulator is sufficiently high and meets the requirements imposed on future systems.
Fig. 1
A regulator based on germanium transistors can operate at ambient temperatures up to \(+75^\circ\mathrm{C}\); therefore it must be separated from the generator and located in a place where the temperature does not exceed the specified value, i.e., outside the tractor’s under-hood space.
A regulator based on silicon transistors can operate at temperatures above \(100^\circ\mathrm{C}\) and, in a number of cases, can be built into the generator. Examples of such generator installations using through-flow ventilation are installed on some foreign automobiles (for example, in the USA—the Delcotron generator). Such installations have not become widespread because of the shortage of small, high-power silicon transistors with a large gain coefficient.
More promising regulators intended for installation in the generator are thyristor voltage regulators. In them, the regulating element is a controlled diode connected in series with the field winding in an alternating- or pulsating-voltage circuit (Fig. 2). Controlled diodes are not in short supply and permit high ambient temperatures. The source of power is the generator phase or line voltage. The thyristor is controlled by a low-power transistor amplifier.
Fig. 2
LITERATURE
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S. L. Medovar, A. N. Korogodskii, N. A. Kocherga. Generator with variable rotational speed. Author’s certificate No. 162221. Bulletin No. 9 of 16/IV. 1964.
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N. P. Bogdanets. Device for automatic disconnection of a generator. Decision on the issuance of an author’s certificate of 14/IX. 1968, for application No. 1128649/24-7.
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N. P. Bogdanets, A. N. Shestakov. Voltage regulator for direct- and alternating-current generators. Author’s certificate No. 194916. Bulletin No. 9 of 12/IV. 1967.