Electricity: single generator systems – Automatic control of generator or driving means – Plural conditions
Patent
1988-05-31
1992-03-24
Hickey, R. J.
Electricity: single generator systems
Automatic control of generator or driving means
Plural conditions
322 27, 322 28, 322 73, H02J 714, H02P 930
Patent
active
050991892
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to an alternating current (A.C.) generator to be installed on automobiles and the like.
DESCRIPTION OF THE PRIOR ART
FIG. 1 shows a circuit arrangement of a conventional A.C. generator, in which the reference numeral (1) denotes a three-phase output winding, (2) is a field winding mounted on the rotor of the generator, and (3) is a rectifying circuit for converting an A.C. output of the three-phase output winding (1) into a D.C. (direct current) voltage output, which is used for charging a battery and at the same time, supplied to an electric load. The reference numeral (31) denotes an auxiliary rectifying circuit for outputting of the A.C. output as an exciting current, and (4) is a voltage regulating circuit for regulating the exciting current for the field winding (2) to control the output voltage constant, which is composed of a power tranistor (41) to make and break the exciting current, a driver transistor (42), a zener diode (43) and a voltage detecting circuit (44).
In the A.C. generator thus constructed, when the field winding (2) is supplied with current with the generator rotatably driven, the maximum exciting current will be determined by the resistance value of the field winding (2), which causes the maximum output from the rectifying circuit. When the maximum output is not required, the voltage of the auxiliary rectifying circuit (31) rises to cause the potential of the detecting circuit (44) to increase, which then makes zener diode (43) conductive to turn off the power transistor (41).
With the exciting current for the field winding (2) reduces, the potential of the detecting circuit (44) is reduced to make the zener diode (43) non-conductive, which then causes the power transistor (41) to conduct. The repetition of the above mentioned operation will keep output voltage constant.
The output voltage of a generator of this kind has depended upon the maximum exciting current which is determined by the resistance of the field winding (2) as shown above, and the maximum exciting current varies as this resistance varies to result in changes in the maximum output. Out of these changes is related to the temperature of the field winding (2) to produce a cold output and a hot output. That is, if the charging generator starts running from its cold, shutdown condition when the temperature of the field winding (2) is equal to that of ambient air, an exciting current in response to the resistance of the field winding at that time will flow to produce the maximum output depending on this current. This is what is called the cold output. As the generator keeps running for a period of time, the resistance of the field winding (2) becomes increased by the heat generated in the field winding (2) by the exciting current passing through that resistance. The increase in resistance then causes the exciting current to decrease until heat generated and heat dissipated becomes in balance to produce a constant output. This is what is called the hot output. Generally speaking, it takes several minutes to several tens of minutes for the output to shift from cold to hot. As the torque required to drive the generator is proportional to this output, the design condition should be determined depending upon the cold output when the torque is applied through a pulley and the like which apt to slip against the applied torque and the size of a pulley to be used must be made large in size. FIG. 2 shows output characteristics of a generator of this kind, in which (401) is a cold output characteristic at an ambient temperature of 20.degree. C., (411) is a driving torque characteristic corresponding to this cold output characteristic, (402) is a hot output characteristic at an ambient temperature of 20.degree. C., (412) is a driving torque characteristic under the hot condition, (403) is a cold output characteristic at an ambient temperature of 120.degree. C., and (404) is a hot output characteristic at an ambient temperature of 120.degree. C. The output characteristic (401) is tran
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Iwaki Yoshiyuki
Iwatani Shiro
Kaneyuki Kazutoshi
Hickey R. J.
Mitsubishi Denki & Kabushiki Kaisha
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