US3736470A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method and apparatus for detecting phase imbalances
Assignee: Allen Bradley Co LLC
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Filing: 1971-11-15
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Granted: 1973-05-29
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Expires: 1991-11-15
Abstract
Abstract A reference point is established by phase resistors connected to each of three power lines. The referenced voltage established across one of the phase resistors has a 30* phase lag emparted to it and the voltage established across a second phase resistor has a thirty degree phase lead emparted to it. Under normal operating conditions the two phase-displaced voltages cancel when summed by an annunicator circuit, but when an imbalance or phase failure occurs in the power source, cancellation is not obtained and an annunciation signal is generated. A second embodiment emparts a 60* phase lead to a first referenced voltage and a 60* phase lag to a second referenced voltage. The phase-displaced voltages are identical under normal operating conditions, but when an imbalance or phase failure occurs in the power source, a difference is sensed by the annunciator circuit and an annunciation signal is generated.
Inventors
- 👤 D Ford
- 👤 R Waltz
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 19:09
CPC Classifications
H; H02; H02H; H02H3/00; H02H3/26; H02H3/32; H02H3/34; H02H3/353
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
74 words
A method for detecting both phase failures and current imbalances in a polyphase voltage source, the steps comprising: establishing a neutral reference voltage to which all the phases are referred through equal impedances; selecting a pair of referenced voltage phases and imparting a relative preset phase shift to them to render them coincident when the polyphase voltage source is balanced; and combining the selected pair of phase-shifted voltage phases to generate an annunciation signal.
Claim 2
Independent Claim
74 words
A method for detecting both phase failures and current imbalances in a polyphase voltage source, the steps comprising: establishing a neutral reference voltage to which all the phases are referred through equal impedances; selecting a pair of referenced voltage phases and imparting a relative preset phase shift to them to render them coincident when the polyphase voltage source is balanced; and combining the selected pair of phase-shifted voltage phases to generate an annunciation signal.
Claim 3
Dependent Claim
54 words
The method as recited in claim 1 wherein the polyphase voltage source has three phases and the selected pair of referenced voltage phases are shifted sixty degrees with respect to each other such that they are equal in magnitude and 180* out of phase with each other when the polyphase voltage source is balanced.
Claim 4
Dependent Claim
17 words
The method as recited in claim 2 wherein each selected referenced voltage phase is phase shifted 30*.
Claim 5
Dependent Claim
26 words
The method as recited in claim 2 wherein the selected pair of phase-shifted voltage phases are combined by summing them together to generate the annunciator signal.
Claim 6
Dependent Claim
51 words
The method as recited in claim 1 wherein the polyphase voltage source has three phases and the selected pair of referenced voltage phases are shifted 120* with respect to each other such that they are equal in magnitude and in phase with each other when the polyphase voltage source is balanced.
Claim 7
Dependent Claim
17 words
The method as recited in claim 5 wherein each selected referenced voltage phase is phase shifted 60*.
Claim 8
Dependent Claim
28 words
The method as recited in claim 5 wherein the selected pair of phase shifted phases are combined by subtracting them from one another to generate the annunciation signal.
Claim 9
Dependent Claim
111 words
A phase failure and phase reversal detection circuit for a polyphase voltage generated on a plurality of power lines, the combination comprising: a plurality of phase resistors, one connecting each power line to a reference point; phase shift means connected across one of said phase resistors to impart a preset phase shift to the referenced voltage generated across it; and an annunciator circuit connected to receive said phase-shifted voltage from said phase shift means and connected to another of said phase resistors to receive the referenced voltage generated across it, said annunciator circuit being operable to sum said two received voltages and generate an annunciation signal indicative of the Net result.
Claim 10
Dependent Claim
111 words
A phase failure and phase reversal detection circuit for a polyphase voltage generated on a plurality of power lines, the combination comprising: a plurality of phase resistors, one connecting each power line to a reference point; phase shift means connected across one of said phase resistors to impart a preset phase shift to the referenced voltage generated across it; and an annunciator circuit connected to receive said phase-shifted voltage from said phase shift means and connected to another of said phase resistors to receive the referenced voltage generated across it, said annunciator circuit being operable to sum said two received voltages and generate an annunciation signal indicative of the Net result.
Claim 11
Dependent Claim
66 words
A phase failure and phase reversal detection circuit as recited in claim 8 which includes second phase shift means connected to impart a preset phase shift to the referenced voltage generated across the other of said phase resistors and to said annunciator circuit, wherein one of said phase shift means imparts a phase lead and the other imparts a phase lag to the applied referenced voltage.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-05-28 | 1976-11-27 | 1977-05-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-05-28 | 1980-11-27 | 1981-05-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-05-28 | 1984-11-27 | 1985-05-29 | $7700.00 | Window Closed / Lapsed |