Minimum size, integral, A.C. overload current sensing, remote power controller with reset lockout

• US 4,316,230 A
• Filed: 10/09/1979
• Issued: 02/16/1982
• Est. Priority Date: 10/09/1979
• Status: Expired due to Term

• Current Assignee: Eaton Corp. (Wisconsin) (Eaton Corporation PLC.)
• Original Assignee: Eaton Corp. (Wisconsin) (Eaton Corporation PLC.)
• Inventors: Hansen, James E., Rutchik, Walter L.
• Primary Examiner(s): Salce, Patrick R.
• Application Number:
  US06/083,159
• Time in Patent Office: 861 Days
• Field of Search: 361/114, 361/72, 361/115, 361/102, 361/100, 361/98, 361/96, 361/97, 361/59, 361/73, 361/192, 361/191, 361/167, 361/187, 335/13, 335/169, 335/173, 307/115, 307/99
• US Class Current: 361/114
• CPC Class Codes: H02H 3/093 with timing means in general H02H3/027; thermal delay H02H3/085; timing means for undervoltage protection H02H3/247

Abstract

A reset lockout addition to an A.C. overload current sensing, remote power controller of minimum size and weight and integral construction. Current rate sensing wound toroids are used that are small enough to fit around the line terminal studs without having to enlarge prior insulator space available therein. The electronic overload current detecting and tripping control circuit, is replaced by a pair of modules, detector and control modules, having improved performance and a shape and size such that they fit within the relay housing alongside its operating magnet. The detector module has integrator means for converting current rate of change signals into magnitude indicative signals thereby enabling use therewith of rate sensing wound toroids of about one-tenth the size of equivalent current transformer wound toroids. It fully meets the calibrated step function overload trip time requirements while also providing protection for unusual overload conditions such as varying overloads including pulse accumulation effects or repetitive reset, and simulates the response of a thermal element to prevent excess heating of the wire or load that it is protecting under any overload conditions. Moreover, the control module incorporates a single standard CMOS IC logic element that provides a digital solution to the combinations of control conditions requirements while at the same time reducing the number of conventionally-required cutthroat contacts from two to one and isolating the control input from the relay power circuit. Associated with this logic element is a reset lockout circuit responsive to overload trip that prevents resetting of the relay by the set control switch alone but requires an additional manual operation, that is, momentary opening of a reset switch in conjunction with the opening of the set control switch to reset the relay.

Claims

1. In combination with an electrical system supplying a load device from an electrical power supply line having overload current sensing power control means for disconnecting said load device from said power supply line including a latching relay having contacts for controlling connection of said line to said load device and set and trip coils and a cutthroat contact in circuit with said trip coil that closes when said relay is set and reopens when said relay is tripped, means responsive to an overload current on said line for providing an overload trip signal, and control circuit means comprising a set switch and an integrated circuit dual multiplexer having first and second parts including sets of multiplexer inputs associated with first and second multiplexer outputs, respectively, a low enable input, and a pair of common select inputs for controlling said first and second multiplexer outputs, said first part of said dual multiplexer being operable to control setting of said relay in response to the Boolean equation:

space="preserve" listing-type="equation">SET=UNL·

CT·

OLT·

ON

wherein UNL is a combined status "on" signal indicative that the system has not latched into its tripped state and said set switch is "on", and CT is a cutthroat contact open indicative signal at said common select inputs, OLT is an overload trip "off" indicative signal at said low enable input, and ON is a set switch "on" indicative signal at the correspondingly selected input of said first set of multiplexer inputs, and said second part of said dual multiplexer being operable to control tripping of said relay in response to the Boolean equation;

space="preserve" listing-type="equation">TRIP=UNL·

CT·

OLT+UNL·

CT·

ON+UNL·

CT

wherein UNL is said combined status signal and CT is a cutthroat contact closed indicative signal at said common select inputs and OLT is an overload trip "on" signal at the correspondingly selected input of said second set of multiplexer inputs or wherein UNL is a combined status "off" signal indicative that the system has either latched into its tripped state or said set switch is "off" and CT is said cutthroat contact open indicative signal at said common select inputs and ON is said set switch "on" indicative signal;

or wherein said signals UNL and CT are at said common select inputs, the improvement comprising;

reset lockout means incorporated in said control circuit means for preventing resetting of said relay from said set switch following an overload trip comprising;

means responsive to an overload trip signal for introducing a reset lockout signal that alters said combined status "off" signal UNL to a modified combined status "off" signal UNL'"'"' additionally indicative that the system has latched into its reset lockout state, thus inhibiting said set combined status signal UNL at the corresponding select input of said multiplexer and rendering said set switch ineffective to cause resetting of said relay;

a reset switch;

and means responsive to momentary operation of said reset switch for disabling said inhibiting means while said set switch is held open thereby to re-establish the effectiveness of said set switch closure to reset said relay after an overload trip.

