Watt (W)
SI unit of power
Unit: Watt 1W = 1V*1A = 1J/s (At the transformer we indicate the apparent power Volt-Ampere VA)
Formula symbol: P
James Watt: Scottish engineer (1736 - 1819)
Volt (V)
SI base unit of electrical voltage
Unit: Ampère 1V = 1W/1A
Formula symbol: U
Alessandro Giuseppe Antonio Anastasio Volta: Italian physicist (1745 - 1827)
Ambient Temperature
The rated ambient temperature is the highest temperature at which the transformer can be operated continuously under specified operating conditions.
A temporary overshoot of +10°C is generally permissible. Otherwise, the necessary cooling cannot be guaranteed.
Rated Power Equivalent
The term "Typenleistung," or Rated Power Equivalent, doesn’t refer to a direct electrical size. It is used as a guideline to estimate the space requirements and weight of transformers, representing a common equivalent between a transformer core type and electrical power under simplified conditions (e.g., 50Hz, ta=40°C).
The actual output power that can be achieved with a particular core type depends on various factors, such as the ambient temperature, maximum permitted component temperature, core material, operating mode, cooling situation, number of output windings, number of primary voltages, maximum open-circuit voltages, insulation requirements (type of transformer) and others.
Note:
Users should note that the desire for multiple input voltages often leads to a larger transformer type compared to a transformer of identical output power designed for only one input voltage. A "universal transformer" is thus often not economical. Likewise, designing the transformer for a higher than realistically expected ambient temperature leads to larger types.
See also: Rated power, Throughput power
Dry-Type Transformer
Transformer in which the windings and core are not in an insulating liquid.
All BREMER transformers are dry-type transformers.
Isolating Transformer
An isolation transformer is a transformer with a protective separation between the input and output windings. Isolating transformers for general applications, single-phase up to 25kVA and multi-phase up to 40kVA, are usually designed according to EN61558-2-4. If agreed between customer and supplier, this standard can also be applied to isolating transformers without limitation of the output power.
In contrast to the mains transformer (according to EN61558-2-1), the isolating transformer has so-called "double or reinforced" insulation in addition to the basic insulation. (Some types may also have a combination of the basic insulation with a shield winding between the input and output winding in its place).
Note:
A "transformer with separate windings" (ugs.) is a mains transformer and has basic insulation.
See also: Mains transformer
Tesla (T)
SI unit for magnetic flux density
Unit: Tesla 1T = 1Vs/1m²
Formula symbol: B
Nikola Tesla: Croatian-American physicist (1856 - 1943)
Temperature Limiter
Transformers must be suitably protected against impermissibly high temperatures in the event of overload or short circuit. A number of protective devices (fuses, magnetic and thermo-magnetic switches, overload releases, temperature limiters, etc.) are possible and suitable depending on the application.
A temperature limiter cannot be adjusted by the user and, if a transformer is not used as specified, limits its temperature by opening the circuit or reducing the current.
A self-resetting temperature limiter ("temperature monitor") restores the current flow as soon as the transformer has cooled down. A temperature limiter that does not reset automatically also requires manual intervention.
A "thermal fuse" or "temperature fuse" must be replaced after it has responded once. Usually, this involves replacing the entire transformer.
Small transformers - especially small print transformers - in a conditionally short-circuit-proof design are often equipped with thermal fuses permanently built into the transformer. After an overload or short circuit, the transformer must be replaced.
Alternatively, automatically resetting bimetal thermal switches ("temperature monitors") can be installed, but these require a minimum size for space reasons and a certain unit value for commercial reasons.
Temperature monitors, for example bimetal normally open or normally closed contacts, can be installed in the windings and their contacts routed to terminals. After installing the transformers in a system or equipment, the user has an easy-to-handle signal for control or warning purposes or for emergency shutdown.
See also: Short-circuit strength
Leakage Transformer
Leakage transformers are designed to have reduced coupling between the input and output circuit windings and increased leakage field, which is normally undesirable on fixed-coupled transformers. Operating curves with high open-circuit voltages and defined current-voltage values at load can be realised.
Leakage transformers can also be designed as absolutely short-circuit-proof transformers for higher power ratings, but they represent a very complex special design.
Note:
Typical applications for leakage transformers are gas discharge lighting ("neon lights") with high ignition voltages and subsequent limitation of the current in the gas path which now represents a "short circuit".
For some converter circuits, transformers with increased short-circuit voltages are required, which, depending on the level of the short-circuit voltage, can also already be referred to as leakage transformers.
By combining an AC choke and a fixed-coupled transformer, circuit characteristics comparable to a leakage transformer can be produced.
Because of the complex engineering work involved, leakage transformers are commercially unfavourable for single units and very small series.
Autotransformer
An autotransformer is a transformer where the input and output voltages are derived from a common winding, leading to smaller and more cost-effective sizes. In part, this results in significantly smaller and thus more cost-effective sizes.
ATTENTION: There is no galvanic isolation between input and output circuit!
Note:
It is the user's responsibility to check whether a transformer without galvanic isolation may be used. Among other things, it must be considered whether the insulation level of a device connected to the output of the autotransformer is sufficient.
Example: Operation of a 115V unit on the European 230V mains: We would generally advise against using this unit with an autotransformer and recommend a transformer with separate windings.
An autotransformer, also known as a "Spartransformator" in German.
See also: rated poweer equivalent, throughput power