US4896242A — Direct AC-DC converter fault protection system

Claim 1

Independent Claim 167 words

In a direct AC to AC converter having: a plurality of bilateral switches (BSW) associated in groups between input lines and output lines of the converter, the BSW's of a group being operatively connected each between a corresponding input line and an output line from such group; and control switching means for controlling said BSW's according to a switching pattern wherein said BSW's are concurrently controlled for conduction in groups pertaining to the different input lines and a corresponding common output line; the combination of: one current sensor operative concurrently in relation to at least the several converter input lines for one group of BSW's whereby a fault current occurring with one BSW will pass to another BSW and said one current sensor will see twice said fault current; and another current sensor operative in relation to the output line from said one group; means being provided for comparing the outputs of said one and another current sensors for detecting a fault current within said one group.

Claim 2

Dependent Claim 167 words

In a direct AC to AC converter having: a plurality of bilateral switches (BSW) associated in groups between input lines and output lines of the converter, the BSW's of a group being operatively connected each between a corresponding input line and an output line from such group; and control switching means for controlling said BSW's according to a switching pattern wherein said BSW's are concurrently controlled for conduction in groups pertaining to the different input lines and a corresponding common output line; the combination of: one current sensor operative concurrently in relation to at least the several converter input lines for one group of BSW's whereby a fault current occurring with one BSW will pass to another BSW and said one current sensor will see twice said fault current; and another current sensor operative in relation to the output line from said one group; means being provided for comparing the outputs of said one and another current sensors for detecting a fault current within said one group.

Claim 3

Dependent Claim 90 words

The converter of claim 1 with said one current sensor being common to all the groups of BSW's; with one said another current sensor being provided for each output line of a group; with means for summing the outputs of said another sensors to derive a current reference signal representative of a normal balance of currents between the various output lines; and comparator means responsive to said current reference signal and to the output of said common current sensor for detecting a critical current in any of said input lines.

Claim 4

Dependent Claim 66 words

The converter of claim 2, with said common current sensor being responsive to all of said converter input lines for one direction of current flow; and with said common current sensor being also responsive to the sum of said group output line currents for the opposite direction of current flow; whereby said common current sensor has a minimal collective response unless there is a fault current.

Claim 5

Dependent Claim 25 words

The converter of claim 2 with means responsive to said comparator means for turning OFF said BSW's in response to such critical current being detected.

Claim 6

Dependent Claim 35 words

The converter of claim 2 with comparator means responsive to the output of said one current sensor and to the output of said another current sensor for detecting a critical current within said one group.

Claim 7

Dependent Claim 27 words

The converter of claim 5 with means responsive to output of said comparator means for turning OFF said BSW's in response to such critical current being detected.

Claim 8

Dependent Claim 63 words

The converter of claim 1 with said one current sensor of a group being responsive to said input lines for one direction of current flow; and with said line current sensor being also responsive to the associated common output line for the opposite direction of current flow; whereby said one current sensor has a minimal collective response unless there is a fault current.

Claim 9

Dependent Claim 148 words

In an AC/AC converter including nine bilateral switches (BSW) associated by groups of three to the three phase lines of the input power supply, each such group being associated to a corresponding one of the lines at the output, the switching pattern thereof being to concurrently control for conduction three BSW's from three different groups and three different output lines; the combination of: three current sensors, each of said current sensors being responsive to the currents flowing within a common group and into a corresponding output line; and means associated with at least one of said three current sensors for detecting a critical current therein; another current sensor being provided for each of said groups and output lines responsive to current flowing therein, said associated means including comparator means responsive to a common group current sensor and to a corresponding another current sensor for detecting such critical current.

Claim 10

Dependent Claim 148 words

In an AC/AC converter including nine bilateral switches (BSW) associated by groups of three to the three phase lines of the input power supply, each such group being associated to a corresponding one of the lines at the output, the switching pattern thereof being to concurrently control for conduction three BSW's from three different groups and three different output lines; the combination of: three current sensors, each of said current sensors being responsive to the currents flowing within a common group and into a corresponding output line; and means associated with at least one of said three current sensors for detecting a critical current therein; another current sensor being provided for each of said groups and output lines responsive to current flowing therein, said associated means including comparator means responsive to a common group current sensor and to a corresponding another current sensor for detecting such critical current.

Claim 11

Dependent Claim 31 words

The converter of claim 8 with means being provided responsive to said critical current level being detected by a corresponding one of said comparator means for turning OFF said bilateral switches.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1993-01-22	1993-07-24	1994-01-23	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1997-01-22	1997-07-24	1998-01-23	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2001-01-22	2001-07-24	2002-01-23	$7700.00	Window Closed / Lapsed

Direct AC-DC converter fault protection system

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