The rated current can pass most long through contacts of a chain, without any consequences for it. At values of current below nominal the maximum power does not develop in chains. When current is higher nominal, the chain can collapse. Short circuit current can be the maximum value of rated current.
It is required to you
- - tester;
- - documentation with the indication of rated voltage and power;
- - current source with known for the EMF and internal resistance.
Instruction
1. Calculate rated current on the rated voltage and resistance of the device or the site of a chain on which it proceeds. Rated voltage is specified in technical documentation. Find resistance in the same place or measure by a tester, having attached it to the device or the site of a chain, previously having switched it to an ohmmeter operating mode.
2. At measurement the site of a chain has to be disconnected from a current source, attach an ohmmeter in parallel. Calculate rated current, having divided rated voltage into the measured resistance of I=U/R. Tension is specified in volts, and resistance in Ohms. Then the rated current will turn out in Amperes.
3. Sometimes the rated power and rated voltage with which the device can work is specified in documents. In this case calculate rated current, having divided value of rated power into the rated voltage of I = P/U. Power has to be specified in watts, and tension - in volts.
4. If rated voltage is unknown, then measure resistance of the device or the site of a chain by means of a tester and divide rated power into this value. From the turned-out number allocate a root square. It will also be rated current of the device.
5. The maximum current possible in a chain is called short circuit current. At achievement of such current, in it there will be a short circuit, and it will fail. It is extreme possible face value for any chain connected to this source of current. For this purpose learn the electromotive force (EMF) and internal resistance of a source of current.
6. Calculate short circuit current, having divided EMF into the internal resistance of Ikz = EMF/r. If during the operation of the device or a chain the current approaches this value, so it is necessary to reduce current source EMF if it is possible, or to increase loading (general resistance) of a chain.