Reliable measurement of DC currents up to the kA range with a high level of accuracy
Facts
- Precise and long-term stable measurement of DC currents
using shunt resistors - For currents up to 15 kA,
up to 8 kA with standard devices - Low shunt voltage / small types possible
with special shunt isolators - Shunt accuracy:
class 0.5, optionally class 0.2 - Shunt isolator / transmitter with 0.1 % gain error
- High overload capacity
without trailing measurement errors - No influence from adjacent wires
due to the measuring principle - Galvanic isolation between the power unit and control unit
up to 3.6 kV working voltage /15 kV test voltage - Conversion to standard signals,
±20 mA, ±10 V, 4 to 20 mA - MTBF of 96 years
for the complete current measurement system - 5-year warranty
Maconic shunt resistors are the result of many years of experience in the design and production of such resistors. They are carefully manufactured using high-quality materials. The resistor bars are made of manganin, a special manganese-copper-nickel alloy, so that a very low temperature coefficient is achieved. Dimensioning and mechanical construction are selected so that the resistors only heat up slightly up to the rated current.
The shunt resistors and associated shunt isolators achieve very good long-term stability, which guarantees the specified accuracy over the normal periods of application of many years. Current peaks do not cause any offset or drift. Protection equipment based on current measurement benefits from the reliability and long-term stability of the measurement and achieves a particularly high level of safety performance.
The Application
In many areas of applications the use of shunt resistors has established itself as a reliable, precise and long-term stable solution for continuous measurement of DC current. The low voltage drop across the shunt resistor is directly proportional to the flowing current. It is sensed by a specially designed shunt isolator, where it is converted to a standard signal and output as a measure of the current for further processing in controllers or displays.
DC currents are measured in a diverse range of applications, including photovoltaics, power supply of public transport systems, control of motors and generators, DC buses of inverters, welding equipment, and generally in systems with high DC currents.
The Task
The currents to be measured are associated with system voltages (potentials) which must be safely separated, i.e., galvanically isolated by the shunt isolator. Here, it is important that the voltage measurement is not affected by common mode influences. This can be achieved even for shunt voltages as low as 60 mV by suitably designed shunt isolators. Higher shunt voltages are not necessary with high-quality shunt isolators and because of the physically larger shunt resistors they are generally not desired.
Particularly for high currents, the loss in the shunt resistor must be very low to prevent excessive heating. In any case, the resistance of the shunt should be as constant as possible with changing temperatures. The shunt resistor must be insensitive to corrosion or other environmental effects. Here, special attention must be paid to material and workmanship.
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