Short circuit arises at decrease in external resistance of chain to negligible size. That to measure it, find the electromotive force of source of current and its internal resistance then make calculation of short-circuit current.
It is required to you
- tester
Instruction
1. Take source of current and measure its electromotive force (EMF). For this purpose attach the tester which is adjusted for strain measurement to source terminals, being careful. On the screen of tester there will be EMF value of source, measured in volts. Sometimes the EMF of source of current is known in advance, for example, if that is the twelve-volt accumulator, it also is its EMF, and here the internal resistance of source of current most often is unknown.
2. Calculate the internal resistance of source of current. For this purpose, attach to it the consumer, previously having learned its resistance. Use the resistor, with the known size of resistance which is identified by the corresponding code, or measure it by means of tester, having recustomized it for measurement of resistance. Connect it to current source, and measure on it tension by means of tester, having attached it to the resistor in parallel. Tension on the resistor has to be less than the EMF of source. Calculate the internal resistance of source of current. For this purpose from EMF take away tension on the resistor, and divide difference into value of the same tension on the resistor. Result increase by resistor resistance .r= (EDS-U)•R/U. Receive result in Ohms.
3. Calculate short-circuit current. For this purpose EMF value of source of current divide into its internal resistance Ikz = EMF/r. Receive result in amperes. By means of this value it is possible to check short circuit for this specific source of current. If any chain is attached to it, then at achievement of value of current in it the calculated size there will be short circuit and source of current or the element of chain will fail (will fuse). That it has not occurred, install in chain the safety lock which interrupts it at achievement of the value of current intensity equal to short-circuit current. It can be safety or thermal plugs.