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Explanations

General

Terminology

Rated output: The rated output is the power at the output of the transformer. It is the product of the rated output voltage and the rated outout current.

Rated supply voltage: The supply voltage assigned to the transformer by the manufacturer for the specified operating condition of the transformer.

Rated output voltage: The output voltage at rated supply voltage, rated frequency,  rated output current and rated power factor.

No-load output voltage: The  output  voltage when the  transformer is connected to rated supply voltage at rated frequency with no-load on the output.

No-load current: The  input  current  when the transformer is connected to rated supply voltage at rated frequency with no-load on the output.

No-load input: The input of the transformer when connected to rated supply voltage at rated frequency with no no-load on the output.

Short-circuit voltage: The voltage to be applied to the input winding, to produce in the short-circuit output winding a current equal to the rated output current. The short-circuit voltage is usually expressed as a percentage of the rated supply voltage.

Insulation class

The insulation materials are according to IEC 85 and IEC 216:

Thermical resistance of insulating material. Insulation classes:

A (105°C), E (120°C), B (130°C) or F (150°C) The transformers have insulation class E, if no specification is in order.

The windings have a resin-impregnation and are oven-dried. This impregnation is a protection against humidity due and the winding has a mechanical stability. High-grade copper wires prepare a high insolation. Dynamo sheets and grain orientated electro-sheets are used for the transformer cores. This guarantees a high efficiency.

Short-circuit protection

Transformers are classified according to short-circuit protection or against abnormal use.

Short-circuit proof transformer
A transformer in  which the temperature does not exceed the specified limits when the transformer is overloaded or short-circuit and which continues to meet all requirements of this standard after the removal of the overload or short-circuit.

Non-inherently short-circuit proof transformer
A short-circuit proof transformer equipped with a protective device, which opens the input circuit or the output circuit, or reduces the current in the input circuit or the output circuit, when the transformer is  overloaded or short-circuit and which continues to meet all requirements of this standard after the removal of the overload or short-circuit and resetting of the protective device.
Examples of protective devices are fuses, overload releases, thermal fuses, thermal links, thermal cut-outs and ptc resistors.

Non-short-circuit proof transformer
A transformer which is intended to be protected against excessive temperature by means of a protective device not provided with the transformer and which continues to meet all the requirements of this standard after the removal of the overload or short-circuit and resetting of the protective device.

Fail-safe transformer
A transformer which after abnormal use, fails to function by an interruption of the input circuit but presents no danger to the user or surroundings.

ELV (Extra- ow oltage)
A voltage not exceeding the upper limit of band 1

SELV
A voltage which does not exceed 50 V a.c. or 120 V ripple free d.c. between any conductor and earth, in a circuit, which is isolated from the supply mains by means such as a safety isolating transformer.

PELV – circuit
An  ELV  circuit with protective separation from other circuitsand which, for functional reasons, may be earthed and/or the exposed-conductive-parts of which may be earthed.

FELV – circuit
An ELV circuit having the ELV voltage for func- tional reasons and not fulfilling the requirements for SELV or PELV.

SELV, PELV, FELV

S = Safety
P = Protective
F = Functional
ELV = Extra Low Voltage

Standards

Quality

Transformers, reactors and power supply units have been produced in accordance with national and international regulations.

Transformers and reactors
DIN VDE 0532 / 0570 DIN EN 61558

Small power transformers, control transformers
DIN VDE 0570 DIN EN 61558 IEC 14 D

Isolating and safety isolating transformers
DIN VDE 0570 DIN EN 61558 DIN EN 60742

Toroidal variable transformers
DIN VDE 0552 / 0570

Isolating transformers for the supply of medical rooms
DIN VDE 0570 / 0107 DIN EN 60742

The lifetime of transformers and reactors is outstanding, because the quality of materials and the producing is high-grade.

All ELTRA products are submitted to a 100% piece final test.

Protection class

Transformers are classified according to their protection against electric shock.

Calss I transformer
is a transformer in which protection against electric shock does not rely on basic insulation only, but which includes an additional safety precaution such as an earthing terminal.

Class II transformer is a transformer in which protection against electric shock does not rely on basic insulation only, but in which additional safety precautions such as double insulation or reinforced insulation are provided, there being no provision for protective earthing or reliance upon installation conditions.

Class III transformer is a transformer in which protection against electric shock relies on supply at SELV and in which voltages higher than those of SELV are not generated.

CE labeling

In order to fulfil the applicable EU guidelines, all ELTRA products are provided with a CE sign. In order however to achieve conformity with the EU low voltage directive 2014/35/EU, a cover must be provided for some transformers, reactors and power supply units by the installer of the system, since no advance protection against direct contact is possible here for design reasons.