Wattmeter

Patent · Tue Dec 09 04:00:00 EST 1986

OSTI ID:6968662

Kusters, N L; Herriot, G A

This patent describes a wattmeter for determining power corresponding to a.c. voltage and current components from respective proportional representative a.c. signals u and i, comprising (a) first source means for providing a d.c. voltage reference signal U, (b) second source means for providing a d.c. current signal I, (c) first summing means for adding together signals u and U to generate a first output, (d) second summing means for adding together signals i and I to generate a second output, (e) means for multiplying together the first and second outputs to generate a third output, (f) a feedback line supplying the third output to the second summing means, (g) control means acting on the second source means for adjusting the signal I to tend to bring the third output to zero, and (h) display means responsive to the condition of the control means for providing an indication of the power to be determined. The improvement described here is of a means for substantially eliminating from the feedback line an undesirable fundamental frequency a.c. ripple component that is in-phase with the signal u, the eliminating means comprising (i) means for multiplying the third output with the signal u to generate a fourth output, (j) means for integrating the fourth output to obtain a fifth output in the form of a d.c. signal proportional to the undesirable component, (k) means for multiplying the fifth output with the signal u to generate a correction signal equal to and in-phase with the undesirable component, and (l) means for injecting the correction signal with opposite polarity into the feedback line to substantially eliminate the component therefrom.

• Assignee: Canadien Patents and Development, Ltd., Ottawa
• Patent Number(s): US 4628257
• OSTI ID: 6968662
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
420800* -- Engineering-- Electronic Circuits & Devices-- (-1989)
ALTERNATING CURRENT
COMPUTERIZED CONTROL SYSTEMS
CONTROL SYSTEMS
CURRENTS
DESIGN
DIRECT CURRENT
DISPLAY DEVICES
ELECTRIC CURRENTS
ELECTRIC MEASURING INSTRUMENTS
ELECTRICAL EQUIPMENT
EQUIPMENT
FEEDBACK
MEASURING INSTRUMENTS
METERS
OPERATION
POWER METERS
SIGNALS