Technical Data and Definitions


Today the wear life span of transformers and reactors is nearly unlimited in consequence to theuse of upgraded materials and highly qualified manufacturing. The Roller & Fischer inc. overallis structured according to the DIN EN ISO 9000 quality management system and is certifiedby the M-Zert according to DIN ISO 90001:2000. The QM systems include the examination ofall Q-elements from order input to the delivery of the devices. All Roller & Fischer products aresubjected to a 100% quality inspection.


The insulation materials are in accordance with the IEC 85 and IEC 216:Thermal resistance of insulating material. Thermal classes: A (105°C), E (120°C), B (130°C), or F (155°C) The transformers are fabricated according to the insulation class E, if no other class is specified. The electricalcoils are resin-impregnated and oven dried. This impregnation provides mechanical stability, protection against humidity and the highest insulation resistance. Principally we use enamelledcopper wires for high grade isolation. Dynamo sheets and grain orientated electro-sheets areused for the transformer cores. This guarantes a high efficiency.


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

Transformers and reactors
DIN EN 61558 IEC 14 / 7 (DIN VDE 0532 / 0570)

Small power transformers, control transformers
DIN EN61558 IEC 14 D (DIN VDE 0550 / 0570)

Isolating and safety isolating transformers
DIN EN 60742 DIN EN 61558 IEC 742 (DIN VDE 0551 / 0570)

Toroidal variable transformers
DIN VDE 0552

Isolating transformers for the supply of medical rooms
DIN EN 61558 (DIN VDE 0551 / 0570 / 0107)

Protection Classes

Transformers are separated into three protection classes against dangerous shock current.

Class I transformers are transformers in which protection against electric shock does not relyon basic insulation only, but which include an additional safety precaution such as an earthingterminal.

Class II transformers are transformers in which protection against electric shock does not relyon basic insulation only, but in which additional safety precautions such as double insulation orreinforced insulation are provided, there being no provision for protective earthing or relianceupon installation conditions.

Class III transformers are tranformers in which protection aginst electrik shock relies on the SELV supply where no higher voltages is generated as the SELV supply.

CE Labelling

In order to fulfil the applicable EU guidelines, all Roller & Fischer products are provided with a CE label. However to achieve conformity with the EU low voltage directive 73/23 EEC,the raiser of the electrical installation must provide an additional coverage, because construction-conditioned there is no protection possible against direct contact.


Rated output is the rated supply voltage power at the output of the transformer. It is the productof the rated output voltage and the rated output current.

Rated supply voltage is the dedicated supply voltage of a transformer to keep the defined operating conditions.

Rated output voltage is the output voltage at rated supply voltage, rated frequency, rated output current an rated power factor.

No-load current is the output current of an unstressed transformer connected to the rated supply voltage at rated frequency.

No-load power is the power unstressed of the transformer connected to a rated frequency with no-load at the output.

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

Short Circuit Protection

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

Short-circuit proof transformer is a transformer in which the temperature does not exceed the specified limits if the transformers is overloaded or short-circuited an which continuesto meet all requirements of this standard after the removal of the overload or short-circuit.

Non-inherently short-circuit proof transformer is a transformer equipped with a protective device, to open 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-circuited. The transformer continues to meet all requirements of this standard after the removal of the overload orshort-circuit and after resetting the protective device. Examples of protective devices are fuses, overload releases, thermal fuses, thermal links, thermal cut-outs an ptc resistors.

Non-short-circuit proof transformer is a transformer which is intended to be protected against excessive temperature by a protection equipment, which is not part of the transformer.

Fail-safe transformer is a transformer fails due to abnormal use but presents no danger tousers or surroundings.

ELV Extra-low-voltage is a voltage not exceeding the upper limit of voltage range 1.

SELV is 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 silating transformer.

SELV-circuit is an ELV circuit with separation protective from other circuits. Also it does not have connections to earthing and other tangible conductive parts.

