Working Principle and Magnetic Saturation Issues of Hall Electrical Current Sensors

Hall electrical current sensor is based on the principle of magnetic balance Hall, according to the Hall effect principle, the control current is sent into the current end of the Hall element, and a magnetic field intensity of B is applied in the normal direction of the Hall element plane. Then an electric potential VH is generated perpendicular to the direction of the current and magnetic field (i.e. between the Hall output terminals), which is called the Hall potential, and its magnitude is proportional to the product of the control current and magnetic field intensity.

The principle of Hall electrical current sensors

Hall device is a kind of magnetic-electric conversion device made of semiconductor materials. If the control current IC is input at the input end, when a magnetic field B passes through the sensing surface of the device, a Hall potential VH appears at the output end. The magnitude of Hall potential VH is proportional to the product of control current IC and magnetic flux density B. Hall sensor low-power is made according to the principle of Hall effect and applied to Ampere's law, that is, a magnetic field proportional to the current is generated around the current-carrying conductor, and the Hall device is used to measure this magnetic field. Therefore, non-contact measurement of current is possible. By measuring the magnitude of Hall potential, the magnitude of current-carrying conductor current is indirectly measured. Therefore, current sensor has undergone electrical-magnetic-electrical insulation conversion.

The problem of magnetic saturation of closed-loop Hall electrical current sensors

The problem of magnetic saturation of open-loop Hall electrical current sensor is relatively simple. In comparison, the problem of magnetic saturation of closed-loop Hall current sensor seems to be incomprehensible, because when the closed-loop Hall current sensor works normally, the magnetic flux in the magnetic core is zero. Under the condition of zero magnetic flux, naturally there will be no saturation. However, this can only be true under normal working conditions. In fact, even in the case of electromagnetic current transformer or open-loop Hall current sensor, magnetic saturation occurs under abnormal working conditions such as overload, low frequency, and heavy load. Under normal working conditions, magnetic saturation does not occur. It can be seen from the working principle of closed-loop Hall sensor that zero magnetic flux is based on the prerequisite that the magnetic field generated by the compensation winding of the secondary side can counteract the magnetic field generated by the primary conductor. So, can closed-loop Hall current sensor maintain this zero magnetic flux under any circumstances? Obviously not.

When the sensor is not powered, the compensation winding on the secondary side does not generate current. At this time, the closed-loop Hall current sensor is equivalent to an open-loop Hall current sensor. As long as the primary current is large enough, magnetic saturation will occur. When the normal power supply is on, the primary current is too large. This is because the current that can be generated by the secondary compensation winding is limited. When the magnetic field generated by the primary current is greater than the maximum magnetic field that the secondary compensation winding can generate, magnetic balance is broken, and there is magnetic field passing through the magnetic core. When the primary current continues to increase, the magnetic field in the magnetic core also increases. When the primary current is large enough, the closed-loop Hall current sensor enters a saturation state.

Compared with electromagnetic current transformer and open-loop Hall current sensor, the phenomenon of magnetic saturation of closed-loop Hall sensor is not easy to occur, but it does not mean that it will not happen. Improper use or long-term overload can also cause magnetic saturation.