Power monitor system

In apparatus to monitor electrical three-phase power, the combination comprising

• (a) a three-phase voltage averaging detector to continuously monitor three-phase voltage, and to generate a DC voltage output (V.sub.10) that is directly proportional to the average phase voltage, independent of phase sequence, and that is also inversely proportional to unbalance between any two phases,
• (b) a high voltage comparator circuit operatively connected with the V.sub.10 output of the three-phase voltage averaging detector to compare said signal V.sub.10 with a reference signal V.sub.15, thereby to produce an output signal V.sub.40,
• (c) and a low voltage comparator circuit operatively connected with output V.sub.10 of the three-phase voltage averaging detector and also with a reference signal V.sub.16, thereby to produce an output V.sub.50,
• (d) and a fault signal activator circuit coupled to V.sub.40 and V.sub.50 to produce a fault signal in the event either of V.sub.40 and V.sub.50 reaches a corresponding limit,
• (e) a three-phase voltage and phase sequence detector to continuously monitor the three-phase voltage and to generate a floating reference voltage V.sub.20 that is proportional to the average three-phase voltage, that is also proportional to the unbalance between any two phases, and that is high for reverse rotation,
• (f) a phase unbalance and reverse phase sequence comparator circuit operatively connected to receive said V.sub.10 and V.sub.20 outputs, and to produce an output V.sub.30 fed to the input of the fault signal activator circuit, whereby a predetermined low value of V.sub.30 will cause production of a fault signal,
• (g) said three-phase voltage and phase sequence detector comprising an RC and diode network including R.sub.10 and D.sub.16 in series in a first phase branch, R.sub.11 and D.sub.18 in series in another phase branch, R.sub.12 and D.sub.20 in series in a further phase branch, C.sub.1 connected between R.sub.10 and another phase branch, C.sub.2 between R.sub.11 and said further phase branch, and C.sub.3 connected between R.sub.12 and said first phase branch, one terminal for V.sub.20 connected with each of said diodes D.sub.16, D.sub.18, and D.sub.20.

In apparatus to monitor electrical three-phase power, the combination comprising

• (a) a three-phase voltage averaging detector to continuously monitor three-phase voltage, and to generate a DC voltage output (V.sub.10) that is directly proportional to the average phase voltage, independent of phase sequence, and that is also inversely proportional to unbalance between any two phases,
• (b) a high voltage comparator circuit operatively connected with the V.sub.10 output of the three-phase voltage averaging detector to compare said signal V.sub.10 with a reference signal V.sub.15, thereby to produce an output signal V.sub.40,
• (c) and a low voltage comparator circuit operatively connected with output V.sub.10 of the three-phase voltage averaging detector and also with a reference signal V.sub.16 thereby to produce an output V.sub.50,
• (d) and a fault signal activator circuit coupled to V.sub.40 and V.sub.50 to produce a fault signal in the event either of V.sub.40 and V.sub.50 reaches a corresponding limit,
• (e) a three-phase voltage and phase sequence detector to continuously monitor the three-phase voltage and to generate a floating reference voltage V.sub.20 that is proportional to the average three-phase voltage, that is also proportional to the unbalance between any two phases, and that is high for reverse rotation,
• (f) and including a phase unbalance and reverse phase sequence comparator circuit operatively connected to receive said V.sub.10 and V.sub.20 outputs, and produce an output V.sub.30 fed to the input of the fault signal activator circuit, whereby a predetermined low value of V.sub.30 will cause production of a fault signal.

A single compact plug-in monitoring device connected with a three-phase electric circuit and having phase angle and voltage detection circuitry and comparator circuitry connected therewith to detect

• (a) overvoltage
• (b) undervoltage
• (c) phase unbalance
• (d) phase reverse rotation
• (e) return a power after interruption, said comparator circuitry including a phase unbalance and reverse rotation comparator having three balanced RC circuits, and there being means operatively connected to said comparator circuitry to provide a fault signal during the first seconds of operations, for dropping out a circuitbreaker on return of line power after power interruption,
• (f) said comparator circuitry including two additional comparators having operational amplifiers to compare a DC signal (proportional to the average three-phase voltage) with two fixed reference signals (representing high and low voltage limits) and one floating reference signal (representing phase unbalance and reverse rotation).