Galvanic isolation

When galvanic isolation (even decoupling) is generally an electrically separating two conductive objects, such as metal plates or circuits, respectively. It may be necessary, for example in metrology applications, and in the data transmission. In the case of circuits, it is therefore not possible to charge carriers to flow from one circuit to another, since there is no electrically conductive connection between the two circuits is composed. However, electrical power or signals can be transmitted via corresponding coupling elements between the circuits. As for isolated compounds electric potentials are separated from each other, one speaks also of potential free connections.

The name " galvanic isolation " or " electrical connection " for the presence or absence of a conductive connection has been coined in connection with the researches of the Italian physician Luigi Galvani.

The technical implementation of

To implement galvanic isolation various components such as transformers, optocouplers or capacitors can be used. The transfer takes place in these cases is through the detour of a magnetic field, respectively, by means of infrared radiation or by charge transfer.

Plastic gears in hand drills or insulating claw couplings are used for insulation protection of electrical hand tools and provide additional isolation between metal drive parts and the outer, exposed metallic parts forth.

Inductive separation

The most common example of galvanic isolation transformers are, especially when they are powered from the mains power source (mains transformers). They provide a galvanic isolation is provided to the network to produce the connected circuits before touching the safety of the network voltage, the voltage adjustment. Which is implemented by two coils electrically isolated from one another, which are located on a common iron core. This construction is also to bear no high voltage on the secondary side when the primary winding is set by a defect under-voltage or blows.

Exchanger is called the inductive electrical isolation, for example, in the audio field, if it is less about the transfer of power, but more to the transmission of analog audio signals with simultaneous separation of the potentials, preferably ground loops to prevent reliable. For example, the microphones in the studio techniques are generally kept floating and connected via transformers to the mixer. Galvanic separation can be realized between mutually rotating parts while avoiding slip rings by means of a rotary transformer.

The transformers that are used in the so-called 100 - volt technology, however serve primarily to impedance matching of the low- sound converter to the output stage or the high-resistance wiring, and the power transmission and does not require inductive isolation. That is, they can choose from a single coil exist with various taps. Also in hi-fi enthusiasts still very popular tube amps require such exchangers to make the amp with standard speakers compatible.

That is, not all transformers are designed or suitable for electrical isolation. Also, variable transformers are single-coil for reasons of cost -saving transformers in the rule and not the separate potentials.

Capacitive isolation

The charge transfer can be used for the galvanic isolation of the signal by high-frequency signals with well-insulated, voltage-resistant small capacitors are capacitively coupled. Potential differences, the voltage changes across the capacitor and compares the differences that way. This form of galvanic separation is not always possible due to the possible failure or penetration of the capacitor due to its limited voltage strength for some applications for reasons of electrical safety.

Information transfer

A galvanically isolated exchange of information is possible through non-electrical transduction pathways with appropriate converters. These include the optical transmission ( optical coupler, light pipe ), the inductive coupling ( transformer and transformer) and the mechanical transmission by compressed air ( pneumatic elements ) or insulating mechanical parts ( for example, relays).

Applications

Galvanic isolation is required in the following cases:

• For safety (eg, medical equipment, electric toys, all mains powered devices with low voltage, such as AC adapters, audio devices, chargers, etc.); see also protective separation.
• Metrological reasons: Isolation of power supply from measuring devices from the electrical circuit of the voltage to be measured or potential separation in Messsignalweg (eg, current clamps, current transformers )
• To prevent ground loops and electromagnetic interference (eg, audio devices, analog and digital signals in the industry, transformer in data networks, eg, Ethernet )

When multiple electrical quantities to be simultaneously measured and recorded, for example, in a computer, the reference potentials are different, then the sensor must be electrically isolated from each other. This can be achieved, for example current transformers, isolation amplifiers or analog-to- optical couplers.

A consistently executed galvanic isolation is an effective protection against electromagnetic interference. This is true even if there is no galvanic connection to other circuits is - long cables can also absorb disturbances without conductive connection and forward in signal inputs. These so-called common-mode noise can be kept away by galvanic isolation of the signal inputs. Industrial facilities and equipment must, for example, so-called burst tests exist, where steep high voltage pulses are capacitively coupled to the cable. The protection against radiated electromagnetic waves is improved by electrically isolating signal inputs. The measures, the term electromagnetic compatibility ( EMC) summarized.

Galvanic isolation is still at the remote data transmission on power lines and to protect against an electromagnetic pulse (EMP ) is required.