2. The combination claimed in claim 1, wherein:

said inhibiting means comprises;

a voltage source;

a gating type thyristor rendered conducting by said overload trip signal and being supplied with anode current from said voltage source through said reset switch whereby said anode remains latched in a "low" state;

and means for applying said "low" state of said anode to inhibit said UNL combined status signal at said multiplexer select input.

3. In an electrical system supplying a load device from an electrical power supply line having overload current sensing power control means for disconnecting said load device from said power supply line including a voltage source and a latching relay having contacts for controlling connection of said line to said load device and set and trip coils supplied from said voltage source and a cutthroat contact in circuit with said trip coil that closes when said relay is set and reopens when said relay is tripped, means responsive to an overload current on said line for providing an overload trip signal, and control circuit means comprising a set switch supplied from said voltage source and an integrated circuit dual multiplexer having first and second parts including sets of multiplexer inputs associated with first and second multiplexer outputs, respectively, and a pair of common select inputs and an enable input for controlling said first multiplexer output, said first part of said dual multiplexer being operable to control setting of said relay in response to an "on" signal ON at a selected input of said first set of multiplexer inputs in the absence of an overload trip signal OLT provided a cutthroat contact open indicative signal CT and a combined status indicative signal UNL are present at said common select inputs, said second part of said dual multiplexer being operable to control tripping of said relay in response to said overload trip signal OLT at a selected input of said second set of multiplexer inputs provided a cutthroat contact closed indicative signal CT and said combined status signal UNL are present at said common select inputs, the improvement comprising:

reset lockout means in said control circuit means for preventing resetting of said relay by operation of said set switch following an overload trip comprising;

a normally-closed reset switch supplied from said voltage source;

a gated current conducting device supplied from said voltage source through said reset switch and responsive to an overload trip signal for inhibiting said combined status signal at one of said common select inputs of said multiplexer thereby to prevent resetting said relay by said set switch alone;

and means responsive to momentary opening of said reset switch while said set switch is held open causing restoration of said current conducting device and termination of said inhibiting thereby to allow resetting of said relay by said set switch.

4. The electrical system claimed in claim 3, wherein:

said gated current conducting device is a silicon controlled rectifier.

5. In an electrical system supplying a load device from an electrical power supply line having overload current sensing power control means for disconnecting said load device from said power supply line including a voltage source and a latching relay having contacts for controlling connection of said line to said load device and set and trip coils supplied from said voltage source and a cutthroat contact in circuit with said trip coil that closes when said relay is set and reopens when said relay is tripped, means responsive to an overload current on said line for providing an overload trip signal, and control circuit means comprising a set switch supplied from said voltage source and an integrated circuit dual multiplexer having first and second parts including sets of multiplexer inputs associated with first and second multiplexer outputs, respectively, and a pair of common select inputs and an enable input for controlling said first multiplexer output, said first part of said dual mutliplexer being operable to control setting of said relay in response to an "on" signal ON at a selected input of said first set of multiplexer inputs in the absence of an overload trip signal OLT provided a cutthroat contact open indicative signal CT and a combined status indicative signal UNL are present at said common select inputs, said second part of said dual multiplexer being operable to control tripping of said relay in response to said overload trip signal OLT at a selected input of said second set of multiplexer inputs provided a cutthroat contact closed indicative signal CT and said combined status signal UNL are present at said common select inputs, and said dual multiplexer being operable to control manual tripping of said relay and resetting thereof in response to operation of said set switch, the improvement comprising:

reset lockout means in said control circuit means for preventing resetting of said relay by operation of said set switch following on overload trip while allowing resetting of said relay by operation of said set switch following manual tripping comprising;

a normally-closed reset switch supplied from said voltage source;

a gated current conducting device supplied from said voltage source through said reset switch and responsive to an overload trip signal for inhibiting said combined status signal at one of said common select inputs of said multiplexer thereby to prevent resetting said relay by closing said set switch;

and means responsive to momentary opening of said reset switch causing restoration of said current conducting device and termination of said inhibiting thereby to allow resetting of said relay by said set switch.

6. The electrical system claimed in claim 5, wherein:

said gated current conducting device is a silicon controlled rectifier.