Electric train braking resistance temp. monitoring - using relays controlled by circuit producing quotient of voltage over current

摘要

An arrangement for temp. measurement in electrical braking resistances, in partic. as used in electrical rail systems, uses the variation of the impedance with temp. for determination of average temp. over the whole resistance. The arrangement permits a simple, easily maintained and economical construction. The voltage and current values across and flowing in the braking resistance (1) are sensed by a voltage divider (2) and series shunt (4) respectively, and input to an operational amplifier (6) via d.c. converters (3, 5). The amplifier forms the quotient of voltage divided by current and outputs a temp. dependent voltage to one or more trigger stages (8, 9) with defined threshold levels. The trigger stages operate relays (10, 11) used for indication and control of the temp. to avoid damage due to excess temp.