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    Intermittent duty
    :Intermittent duty

    The duty cycle (DC) is specified. In the operational pause, the temperature does not fall on the value of the environment.

    Determining the duty cycle
    :Determining the duty cycle

    With the ratio of intermittent duty capacity for playing time. The playing time consists of load and operating time break.

    Continuous operation
    :Continuous operation

    The transformer can be operated as long as desired at nominal load. The power ratings apply with us for continuous operation.

    according to DIN/VDE 0550   
    suitable for the rated power 
      - 2 kVAR - single-phase
    - 10 kVAR -three-phase
    according to DIN/VDE 0532  
    suitable for the rated power
      - 2 kVAR - single-phase
    - 10 kVAR -three-phase

    Line-and Commutating Reactors

    These reactors are installed between line and converter installations in order to increase the natural impedance of the line, to limit the commutation current, and to damp the interference voltage. A reac-tive voltage drop of 8.8 V/phase in case of 380 V, resp. 9,25 V/phase in case of 400 V corresponds to an impedance voltage ( Uk) of 4 %.

    Smothing- and Filter Reactors

    Reactors of this type are inserted in the direct current side of converter installations in order to reduce the ripple, to damp the harmonic waves, to limit the currents, and to damp the noise of the driving mechanism.


    Magnetic Energy Content of a Reactor

    W =  0,5 x L x I² (Ws)
    W =  energy in watt-seconds (Ws) 
    L =  inductivity in henry (H) 
    I =  current in ampere (A)

    The transformers contained in this catalogue are designed for 50 / 60 Hz. Losses, efficiency, and voltage drop are related to the frequency of 50 Hz. The reted power changes, if the frequency deviates from 50 / 60 Hz.

    Direct Current Power Supplies
    :Direct Current Power Supplies

    Rated Output Voltage

    The rated output voltage is the output direct voltage ( arithmetic mean ) in case of average load and rated  input voltage.


    Rated Power

    The maximal permissible output power in W ( watt ) is called the rated power and is stated as product of rated output direct voltage, and rated output direct current.


    Residual Ripple (RW )

    The proportion of the superimposed power-frequency voltage to the direct voltage. The value is stated as percentage.

    Limiting Values According to DIN 19240 for 24 V – Direct Current Power Supplies
    Upper limit of output voltage:

    Peak value: 30,2 Vs in case of unloaded output and a
    arithmetic mean:   28,8 V mains overvoltage of + 6%


    (The arithmetic mean can rise to the peak value, if a capacitor is used as protective element.)


    Lower limit of output voltage:

    Peak value: 18,5 Vs in case of rated output current and a
    arithmetic mean:    20,4 V mains undervoltage of – 10%
    Residual ripple: 5% in case of rated output current
    Insulation Class
    :Insulation Class

    This expression represents the ambient temperature and the insulation class.

    e.g.: T 40/B

    (In this case „40“ means the ambient temperature of 40°C and „B“ represents the insulation class.)

    Temperature Class of Insulation
    :Temperature Class of Insulation

    Size, loadability and lifetime of a transformer are determined substantially by the used insulating materials.


    According to IEC85 the temperature clsses of insulation are classified as follows:

    E  =  120° C

    B  =  130° C

    F  =  155° C

    H  =  180° C

    Short-circuit Withstand Capability
    :Short-circuit Withstand Capability

    The transformers are classified with regard to their capability to withstand short circuit as follows:


    Inherentlay short-ciruit-proof

    Non-inherently short-ciruit-proof



    Inherently short-circuit-proof transformers have no protective device. The capability to withstand short circuit is achieved by internal voltage drop. This can be realized by design, e.g. high-reactance transformers.


    Non-inherently short-circuit-proof transformers have a protective device which opens or limits the electric circuit in case of short circuit or overload. Fuses, excess-current circuit-breakers,thermal cut-outs, and PTC thermistors are customary protective devices.


    Non-short-circuit-proof transformers have no built-in protective device and have to be protected against overload by means of protective measures within the incoming line or the outgoing cable.

    Short-time operation
    :Short-time operation

    The load time is so short that the maximum end temperature is not reached. In the operational pause, the temperature drops to the value of the environment.

    Multi-winding Transformers and Tappings
    :Multi-winding Transformers and Tappings

    The stated powers are valid for one primary and one secondary voltage. Tappings up to 5 % do not require a larger core power. Secondary tappings are measured for the current of the highest voltage step.

    Several primary voltages, secondary tappings for full power, and some secundary windings with the necessary insulations require a larger core power.

    Vector Group (three-phase transformers)
    :Vector Group (three-phase transformers)

    The vector group indicates the winding connections and the ciruit arrangement of their phase angle to each other. Ist symbol consists of a capital letter for the input voltage, a small letter for the output voltage, and a code number. In case of brought-out neutral point „N“ resp. „n“ is added, for example YNyn0 – Dyn5 – YNa0.

