Electricity: single generator systems – Automatic control of generator or driving means – Voltage of generator or circuit supplied
Patent
1979-12-04
1982-07-20
Hickey, Robert J.
Electricity: single generator systems
Automatic control of generator or driving means
Voltage of generator or circuit supplied
322 58, 322 73, H02J 714
Patent
active
043408494
DESCRIPTION:
BRIEF SUMMARY
STATE OF THE ART
The invention relates to a circuit for smoothing a generator voltage especially an AC generator for the on-board electrical supply in motor vehicles, ships and the like. Electric generators are known for providing the on-board electric supply of a motor vehicle. In recent times, so-called AC generators have found increasing application and the generated electrical voltage is rectified prior to connection to the vehicles electrical system; this system is a DC voltage system principally because a storage battery is used for storing the electrical energy.
A customary AC generator may be constructed, for example, to include a rotor which induces a voltage within a three-phase stator coil which is a stationary part of the generator and which may be connected in a star or triangle configuration. The induced voltage is then rectified by means of a rectifier bridge circuit having three so-called positive diodes and three so-called negative diodes. The rotor carries an exciter winding which may be a normal ring coil which receives the necessary exciter current from a regulator. The exciter winding may be associated with magnetic poles, for example two claw-pole halves, which interleave and surround the exciter winding on both sides. The exciter current is applied to the exciter coil by means of carbon brushes which bear against two slip rings mounted on the rotor shaft. It is customary to take off the exciter current over diodes separate, called exciter diodes, from the individual phase windings of the stator winding and to apply them to the exciter windings via a regulator which has at least one main control path. The construction of the regulator is such that it regulates the generator voltage independently of the load and speed of rotation to a constant value by regulating the exciter current for the exciter windings in the desired manner. Inasmuch as each separate phase of the stator winding generates a substantially sinusoidal alternating voltage, the rectified generator voltage is composed of a DC component and, superimposed thereupon a ripple AC component. The degree of ripple depends on the number of rectified half-waves per unit time and this number of half-waves in turn depends on the frequency of alternations of the magnetic field. The regulator can perform its task of maintaining a constant value of the generator voltage in a satisfactory manner only if the generator voltage is as smooth as possible, i.e., if the regulator receives an input voltage which, while proportional to the exciter voltage generated by the generator, exhibits as little ripple as possible.
In this connection, it is known to associate a capacitor with the regulator input in the manner of a filter capacitor which serves to smooth the regulator input voltage and thus also to smooth the final generator output voltage because such a capacitor receives charge when the voltage is excessive (voltage peak) and returns charge when the voltage decreases again. However, it is a particular disadvantage of a smoothing process which depends on a capacitor that the ripple of the voltage is only reduced but cannot be fully removed. Furthermore, the relatively high currents and low voltages which are predominant in motor vehicles or similar systems using AC generators require a capacitor with a relatively very high capacitance to obtain sufficient smoothing.
THE INVENTION
Briefly, a transistor, receiving input signals through a small capacitor, is connected to modify the voltage applied to the regulator reference circuit, the transistor operating as an inverter to apply a 180.degree. out-of-phase ripple voltage thereto, to thereby compensate for ripple in the generator, so that the reference circuit of the voltage regulator will be essentially free from ripple and thereby permit output of the voltage regulator, controlling the field or exciter winding of the generator, likewise to be independent of ripple of the output voltage provided by the generator.
The circuit has the advantage that the ripple of the voltage generated by t
REFERENCES:
patent: 3942097 (1976-03-01), Itoh et al.
patent: 4129819 (1978-12-01), Arendt
patent: 4141613 (1979-02-01), Mori et al.
patent: 4143313 (1979-03-01), Arendt
patent: 4223363 (1980-09-01), Santis et al.
patent: 4237412 (1980-12-01), Rundlof
Hickey Robert J.
Robert & Bosch GmbH
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