Instrument transformers from WITT ensure an accurate measurement of input voltages and the input current, which are electrically isolated.
The transducers are used in direct current railway operations as well as in a stationary facility. The voltage of an external input is transmitted potential-free and it can be measured on the “hot” side of the traction power supply. This makes it possible to measure the existing voltage in the rail motor after the pantograph, as well as the voltage of a transformer station.
The entire electronics are surrounded by a fully insulating plastic. The 4 – 20 mA output is wired in such a way that 0 mA flows in the event of a defect and can be recognized as an error by the following sections.
The voltage to be measured is divided into voltage dividers (part of the device), a limited (temporary protection) and a filtered voltage. In the next step, this voltage is converted into a proportional frequency (60 – 800 kHz) and shifted through a completely galvanically isolated fiber optic cable. A subsequent frequency / voltage converter generates a proportional voltage, which – after the final filtering – is converted into electricity. The required auxiliary voltage is guaranteed by two separate measuring transformers, the primary and the secondary side.
| operating voltage
| 24 VDC
20 – 70 ° C
| 0 – 3 kV corresponds proportionally to 4 – 20 mA
up to 1 kHz (-3dB) +/- 1% of the final value
| Protection against contact
Qualification to exit
Input to the auxiliary voltage
Output to auxiliary voltage
| 12 kV