    The following table represents a range of the most customary vector groups. Our standard types are designed according to vector group YNyn0 resp. Dyn5 in case of separate windings and according to vector group YNa0 in case of autotransformers.

    Three-phase transformers

    YNyn0   primarily = star connection
    N = lead-out star point
    secondary = star connection
    n = lead-out star point
    Dyn5   prinarily = delta connection
    secondary = star connection
    n =lead-out star point
    YNa0   primarily and secondary = star connection
    N =lead-out star point
    Protection Type
    :Protection Type
    IP 00   Open frame
    Without any protection against water and dust
    IP 23   protection against spray water
    Protection against particles > 12mm dia.
    IP 55   protection against water
    Protection against dust coverage
    Protection Class
    :Protection Class

    The stated protection class specifies the protective measures which secure a device against inadmissible touch voltage.


    Protection Class I

    Protection Class I characterizes devices, whose touchable metal parts, wich can be energized in case of a fault in the basic insulation, are connected to the safety earth terminal the connection of the safety earth terminal charcterizes the protective measure „protective earthing“.


    Protection Class II (totally insulated)

    Protection class II charcterizes devices, whose touchable metal parts are separated by means of an additional insulation from other parts, which can be energized in case of a fault in the basic insulation. They have no earth connection.


    Open transformers (IP 00) designated  for the installation in a device are only prepared for a special protection class. Transformers prepared for protection class II can also be used in devices of protection class I.

    Neutral Point Load
    :Neutral Point Load

    Vector Group: YNyn0 resp. YNyn6

    To avoid displacements of the neutral point and additional losses, it is only allowed to load the neutral point with the full rated current if the neutral conductor of the supply system is connected with the transformer-neutral point of the supply side. Does this not come true, only a load of 10 is permissible.

    The same is valid for the star-delta economy connection (YNa0).


    Vector Group: Dyn5 and Dyn II

    The neutral point can be loaded with the full rated current in case of these vector groups.


    Vector Group: Yzn5 or Dzn0

    The neutral point is also fully loadable. These vector groups are to recommend, if the load of the phases is unbalanced. But the additional expense for wirings and connection requires an extra charge.


    Mains Transformers and Power Transformers                                

    Transformers for general use with separate windings and a basic insulation between primary- and secondary winding.

    according to DIN/VDE 0550
    suitable for the rated power
      1 kVA - single-phase
    5 kVA - three-phase
    according to DIN/VDE 0532
    suitable for the rated power
      1 kVA - single-phase
    5 kVA - three-phase


    Isolating Transformers According to DIN/VDE 0551

    secure electrical separation the protective measure ,,protective separation” is fulfilled

    reinforced or double insulation


    rated output voltage: > 50 V

    rated power:     up to 25 kVA – single-phase 
        up to 40 kVA – three-phase

    Safety Isolating Transformers According to DIN/VDE 0551

    secure electrical separation the protective measure ,,safety extra-low voltage” is fulfilled

    reinforced or double insulation


    rated output voltage: = 50 V ( no-load operation )

    rated power:     up to 10 kVA – single-phase 
        up to 16 kVA – three-phase


    Overload - and Short – circuit Protection
    :Overload - and Short – circuit Protection

    Generally, built-in transformers are not protected against overload and short-circuit.

    Because of the high inrush current, which can be, possibly, the fiftyfold of the nominal input current, a protection by means of fuses or automatic ciruit-breakers is only possible in case of short-circuit but not in case of overload.

    A better protection can be achieved by using a circuit-breaker with a thermomagnetic release (starting circuit-breaker, power breaker), which can be adjusted to the primary rated current. As a result of increased winding temperature in case of  short-circuit or overload, another possibility is to insert temperature-controlled sensors in the windings. In this case an external switching device turning off (e.g. thermistor protection, thermal cut-outs, temperature controllers). To use or starting current limiters is also recommendable.


    The temperature caused by the specific heat capacity of the transformer under fixed operating conditions is called overtemperature. The difference between the nominal- resp. Ambient temperature and the temperature of the insulation class is the highest permissible overtemperature. The possible overtemperature has to be reduced because of hot spots and the reduction is dependent on the insulation class. Therefore, the permissible overtemperatures in case of an ambient temperature of 40° C are as fallows:

    Temperature Class of Insulation

    E = 75° C

    B = 80° C

    F = 100° C

    H = 125° C

    Ambient Temperature
    :Ambient Temperature

    The ambient temperature is the highest temperature which may surround the transformer under normal circumstances. If the transformer is built into a box, it is not alloed to go beyond the permissible ambient temperature, otherwise the load has to be reduced

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