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Series MRA/4000 Separation and control output 0/12/18/24V

Shell-type Single-phase control transformers

  • Converter transformers built according to standards IEC 61558–2-1
  • Dual voltage input 230/400 V AC
  • Rated voltage outputs 0/12/18/24V
  • Frequency 50/60 Hz
  • Insulation material group F
  • Ambient temperature max. 40 °C
  • Degree of protection IP 00
  • Class I built with M5 ground
  • Zinctropicalized steel fixing angles
  • Varnish dipped and oven dried
  • On stock

This series is particularly used when a 24V in AC and a continual 24V in DC supply is needed, rectifying and filtering the 18V AC output. Please take special care in not connecting contemporarily to earth, both the output AC end and the rectified voltage minus (-), to avoid short circuiting of the rectifying bridge (Wiring Diagram – fig. 1).fig. 1).

If a full-wave center tap rectifying system is needed, the main output socket (12V) becomes the reference point and the two extremes of the winding are connected to the diodes, to obtain 12V DC (Wiring Diagram – Fig. 4)

Maximum power is guaranteed on the 24V AC output. The maximum limit of the withdrawable current, calculated by dividing the rated power output by the rated voltage (24V AC), must not be exceeded on each output.
. For a contemporary current withdraw on more outputs, the sum of the output currents must not exceed the above limit. For example : Max. 100VA/24V= 4,16A are withdrawable from 24V AC output of 100VA rated transformer; if there is an AC load which only absorbs 1,5A from 24V AC output, 4,16A-1,5A= 2,66A can be withdrawn from other outputs.

If 18V Ac output is full-wave rectified and filtered with capacitors to obtain 24V DC, 2,66A/1,5= 1,77A DC are available, as the effect of the capacitive filter load causes an increase of rms current absorbed from the transformer.

If 24V DC are needed, a full-wave center tap rectification can be made by using “0V- 12V-24V” terminals.

When using a capacitive filter 2,66A/(1,5*0,786) = 2,26A DC are available