초록 ▼

A power controller with overload protection having an alternating current source (AC) connected through power lines (L1, L2) and a pair of power switching devices (FET1, FET2) and a current sensor resistance shunt (SH) in series to a load (LD). A line-derived control power supply circuit (LDS) is co

A power controller with overload protection having an alternating current source (AC) connected through power lines (L1, L2) and a pair of power switching devices (FET1, FET2) and a current sensor resistance shunt (SH) in series to a load (LD). A line-derived control power supply circuit (LDS) is connected through one of the power switching devices (FET1) to the lower line (L1, L2) such that the control power supply current does not flow through the shunt (SH) or the load (LD). Close and open commands are applied from a control switch (CSW) through a threshold detector (DT) and a logic circuit (LG1) to operate a latch (LCH) that turns the power switching devices (FET1, FET2) on and off under the clocking control of a zero voltage detector (ZVD) and a zero current detector (ZCD) and the gating control of a minimum current circuit (MCC). An overload circuit (AVC, ITC, TTC) provides instantaneous trip of the latch on rupture current or timed trip of the latch on smaller overloads. Opto-isolated indicators (SS, ST) indicate trip conditions and loss of line voltage conditions as well as whether the load current is above or below a minimum current value which is a current level adequate for operation of the control system.

대표청구항 ▼

A solid state power controller with overload protection for use in a power circuit having an A.C. power supply source and power line connected to a load, said controller having a pair of series-reverse connected controlled power switching devices and a current sensor connected in series in said powe

A solid state power controller with overload protection for use in a power circuit having an A.C. power supply source and power line connected to a load, said controller having a pair of series-reverse connected controlled power switching devices and a current sensor connected in series in said power circuit, said controlled power switching devices being of a type having two main power terminals and a control terminal for controlling said power switching device by a voltage thereon referenced to a first one of said powcr terminals and having a high forward blocking voltage and a low reverse blocking voltage, and the improvement comprising: a control circuit selectively operable for controlling said power switching devices to energize or deenergize said load; a line-derived rectified control power supply for said control circuit connected to said first power terminal and through the associated one of said controlled power switching devices and through its other power terminal directly across said power supply source so that the rectified control power supply current does not flow through said current sensor or said load thereby to prevent such control power supply current from interfering with the load current sensed by said current sensor as well as to prevent said control power supply current entering as leakage current to the load and so that the control power supply voltage will float with the voltage at said first power terminal thereby to maintain the control terminal to first power terminal voltage high enough to maintain said power switching device conducting despite variation in the voltage at said one power terminal; said control circuit comprising: an overload means responsive to said current sensor detecting an overload condition for rendering said power switching devices non-conducting.