Direct current measuring system

Claim 2

A current measuring system for use in a direct current electrical system in which the current periodically undulates to zero, comprising: a. means for generating a signal proportional to the rate of change of direct current in a conductor of said electrical system; b. integrating means supplied with an input signal comprising said rate-of-change signal for producing an output signal which is the integral of the input signal, whereby the waveshape of said output signal is substantially a replica of said current; c. means operative in response to said output signal passing a predetermined level while said current is zero to produce a compensating signal dependent on the difference between the value of said output signal and said predetermined level; and d. means for feeding back said compensating signal to the input of said integrating means in a sense that causes said integrating means to restore said output signal to said predetermined level while reducing said compensating signal to zero.

Claim 3

A current measuring system as recited in claim 1 wherein said predetermined level is zero, said output signal has a relatively positive polarity while there is current flowing in said conductor, said compensating signal is produced if the polarity of said output signal becomes negative, and said integrating means rapidly restores said output signal to zero in response to said compensating signal.

Claim 4

A direct current measuring system for use in an N-phase fUll-wave rectifier circuit having N branches which sequentially commence conducting direct current that periodically undulates to zero, comprising: a. N first means respectively adapted to generate signals proportional to the rates of change of current in said branches; b. N second means respectively supplied with the rate signals generated by said first means for producing output signals proportional to the integrals of the associated rate signals, whereby the waveshape of each output signal is a substantial replica of the corresponding branch current; c. N third means for sensing the output signals of the respective second means and for supplying each of the latter means with a compensating signal when its output signal passes a predetermined level; and d. summing means having N inputs and an output, the output signals of all of said second means being respectively applied to said inputs and said summing means being operative to produce at its output a signal proportional to the total current conducted by said N branches of said full-wave rectifier circuit.

Claim 5

A direct current measuring system for use in an N-phase fUll-wave rectifier circuit having N branches which sequentially commence conducting direct current that periodically undulates to zero, comprising: a. N first means respectively adapted to generate signals proportional to the rates of change of current in said branches; b. N second means respectively supplied with the rate signals generated by said first means for producing output signals proportional to the integrals of the associated rate signals, whereby the waveshape of each output signal is a substantial replica of the corresponding branch current; c. N third means for sensing the output signals of the respective second means and for supplying each of the latter means with a compensating signal when its output signal passes a predetermined level; and d. summing means having N inputs and an output, the output signals of all of said second means being respectively applied to said inputs and said summing means being operative to produce at its output a signal proportional to the total current conducted by said N branches of said full-wave rectifier circuit.

Claim 6

A direct measuring system as recited in claim 3 wherein said second means comprise integrating amplifiers.

Claim 7

A direct current measuring system as recited in claim 3 wherein each of said third means comprises a direct current restorer means which ensures that the output signal of the associated second means is at said predetermined level at the start of each current conducting period of the corresponding branch of the rectifier circuit.

Claim 8

A current measuring system for use in a direct current electrical system in which the current periodically undulates to zero, comprising: a. means for generating a signal proportional to the rate of change of direct current in said electrical system; b. an integrating amplifier, including an input to which said signal is applied, an output, and a capacitor connected between said input and said output, said integrating amplifier being designed to produce at its output a signal which is proportional to said current; and c. feedback means connected between said input and said output, said feedback means being operative to sense the signal at said output of said integrating amplifier and to supply said input of said integrating amplifier with a compensating signal when the signal at said output passes a predetermined level due to discharge of said capacitor, said integrating amplifier being operative to rapidly restore the signal at its output to said predetermined level in response to said compensating signal.

Claim 9

A current measuring system for use in a direct current electrical system in which the current periodically undulates to zero, comprising: a. means for generating a signal proportional to the rate of change of direct current in said electrical system; b. an integrating amplifier, including an input to which said signal is applied, an output, and a capacitor connected between said input and said output, said integrating amplifier being designed to produce at its output a signal which is proportional to said current; and c. feedback means connected between said input and said output, said feedback means being operative to sense the signal at said output of said integrating amplifier and to supply said input of said integrating amplifier with a compensating signal when the signal at said output passes a predetermined level due to discharge of said capacitor, said integrating amplifier being operative to rapidly restore the signal at its output to said predetermined level in response to said compensating signal.

Claim 10

A current measuring system as recited in claim 6 wherein the signal at said output of said integrating amplifier is supplied to a metering means.