HIGH PRECISION FLUXGATE CURRENT SENSOR
Dominggus Yosua Suitella.
1
, Dr. Ir. Djoko Windarto, MT.
2 1
Student and
2
Lecture of Electrical Engineering Department, Engineering Faculty, Diponegoro University Jl. Prof.Sudharto, Tembalang, Semarang
Abstract – Nowadays the necessity to measure currents in the industrial worlds has been growth to the most important
tools for proceedings controls. The classical approach of measuring current is by using a resistor and measuring the voltage drop across it. This method is fine for small currents however when the current levels increase to large values, it becomes
more difficult. This is because the power dissipation in the resistor increases with the current squared.
One solution for measuring large currents is by not directly measuring the current, but by measuring a property which is directly related to the current. By measuring the magnetic field around a conductor, the current level can be accurately
predicted. Fluxgate current sensor uses a high permeability magnetic core to detect magnetic fields produced by a current flow through a conductor. Prodrive B.V. develops and uses a sensor with one fluxgate winding. However there is a disadvantage
presented by this structure, that is the possibility of noise and ripple injection on the primary current measurement.
In this final project, a second fluxgate winding was used to cancel the induced spurious signal on the sensing resistor. The targeted specifications of the new design are spurious signal up to 50µArms, noise performance up to 50nAsqrtHz and
new operating switching frequency at 15kHz. Key Words
: Fluxgate, Current Sensor, Second Fluxgate Winding, Spurious Peak, Noise.
I. INTRODUCTION
1.1 Initial Condition
The company’s current sensor uses one fluxgate winding to detect the magnetic field. And in total the
sensor has 3 cores, 4 windings with their on purpose.
Control electronics
Transformer
Primary winding 4T
AC pick-up 300T
Fluxgate winding 200T
Compensation winding 1138T
Figure 1.1 Initial Condition
When the fluxgate is driven by square wave voltage, the voltage induces to the compensation
winding, makes a square waveform at the end of transformers. It also induced to the AC pick-up
winding but in opposite direction due to transformer polarity. The square wave signal from AC pick-up
windings then goes through the electrical circuit to the compensation winding. At the compensation winding,
both signals will add up each other. As the result there is spurious signal every harmonics switching
frequency.
Initially, the current sensor has following specifications:
- Unfixed switching frequency, around 43kHz.
- Has 4 winding with 3 cores
- Noise ≤ 1µAsqrtHz
- Spurious signal ≤ 150 µArms
1.2 Objectives The purposes of this project are:
1. Understand
with Fluxgate
current sensor
principle. 2.
Design a new system to reduce the spurious signal. Following are the target specification of
the project: -
5 windings transformer with 4 cores. -
Fixed switching frequency = 15kHz -
Noise ≤ 50nAsqrtHz -
Spurious signal ≤ 50µArms 3.
Implement the design into a prototype, transformer transformer design and control
board schematic and PCB design. 4.
Measure and qualify the finished prototype. 5.
Project documentation, related to the project. 1.3 Limitations
This thesis is only discuses about Fluxgate current sensor. Other magnetic based measurement
methods will only being explained briefly. 1.4 Company Profile
Prodrive B.V. was founded in 1993 by technical professionals from the Eindhoven University of
Technology. The organization consists of 3 main customer-oriented departments. The Mixed Signal
Group and the Digital Design Group are technological expertise centers active in the field of research and
development. Complex design trajectories are executed in cross-functional development teams.
The Electronic Solutions Group ESG covers the life cycle management of an electronic design.
The operations teams within ESG are managing the production, assembly and test of electronic products
and systems in the range from 1 up to 50.000 units per year.
Figure 1.2 Company Structure
II. LITERATURE REVIEW
2.1 Current Measurement Technology
