Frequency
The rated frequency is the frequency for which the transformer is designed.
For inquiries and orders without frequency information, we assume a frequency of 50-60Hz and a sinusoidal input voltage.
Note 1:
A transformer cannot transform frequency. The frequency of the output voltage is identical to the frequency of the input voltage.
Note 2:
Transformers explicitly ordered for a frequency greater than 50Hz lead to smaller core types than 50Hz transformers of comparable performance. However, they cannot be operated - not even for testing purposes - with 50Hz and rated input voltage.
Note 3:
A transformer labeled with a rated frequency of 50Hz can be operated with 60Hz without any concerns.
Flat Transformer
The term "flat transformer" is commonly used for PCB transformers of the core type series UI30 and UI39.
Fixed-Mounted Transformer
A fixed-mounted (stationary) transformer is designed to be securely mounted during operation as specified by the manufacturer. It is either permanently mounted or weighs more than 18kg and lacks carrying handles.
A movable transformer can be moved while connected to the power supply. Transformers in the form of "plug-in power supplies" are also considered movable transformers.
An appliance transformer is specifically designed to supply power to certain devices or systems and is intended for use with them.
An embedded transformer is an appliance transformer designed for installation in a device housing that provides protection against electrical shock.
Unless otherwise expressly agreed, BREMER transformers are always executed as stationary transformers or appliance transformers and/or embedded transformers.
Farad (F)
SI unit of electrical capacitance
Unit: 1F = 1(A*s) / 1V = 1C / 1V (here C = Coulomb = electric charge)
Formula symbol: C
Michael Faraday: English physicist (1791 - 1867)
Charles Augustin de Coulomb: French physicist (1736 - 1806)
Input Voltage Range
The low-voltage (network voltage) standard values in Europe are established in IEC60038, being 230V (single-phase) or 3x400V (linked) with a tolerance range of +/-10%. BREMER transformers are designed to accommodate these tolerances unless otherwise specified or correction taps are intended.
Note: In user specifications, an input voltage indication of, for example, 230V +/-10% is often found. Clarification is then required as to whether this is intended to describe the input voltage range or express a desire for correction taps.
Therefore, we ask for precise formulation, e.g.,
- Input Voltage: 230V Input Voltage Range +/-10% or
- Input Voltage: 230V with taps for +/-10%
Note: BREMER transformers with positive taps are designed for a maximum input voltage according to the desired positive value. An additional addition with an input voltage range (tolerance range) would require agreement.
Input Voltage
The rated input voltage, also known as the supply voltage, is the voltage assigned to the transformer for the established operating conditions. In multiphase systems, this is referred to as the "line-to-line" voltage between the outer conductors.
See also: Multiple input voltages, multiphase systems
Throughput Power
Some transformer manufacturers use the term throughput power in autotransformers to indicate the output power. This is intended to highlight the difference from the "type" power or "core" power of the transformer.
Choke
Chokes for power applications are categorized into Alternating Current chokes (AC chokes) and chokes for Direct Current circuits (DC chokes).
AC chokes can be single or three-phase. Usually, these are choke coils with iron cores, with or without air gaps.
In the industry and universities, various terminologies are used to categorize chokes based on their application purposes:
Line Choke, Commutation Choke:
AC chokes for network fundamental frequency, mainly in a three-phase design, used to improve network current load (PFC) and to reduce the steepness of the flanks in the semiconductor valves of subsequent converters.
These chokes are primarily used in drive technology for a voltage drop uk = 4%, but uk = 2% is also common.
Motor Choke:
AC chokes, mainly three-phase, placed between the inverter output and the drive motor to shape the motor currents. These chokes extend the life of the motors and reduce noise. The required inductance values depend, among other things, on the length of the cables between the inverter and the motor.
Smoothing Chokes, DC-Link Chokes:
Direct current (DC) chokes, for example, for the DC link in converters between input rectifiers and output inverters. Also used for the excitation circuits of generators. The current dependency of this "smoothing element" must be considered in power supplies.
Compensation Chokes, Filter Chokes:
Filter chokes with matching capacitors, tuned to filter certain frequencies, or for (passive) compensation of reactive power loads.
Current-compensated Chokes:
These filter chokes have 4 (single-phase) or 6 connections (three-phase). They reduce asymmetric disturbances, influencing the useful signal only slightly.
Neutral Point Chokes:
Chokes for damping the currents and their steepness in the (via the choke) grounded neutral point in the case of earth faults in power supply networks (including railway power supplies).
Air Coils:
represent a special design. The advantage of their largely linear characteristic curve is offset by a large size and low inductance compared to iron core coils.
The essential characteristic of a choke coil is its inductance.
It must also be designed for the expected continuous and peak current. Instead of an inductance specification, a voltage drop at rated current can also be specified (see line chokes, uk...%). The rated frequency and the voltage to be considered for insulation technology are also required.
BREMER Transformer Series
At BREMER Transformatoren GmbH, we name our mains frequency series based on the standardized core laminations used, adhering to the traditions of our industry. The core laminations are designated as EI, UI, or 3UI, reflecting their external shapes.
Single-phase transformers up to about 650VA are available in various EI series.
Single-phase transformers ranging from 150VA to about 20kVA belong to the UI series.
Single-phase transformers above 20 to about 100kVA are categorized as ETN series, with their cores based on an in-house standard.
Three-phase transformers from 60VA to approx. 25kVA are called 3UI type series.
Three-phase transformers from 25 to max 180kVA are the DTN type series, these cores also originate from their own in-house standard.
Mains frequency PCB transformers are EE and EI types (EE20 ... EI66).
The so-called PCB flat transformers are called UI30 and UI39, as three-phase 3UI30 and 3UI39.
Product families of transformers, transformers and inductors for higher frequencies made of ferrite and other materials in all common forms from E to RM cores, we name as the core manufacturers do.
High-voltage and other special transformers have their own names.
You can find more information about core sheets in our flyer BREMER+GERTH_Kerne.pdf under Downloads.
Operating Mode
In continuous operation (CO), a transformer is operated indefinitely.
In short-time operation (STO), a (cold) transformer is operated for a certain period, allowing it to return to ambient temperature before the next cycle.
In intermittent operation (IO), a transformer is operated in a series of defined identical cycles.
It is practical for the user to specify their varying loads and the respective subsequent breaks for the "worst-case scenario" in minutes or hours. The indication of STO and IO in percent is often misleading.
BREMER transformers are always dimensioned for years of continuous operation unless otherwise specified.