PELV-circuit is an ELV circuit with protective separation from other circuits and which, for functional reasons, may be earthes and/or the exposed-conductive-parts of wich may be earthed.

FELV-circuit is an ELV circuit having the ELV voltage for functional reasons and not fulfilling there quirements for SELV or PELV.The letters of the acronyms SELV, PELV and FELV relate to the following key:

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


Control transformer
DIN VDE 0550 / 0570 / 0113 DIN EN 60742 DIN EN 61558
The control transformer with electrical separated winding acts as supply for auxiliary power circuits,according to DIN VDE 0570, part 2-2. With inductive load it has a low voltage drop. Accordingto DIN VDE 0113, part 1, a control transformer is required in electrical systems including more than 5 electro-magnetic, actuation coils, relays or sim, or control and signal devices are fitted outside the control cabinets and machines and when electronic control or signal circuits areto be supplied. Scope: supply voltage <1000 V, rated frequency <500 Hz

Isolating transformer
DIN VDE 0551 / 0570 DIN EN 60742 DIN EN 61558
The isolating transfomer is a transformer with protective separation between the input and outputwinding. Isolating transformers are used for electrical separation of power circuits, in orderto limit dangers, which can result from unintentional simultaneous contact of the erarth andparts under voltage or metal parts, which could be under voltage, when there is a fault in theinsulation system. The protective measure “protective insulation” can be fulfilled by isolatingtransformers. VDE 0551 part 1, VDE 0570 part 2-4 all apply for isolating transformers. Scope:supply voltage < 1000 V, output voltage < 1000 V (load and no load), frequency < 500 Hz,output for single phase < 25 KVA and output for three phase < 40KVA.

Safety isolating transformers
DIN VDE 0551 / 0570 DIN EN 61558
A safety isolating transformers is an isolating transformer for supplying SELV-or PELV-circuits,Safety transformers are designed to supply a device or distributor power circuit in order to prevent impermissibly high or possibly dangerous contact voltage. The protecive measure “lowsafety voltage” can be fulfilled by safety isolating transformers. DIN VDE 0551 part 1, DIN VDE0570 part 2-6 all apply for safety transformers. Scope: supply voltage < 1000 V, frequency <500 Hz, output voltage < 50 V a.c., or < 120 V ripple free dc, output for single phase y 10 KVA, output for three phase < 16 KVA.

Isolating transformer for the supply of medical rooms
DIN VDE 0551 / 0570 / 0107 DIN EN 60742 DIN EN 61558
An isolating transformer for use in medical room applications has double or reinforced insulationbetween each part of the transformer except between the core and the body and screening between two windings. Single phase transformers have a mid-point for monitoring equipment of the secondary winding The lead out of the midpoint shall be connected to a separte terminal. The transformersare used in electical installations in hospitals and locations for medical usw autside hospitalin IT systems. The provisions of DIN VDE 0107 /11.89 apply. Requirements: Short circuit voltage max 3% of the rated input voltage. No load input current max. 3% of the rated input current. The inrush-current max. 8 time of the rated input current. The rated output shall be between 3 KVA and 10 KVA, The rated output voltage max. 230 V a.c., single or three phase. Suthdown due to overloading is not premissible with these transformers. A monitoring device should be proides for checking the load (temperature or current) with an optical and acoustic signal.

Toroidal variable transformers
DIN VDE 0552
Toroidal variable transformers are used if the fine adjustement of alternating voltage from zero up to the maximum value is required.

Auto transformer
DIN VDE 0550 / 0570 DIN EN 61558
An auto transformer is a transformer in which input and output windings have common parts.There is no electrical isolation. A distinction is made between core power and rated power. The core power can be calculated from the transformation ratio and the rated power with the aid of the tables (auto transformater rating and example). A significant saving of materials is achievedwith one-coil winding because the core power is smaller than the rated power.

Step transformern
A step transformer is an auto transformer with tapping. This transformer Is suitable a in-line transformer for electical consumers. For example speed control of motors for ventilators.