Three phase system monitoring and control circuit

Claim 2

A circuit for detecting proper voltage and current sequence of a polyphase electrical system including a polyphase power source and a load comprising: a. means for providing two first signals each indicative of both magnitude and phase displacement of respective voltages of two phases of said source; means to phase shift one of said first signals to provide a displaced first signal; c. means to vectorially add the displaced first signal to the other first signal to provide a voltage sequence signal; d. means for providing two second signals each indicative of both magnitude and phase displacement of respective currents of two phases of said system; e. means to phase shift one of said second signals to provide a displaced second signal; f. means to vectorially add said displaced second signal to the other second signal to provide a current sequence signal; and, g. monitoring means responsive to said voltage sequence signal and said current sequence signal to provide a fault signal when either of said sequence signals is other than of a prescribed value.

Claim 3

The invention in accordance with claim 1 wherein said power source is a three-phase power source.

Claim 4

The invention in accordance with claim 1 further including switching means responsive to said fault signal to disconnect said load from said source.

Claim 5

The invention in accordance with claim 1 wherein the prescribed value of the voltage sequence signal is a minimum acceptable level and the current sequence signal is a maximum acceptable level.

Claim 6

The invention in accordance with claim 4 wherein the minimum acceptable level of the voltage sequence signal is a magnitude in excess of the peak voltage of the polyphase electrical system, and the maximum acceptable magnitude of the current sequence signal is approximately zero.

Claim 7

The invention in accordance with claim 3 wherein said switching means comprises a series connection of a switching device operative to conduct on alternate half cycles of one phase of said system and a current interrupting means in series with said switching device whereby improper operation of said switching device effects the operation of said current interrupting means.

Claim 8

The invention in accordance with claim 6 wherein said current interrupting means is a fuse.

Claim 9

A circuit for detecting proper voltage and current sequence of a polyphase electrical system including a polyphase power source and a load comprising: a. means responsive to the magnitude and phase displacement of two system voltages and two system currents to provide a fault signaL indicative of improper phase sequence; and, b. switching means, responsive to said fault signal, operative to disconnect said source from said load, said switching means including;

Claim 10

A circuit for detecting proper voltage and current sequence of a polyphase electrical system including a polyphase power source and a load comprising: a. means responsive to the magnitude and phase displacement of two system voltages and two system currents to provide a fault signaL indicative of improper phase sequence; and, b. switching means, responsive to said fault signal, operative to disconnect said source from said load, said switching means including;

Claim 11

The invention in accordance with claim 8 wherein said switching device is a thyristor.

Claim 12

The invention in accordance with claim 9 wherein said current interrupting means is a fuse.

Claim 13

A circuit for detecting proper voltage and current sequence of a polyphase electrical system including a polyphase power source and a motor comprising: a. means for providing two first signals each indicative of both magnitude and phase displacement of respective voltages of two phases of said source; b. means to phase shift one of said first signals to provide a displaced first signal; c. means to vectorially add the displaced first signal to the other first signal to provide a voltage sequence signal; d. means for providing two second signals each indicative of both magnitude and phase displacement of respective currents of two phases of said system; e. means to phase shift one of said second signals to provide a displaced second signal; f. means to vectorially add said displaced second signal to the other second signal to provide a current sequence signal; g. an oscillator, responsive to predetermined levels of said sequence signals, to become inoperative; and, h. switching means responsive to the absence of a signal from said oscillator to disconnect said source from said motor.

Claim 14

A circuit for detecting proper voltage and current sequence of a polyphase electrical system including a polyphase power source and a motor comprising: a. means for providing two first signals each indicative of both magnitude and phase displacement of respective voltages of two phases of said source; b. means to phase shift one of said first signals to provide a displaced first signal; c. means to vectorially add the displaced first signal to the other first signal to provide a voltage sequence signal; d. means for providing two second signals each indicative of both magnitude and phase displacement of respective currents of two phases of said system; e. means to phase shift one of said second signals to provide a displaced second signal; f. means to vectorially add said displaced second signal to the other second signal to provide a current sequence signal; g. an oscillator, responsive to predetermined levels of said sequence signals, to become inoperative; and, h. switching means responsive to the absence of a signal from said oscillator to disconnect said source from said motor.

Claim 15

The invention in accordance with claim 11 wherein said switching means includes a series connection of a switching device operative to conduct on alternate half cycles of one phase of said system and a current interrupting means in series with said switching device whereby an improper operation of said switching device effects the operation of said current interrupting means.

Claim 16

The invention in accordance with claim 12 wherein said oscillator is a relaxation oscillator.

Claim 17

The invention in accordance with claim 12 wherein said switching means further includes contact means responsive to the absence of current through said series connection to disconnect said source from said motor.

Claim 18

The invention in accordance with claim 14 wherein said contact means is of the relay type.