GB1384786A - Electrical apparatus including means for automatically matching the apparatus to the internal resistance of a voltage supply - Google Patents

Abstract

1384786 Measuring mains impedance SIEMENS A G 20 April 1972 [24 April 1971] 18471/72 Heading G1U [Also in Division H2] Electrical apparatus such as an x-ray set comprises a resistor 4 connectible as a load across voltage supply terminals 20, a capacitor 9 for producing a control signal which represents a drop in the supply voltage when it is loaded by the resistor, the control signal also representing the internal resistance of the supply, and circuitry 2, 13-16 responsive to the control signal for automatically matching the apparatus to the internal resistance of the supply. The apparatus includes a high voltage generator 1 and an internal resistance matching circuit 2. Initially switches 11, 12, 19 are in their illustrated positions with the resistor 4 loading the supply. When a capacitor 5 is fully charged a time switch 10 changes over the switches 11, 19 to un-load the supply and the capacitor 9 therefore charges to a voltage equal to the difference between the loaded and un-loaded supply voltages, i.e. to a voltage proportional to the internal resistance of the supply. A time switch 17 then changes over the switch 12 to enable the voltage on the capacitor 9 to change the state of one of the Schmitt triggers 13-16 which supplies a signal to the matching circuit 2 to adapt the x-ray set to the internal resistance of the supply. A constant current circuit including a transistor may be connected between diodes 6, 7 to prevent variations in the un-loaded supply voltage affecting the internal resistance measurement.