Wichit Sirichote, wichit.sirichote@gmail.com
Build a circuit that converts control voltage into +/-5A current source. Designed for testing 5A CT.
This circuit is designed for testing the 5A Current Transformer (CT) that used in AC energy meter. We can find the transfer function beween 0-5Arms input and the output EMF from the CT easily. This circuit provides a 100% pure sine wave of the current waveform of +/-5Arms from the reference input signal. The circuit is built with the power operational amplifier, OPA541AP. The reference signal, Vin is adjusted by R3, 25 turns trim port. The output of U2, OPA541 drives the load with +/-5A. The load current is returned to R2, 0.5Ohm resistor providing the feedback signal to the inverting input of the OPA541. The control input voltage is +/- 5A*0.1Ohm, or +/-0.5V to provide +/-5A output.
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| Figure 1: Schematic of the +/-5A Voltage Controlled Current Source. |
The power opamp, OPA541 needs the heatsink. Figure 2 shows the board built with universal PCB. The wire for 5A must be large size. Trim POT is blue one, 25 turns. The Non Henry Load (NHL) resistor, R2 is placed near the terminal.
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| Figure 2: The board is built using universal PCB, mounting the OPA541 with the heatsink. |
