3.3.5.3 Current Sensor Inputs

The PIC32CXMTSH-DB is compatible with various types of current sensors. It is possible to use an arbitrary combination of the following current sensors, subject to input voltage specifications:
  • Current Transformers (CT)
  • Shunt Resistors
  • Rogowski Coils
Warning: A shunt resistor must be placed in series with the line to be measured, then connected to the measurement inputs. The demonstration board is referred to neutral; therefore, a shunt resistor can only be used in neutral line. Using a shunt resistor to measure currents in lines 1 or 2 will damage the board, and it is dangerous for the user.
Attention: Note that this kit does not include any CT, Rogowski coils or Shunt current sensors.
Each current sensor (CT, Shunt or Rogowski Coil) must be connected to two positions of the same connector. The current input lines are distributed to an A/D converter through a configurable filter whose function is to adapt the chosen current sensor. Both inputs have the same filter configuration and layout. Their ground reference is GND.
Important: By default, the PIC32CXMTSH-DB board is configured to host a current transformer. The board is populated with resistors R63, R65, R67 and R69 of 1.62Ω to fit a standard 200A CT with 1:2000 turn ratio. Using default installed burden resistors of 3.24Ω (2 × 1.62Ω), a 2000:1 CT ratio will allow a max of 240A. (240 Arms × √2 × 3.24Ω/2000 = 0.55 Vpk).
Figure 3-13. IPx and INx Current Sense Schematic
Some test points close to the A/D converter inputs allow monitoring the input voltage value at the A/D converter inputs corresponding to the current:
  • TP29: IP1 input measurement referring to GND
  • TP33: IN1 input measurement referring to GND
  • TP30: IP2 input measurement referring to GND
  • TP34: IN2 input measurement referring to GND
Figure 3-14. IPx and INx Test Points