Ground fault detection circuit

Details Ground fault detection circuit Ground fault detection circuit

1997-08-18

2001-02-13

Ponomarenko, Nick (Department: 2834)

Electricity: single generator systems

Automatic control of generator or driving means

Plural conditions

C322S028000

Reexamination Certificate

active

06188203

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates to controllers for generators, such as are used with aircraft engine starters and generators.
It is well known to use generators as starters for motors and engines. For example, in the aerospace industry, DC generators are commonly used as engine starters on small aircraft engines such as gas turbine engines. After the engine is started, the generator typically is used as an electrical power source for the aircraft.
Aircraft manufacturers and governmental regulations have, over the years, gradually increased the demand for more monitoring and control functions to be implemented for these generators, particularly with respect to providing fast and accurate indications of fault conditions to avoid catastrophic generator failures and engine damage. However, space and weight considerations can limit the availability and use of multiple discrete logic circuits. Discrete control circuits also inherently lack central processing control, thus limiting the number of interdependent control functions that can be implemented.
Furthermore, various control and monitoring functions heretofore used with generator discrete controllers can be inadequate or unsuitable for protecting components that can be overstressed or for facilitating acceptable generator operation. For example, linear current limiters for devices subject to current overloads can exhibit large power dissipation, and known switch mode current limiters can deliver excessive currents and therefore not adequately protect interconnect wiring. As another example, it may be desirable in some applications to provide an automatic field flash for the generator without the need for manual pilot control.
The need exists, therefore, for a generator controller that can implement numerous and complex control and monitoring functions to facilitate proper generator operation without a significant increase in cost, space requirements or weight with an increased reliability of generator operation and control.
SUMMARY OF THE INVENTION
In view of the aforementioned needs, the invention contemplates, in one embodiment, a controller for a starter/generator used with an engine, comprising means for monitoring field free wheeling current in a generator field winding; means for monitoring generator voltage and current; and microprocessor control means for controlling generator field current as a function of said monitored generator current, generator voltage and field current.
The invention further contemplates the methods embodied in the operation of such apparatus, as well as a method for detecting field integrity in a generator comprising the steps of:
a. monitoring field free wheeling current in the generator using a rectifier in shunt with the generator field winding; and
b. de-energizing the generator when field free wheeling current is absent during a time period when field free wheeling current should be present.
In another embodiment, the invention contemplates a switching driver overload protection circuit comprising means for controlling current through the device, and a relaxation oscillator for decreasing said current in response to increasing load.
These and other aspects and advantages of the present invention will be readily understood and appreciated by those skilled in the art from the following detailed description of the preferred embodiments with the best mode contemplated for practicing the invention in view of the accompanying drawings.


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