The differential automatic device is a low-voltage combined electrical apparatus that combines the functions of two protective devices in one case - an RCD and a circuit breaker. Due to this, this product is quite popular and is widely used both in domestic conditions and in production. In this article we will consider the device, purpose and principle of operation of the difavtomat.
Content:
- Appointment
- Device and principle of operation
- Application area
Appointment
Let's briefly consider what a difavtomat is for. Its appearance is shown in the photo:
Firstly, this electrical device serves to protect a section of the electrical network from damage due to the flow of overcurrents through it, which occur when overload or short circuit (circuit breaker function). Secondly, the differential automaton prevents the occurrence of fire and electric shock to people as a result of electricity leaks through damaged cable insulation of a power line or a faulty household appliance (residual current device function).
Device and principle of operation
To begin with, we give the designation in the diagram according to GOST, which clearly shows what the difavtomat consists of:
The designation shows that the main structural elements of the difavtomat are a differential transformer (1), electromagnetic (2) and thermal (3) releases. Below we briefly describe each of the above elements.
The differential transformer has several windings, depending on the number of poles of the device. This element compares the load currents along the conductors, and in the case of their asymmetry, the so-called leakage current appears at the output of the secondary winding of this transformer. It goes to the starting element, which, without time delay, releases the power contacts of the machine.
Also, mention should be made of the button for testing the performance of the protective device "TEST". This button is connected in series with a resistance, which is switched on either by a separate winding on the transformer or in parallel with one of the available ones. When this button is pressed, the resistance creates an artificial imbalance of currents - a differential current occurs and the difavtomat should work, which indicates its good condition.
The electromagnetic release is an electromagnet with a core that acts on the tripping mechanism. This electromagnet is triggered when the load current reaches the operating threshold - this usually happens when short circuit. This release is triggered instantly, in a fraction of a second.
The thermal release protects the electrical network against overload. Structurally, it is a bimetallic plate, which deforms when a load current flows through it, which exceeds the nominal for this device. When a certain position is reached, the bimetallic plate acts on the shutdown mechanism of the difavtomat. The thermal release does not operate immediately, but with a time delay. The response time is directly proportional to the magnitude of the load current flowing through the differential automatic device, and also depends on the ambient temperature.
The operating threshold of the differential transformer is indicated on the case - the leakage current in mA, the rated current of the thermal release (at which it works indefinitely) in A. An example of a marking on the case is C16 A / 30 mA. In this case, the “C” marking in front of the rating value indicates the multiplicity of the electromagnetic release (device class). The letter "C" indicates that the electromagnetic release will trip when the rating of 16A is exceeded 5-10 times.
The video below describes in detail how the difavtomat works and what it consists of:
Application area
What is the differential machine used for, if there are two separate protective devices (RCD and machine), each of which performs its function?
The main advantage of the difavtomat is its compactness. It takes up less space on DIN rail in an electrical switchboard than in the case of two separate units. This feature is especially relevant when it is necessary to install several residual current devices and circuit breakers in the switchboard. In this case, by installing difavtomats, you can significantly save space in the switchboard and, accordingly, reduce its size.
The differential machine is widely used to protect electrical wiring almost everywhere, both in everyday life and in other premises (in various institutions, at enterprises).
Difautomat is in no way inferior to RCDs and circuit breakers similar in characteristics, therefore there are no restrictions in its use. This protective device can be installed both on the input (as a backup) and on outgoing lines. electrical wiring to ensure fire safety, safety of people in relation to electric shock, as well as to protect from overcurrents.
So we examined the device, purpose and principle of operation of the difavtomat. We hope the information provided was useful and interesting for you!
You probably don't know:
- Differential circuit breaker connection diagram
- How to find a short circuit in the network
- What is an RCD in electrical
