Abstract:
A differential protection system is connected to detect and indicate faults in an exciter by comparing signals developed from the exciter field and from the generator armature. A first signal is developed representing the magnitude of the voltage on the exciter field winding and a second signal is developed representing the vectorial sum of the current and voltage on the armature winding. These signals are compared and a fault indication produced when the magnitude of their difference is at least of a certain value. The differential protection in brushless exciters permits avoiding the use of a fuse in series with each diode of a rotating rectifier.
Abstract:
An overcurrent protective circuit or means comprising static solid state non-linear elements connected in parallel with an input signal conditioning means such that an overload current in a protected circuit is sensed by the input signal conditioning means and then converted into a signal which is applied simultaneously to each of the non-linear elements. An output current which is directly proportional to or varies with the value of overcurrent in the protected circuit is generated by each non-linear element after the overload current exceeds predetermined values which may be different for the respective non-linear elements. The output from each of the non-linear elements, is supplied to a corresponding associated modulating means such as an oscillator, multivibrator or current generator. These modulating means combine to generate a current signal that is proportional to the overload current in the protected circuit raised to some power N where N is related to the number of modulating means. This current is then applied to charge a capacitor which effectively integrates the current with respect to time. Integration converts the charging current into a voltage signal which is directly proportional to the Nth power of the overload current in the protected circuit. The voltage signal is then compared with a reference or threshold voltage in a trigger circuit and when it exceeds the reference voltage, a signal is generated by the trigger circuit which actuates a circuit breaker tripping means causing the circuit breaker protecting the aforementioned circuit to open or trip.
Abstract:
A measuring network in which a ramp generator is energized throughout each alternate half cycle of the frequency to be measured and in which the ramp generator is reset to an initial potential during each of the intervening half cycles whereby the change in potential of the ramp generator is a measure of the half cycle interval and consequently of the frequency when the wave shape remains constant, a measure of changes in wave shape of the cycle when the frequency is constant, and a measure of the frequency regardless of the wave shape when the output quantities of two such networks are summed; one such network measuring the interval of one half cycle and the other measuring the interval of the other half cycle.
Abstract:
Regulated electric power apparatus including a dynamoelectric machine and exciter. A control feedback loop responsive to the parameter to be regulated is modified by a supplementary negative feedback loop responsive to the exciter field current, which forces current into the field and reduces the effective exciter time constant.
Abstract:
The use of a charged capacitor in conjunction with the closing switch associated with a circuit breaker such that when the closing switch is closed, the capacitor discharges through the switch and the primary of a pulse transformer creating a pulse in the secondary of the transformer which, in turn, is used to gate a solid-state control device such as a triac or silicon controlled rectifier. The cathode and anode of the solid-state control device is in electrical series with the closing switch and the spring release coil of the circuit breaker, such that when the previously mentioned pulse is applied it causes the solid-state device to turn on and conduct current through the spring release coil thus actuating the closing of the circuit breaker. In the event the circuit breaker immediately reopens because of a fault in the protected circuit or a similar circumstance, the circuit breaker will not reclose again until the depressed closing switch is opened, thus allowing the aforementioned capacitor to recharge.