T&R Filter Unit 100ADM-F

  • Forces test current to a sinusoid
  • Improves timing accuracy when testing electro-mechanical relays
  • 0.25A – 100A ranges
  • High overload capability
  • 50/60Hz operating frequency
  • High efficiency


The 100ADM-F Filter Unit reduces the level of current harmonics when testing electro-mechanical protection relays. It is designed for use with our range of secondary injection test sets.

All electro-mechanical protection relays have iron cores that saturate and distort the test current under high overload test conditions. The distortion causes significant errors in the measured trip time of these relays during testing. Distortion of the waveform can be a particular problem with disc induction type over-current and sensitive earth fault relays.

For example, testing a CDG11 disc induction over-current relay without a filter causes significant timing errors. The results bellow show the errors for a 1.3s 1A CDG11 over-current relay on its 0.5A plug setting, tested at 5A.

100ADM-F Table

The 100ADM-F Filter Unit has nine current ranges covering 0.25A to 100A and is supplied in an insulated case, complete with protective cover and carrying strap.

Range Continuous rating 5 min on/ 15 min off
0.25A 0.125A 0.25A
0.5A 0.25A 0.5A
1A 0.5A 1A
2.5A 1.25A 2.5A
5A 2.5A 5A
10A 5A 10A
25A 12.5A 25A
50A 25A 50A
100A 50A 100A

The unit may be used at either 50Hz or 60Hz, selectable by a switch on the front panel. The lower ranges (0.25A-50A) are selected by a switch, and the highest current range is selected by a terminal. A current monitoring output is provided on all the filter units that provides an output of 0-100mA corresponding to the rated current for the range. Table below gives the impedance in ohms of the filter unit against frequency on each range.

Range Impedance (Ω)
50Hz 150Hz 250Hz 350Hz
0.25A 880Ω 17.5kΩ 30.4kΩ 41.5kΩ
0.5A 220Ω 4.38kΩ 7.65kΩ 10.3kΩ
1A 47.7Ω 950Ω 1.65kΩ 2.25kΩ
2.5A 7.8Ω 150Ω 250Ω 360Ω
5A 1.94Ω 38Ω 65Ω 90Ω
10A 510mΩ 9.5Ω 16.5Ω 22.5Ω
25A 85mΩ 1.5Ω 2.5Ω 3.6Ω
50A 22mΩ 380mΩ 650mΩ 900mΩ
100A 5.5mΩ 95mΩ 165mΩ 225mΩ



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