Page 8 - Current & voltage sensors catalog

Three technologies for measuring current

1. Closed loop
1
Hall effect technology

Principle
ABB current sensors based on closed loop Hall effect technology are electronic trans- Sensor Power supply
formers. They allow for the measurement of direct, alternating and impulse currents, with I P
galvanic insulation between the primary and secondary circuits. + + V A
The primary current I P flowing across the sensor creates a primary magnetic flux. N P R M
M 0V
The magnetic circuit channels this magnetic flux. The Hall probe placed in the air gap N S
V M
of the magnetic circuit provides a voltage proportional to this flux. _ _ V A
The electronic circuit amplifies this voltage and converts it into a secondary
I S G108DG
current I S. This secondary current multiplied by the number of turns Ns of secondary
winding cancels out the primary magnetic flux that created it (contra reaction). The The secondary output current I S is there-
formula N P x I P = N S x I S is true at any time. The current sensor measures instantaneous fore exactly proportional to the primary
values. current at any moment. It is an exact rep-
lica of the primary current multiplied by
the number of turns N P/N S. This second-
ary current I S can be passed through a
measuring resistance R M. The measur-
ing voltage V M at the terminals of this
measuring resistance R M is therefore
also exactly proportional to the primary
current I P.

Advantages Applications
The main advantages of this closed loop Industry Railway
Hall effect technology are as follows: Variable speed drives, Uninterruptible Main converters, auxiliary converters
– Galvanic insulation between the Power Suppliers (UPS), active harmonic (lighting, air conditioning), battery char-
primary and secondary circuits filters, battery chargers, wind genera- gers, choppers, substations, mining, etc.
– Measurement of all waveforms is tors, robotics, conveyers, lifts, cranes,
possible: direct current, alternating solar inverter, elevator, etc.
current, impulse, etc.
– High accuracy over a large frequency
range (from direct to more than 100 kHz)
– High dynamic performance
– High overload capacities
– High reliability.

6 | ABB