Industrial re-chargeable battery systems are used to provide primary power for vehicles and back-up systems for critical equipment, like cell phone base stations and other communications equipment. DC current flows in one direction during charging and in the opposite direction during battery operation. Traditional Current Transformers do not work with DC current and using current shunts has been the solution. The shunt operates by producing a voltage potential across its terminals according to Ohm’s law. It suffers from a number of serious disadvantages:
- Terminals can rise to the potential of the DC circuit.
- The signal produced is usually 50 – 100mV at full rated current and must be isolated and amplified to a higher level signal (typically 4-20mA) to be of use to an industrial monitoring or control system.
- The shunt dissipates power according to the square of the current flowing through it. This manifests itself as a loss of power or an insertion loss.
Forget the shunt and instead simply pass the current carrying conductor through the aperture of an NK Technologies’ DC Current Transducer. There is no insertion loss and the 4-20mA signal is fully isolated from both the DC current being measured and the power supply. The bipolar option also accommodates the change in direction of current flow.