Isolation transformer

As an isolating transformer is a power transformer is referred to in the strict sense, which transfers the power supply in the ratio of 1:1 on a secondary winding, which by a so-called protective separation ( electrical Safe isolation ) leading from the mains voltage, related to ground potential primary winding is disconnected. This is achieved by reinforced or double insulation.

Designs

There are single-phase isolation transformers, usually designed in Europe for 230 V, and isolating transformers for three-phase alternating current for the normal European 400 V.

In general, each separate winding transformer is an isolation transformer with a galvanic isolation between the usually space-saving bunk windings, between which there is a sufficient electrical isolation of true, but usually low mechanical strength. This is not considered to be sufficiently safe for personnel protection. In isolating transformers according to standard procedure primary and secondary windings are opposed housed in separate chambers on winding magnetic core.

Applications

For low frequency signals transformers are used to either establish a secure network separation or avoid ground loops and related hum. Here and in communications technology called these transformers transformers.

Power transformers are used to repair and experimental purposes and the operation of Allstromgeräten to reduce the risk of electric shock when working on voltage- operated apparatus or equipment:

It produces a non- connected to the ground output voltage, the potential difference to earth can (usually 4 kV ) have any value up to the insulation resistance without in contact, a current can flow through the body to ground.

Isolating variable transformers are designed as toroidal transformer, and with an adjustable grinder can be any AC output voltage of typically 0 .. 300 V can be removed. Besides serving as an isolating transformer can thus a sub- and over-voltage situation for a module to be tested are given. Compared to a LISN, the curve shape and frequency are not affected.

In medical and ungrounded operation of measuring instruments whose inputs or outputs are based on Gehäuse-/Schutzleiter-Potential, isolation transformers are also used.

Safety

• Isolation transformers do not protect against electric shock when touching both output terminals.
• Isolation transformers do not protect against high voltage above its insulation resistance ( for example, the picture tube anode voltage).

In order to ensure the protection, no electrical connection of the secondary side to ground or the protective conductor must be operationally available. Thus, no current flow, in a single-pole, faulty ground contact, for example, a person who is at ground potential and touches one conductor of the secondary side to emerge. The transformer core can be grounded.

When connecting two devices on the isolation transformer, the housing of the consumer must be kept together on an ungrounded same potential ( ground-free local equipotential bonding ). In repair shops, however, each device must be connected to a separate isolation transformer.