Phase protection system for protecting a three-phase load

Claim 2

Apparatus for disconnecting a three-phase source of energy from a load in response to the failure of any one phase comprising at least three input terminals adapted to be connected respectively to each phase of said three-phase source of energy, connect means having a control device for connecting the load with said input terminals in response to current flow through said control device, and disabling means responsive to the failure of a signal in any one of said phases for disabling said connect means, whereby said connect means disconnects the threephase source from the load, said disabling means having one main terminal connected to one of said input terminals, another main terminal connected to another of said input terminals, and a control terminal connected to the third input terminal, whereby each phase of the source of energy is individually connected to a different one of said disabling means terminals, said disabling means being operable between a conducting state whereby current flows through said control device, and a nonconducting state to prevent current flow through said control device, said disabling means being rendered nonconducting by the failure of the signal in at least one of said phases.

Claim 3

Apparatus for disconnecting the three-phase source of energy from a load in response to the failure of any one phase comprising at least three input terminals adapted to be connected respectively to each phase of said three-phase source of energy, connect means having a control device for connecting the load with said input terminals in response to current flow through said control device, and disabling means connected to said input terminals and responsive to the failure of a signal in any one of said phases for disabling said connect means, whereby said connect means disconnects the three-phase source from the load, lead means for connecting said control device and said disabling means in a series path between at least two of said input terminals, said disabling means being operable between a conducting state whereby current flows through said control device, and a nonconducting state to prevent flow through said control device, said disabling means being rendered nonconducting by the failure of a signal in at least one of said phases, said disabling means comprising a QuAdrac having first and second anode terminals connected in a series loop with said control device between said two input terminals, and a control terminal connected to said third terminal.

Claim 4

Apparatus for disconnecting the three-phase source of energy from a load in response to the failure of any one phase comprising at least three input terminals adapted to be connected respectively to each phase of said three-phase source of energy, connect means having a control device for connecting the load with said input terminals in response to current flow through said control device, and disabling means connected to said input terminals and responsive to the failure of a signal in any one of said phases for disabling said connect means, whereby said connect means disconnects the three-phase source from the load, lead means for connecting said control device and said disabling means in a series path between at least two of said input terminals, said disabling means being operable between a conducting state whereby current flows through said control device, and a nonconducting state to prevent flow through said control device, said disabling means being rendered nonconducting by the failure of a signal in at least one of said phases, said disabling means comprising a QuAdrac having first and second anode terminals connected in a series loop with said control device between said two input terminals, and a control terminal connected to said third terminal.

Claim 5

Apparatus as in claim 2, and switch means for selectively connecting said control terminal to said third input terminal.

Claim 6

Apparatus as in claim 2, in which said Quadrac includes a pair of silicon controlled rectifiers connected in inverse parallel relationships and having their gate electrodes connected together, said lead means connecting the anode-cathode paths of said silicon controlled rectifiers in said series path and a pair of zener diodes serially connected together in back-to-back relationships with each other and between said control electrodes and the third terminal.

Claim 7

Apparatus as in claim 2 and overload protection means connected to said control terminal, said overload protection means including means responsive to currents above a preselected value for rendering said Quadrac nonconducting.

Claim 8

Apparatus as in claim 4, and first protection second impedances connected between said third terminal and one of said other terminals, said pair of serially connected zener diodes having one end connected to the junction of said first and second impedances, a negative temperature coefficient device connected in shunt with one of said impedances, and heater means connected between at least one of said terminals and the load for increasing the temperature of said negative temperature coefficient device in response to excessive current flow, whereby current is shunted from said gate electrodes to render said silicon controlled rectifiers nonconductive.

Claim 9

Apparatus as in claim 2, and a fourth input terminal adapted to be connected to the neutral main of a three-phase four-wire system, a lead for connecting said fourth terminal to ground, and protection means in said lead blocking DC current flow through said lead.

Claim 10

Apparatus as in claim 7 in which said protection means includes a pair of serially connected electrolytic capacitors having terminals of the same polarization connected together.

Claim 11

Apparatus as in claim 1, and overload means connected to each one of said input terminals and responsive to current flow above a preselected value in any one of said phases for rendering said disabling means nonconducting.