Steuereinrichtung fuer elektrische Belastung

1,201,900. Controlling maximum load. SINGER CO. 20 June, 1969 [18 June, 1968], No. 31227/69. Heading H2H. A switching system for controlling the number of loads energized from a power supply maintains the power drawn from the supply within a predetermined range. The system uses solid-state logic up to the load relays. In the particular system described, a reference voltage representing the maximum permissible load is generated using a Zener diode. The actual power being used is sampled and converted to a first voltage which is scaled to the reference voltage,and a second voltage greater than and bearing a fixed ratio to the first voltage is also generated. These voltages are now compared with the reference voltage in separate comparator circuits comprising unijunction transistors. If the second voltage is less than the reference, pulses are generated to gate thyristors and switch on loads in a predetermined priority order, whilst if the first voltage exceeds the reference, further pulses are sent to a second group of thyristors and loads are switched off in the reverse priority order.