More recently, the main means of protecting electrical circuits from overload and short circuit were fuses. Technological progress has not passed, and such, at first glance, a simple area, such as disconnecting emergency devices.
The differential automatic machine helps not only when you need to protect the wiring from overheating, it can in some cases save lives. In this case, not only short circuits are dangerous, but also breaks in the conductors, which can freely touch different objects and become the cause of electric shock.
The automatic machine is designed to instantly de-energize the entire electrical circuit or its branch in which a critical situation arose. In order for him to complete this task, a simple processing of information is necessary . The word "differential" in the context of the name of the protective device indicates that it is a comparison of the values of forward and reverse currents in a closed circuit. Opening of contacts occurs when their values cease to coincide.
Industrial enterprises usually use an operating voltage of 380 V, and a three-phase electric machine is installed on the switchboards, responding to emergency-hazardous differences in currents at the input and output of the circuit in each of the phase loads.
To illustrate the operation of this protective device, one can imagine a situation in which an employee inadvertently touched an uninsulated part of a live element. The current hazardous to life is approximately 20 mA. Exposed to it, as a rule, can not let go of the conductor, because of which, after a contact lasting several seconds, it can die.
The differential automatic machine, configured to operate when a current leakage of 10 mA, does not allow the damaging voltage to act on the body for a long time. A person will experience unpleasant sensations, but after the circuit is instantly de-energized, his life will be safe, spasm of the heart muscle will not occur. In this case, in any other case, the machine will pass through its contact groups the current for which it is designed.
The same situation will arise in the event of a break, when the wire touches any grounding element.
Short circuit protection is instantly triggered when the permissible current is exceeded. The wiring safety is also provided in case of a relatively small, but prolonged passage through it of excessive load. Thus, the automatic machine protects the insulation from drying out, and the contact groups prevent premature burnout.
Such protective equipment is used not only in production shops, it is widely used in residential premises (apartments, houses). A single-phase electric machine is increasingly actively displacing plugs, the inconvenience of which is the need to constantly have fusible inserts on hand. It is no secret that a common practice has long been their replacement with "bugs", which often leads to fires. After eliminating the cause of the short circuit, the machine is just enough to turn on.