Introduction
Current transformers, also commonly known as Current Sensors, are the devices used to measure the current running through a wire. The current sensors use a magnetic field to detect the current and generate a proportional output. These devices can be used with both AC and DC. An essential characteristic of the current sensor is that it allows us to measure current passively, that is, without interrupting the circuit by just placing them around the conductor whose current we want to measure.
How do Current Sensors work?
We place the current sensor around the conductor whose current we want to measure. When current flows through the conductor, it creates a proportional magnetic field around the conductor. Here comes the role of the current sensor. They use this magnetic field for the current flow. If the current transformer is being used to measure AC, the sensor uses inductive technology. The current that changes its potential is only termed an Alternating Current, and this change in potential causes the magnetic field to continually collapse and expand. In the AC measuring current sensor, a wire is wrapped around a core. The magnetic field that the flowing current has produced induces a proportional current or voltage in the wire within the current sensor. This current or voltage is shown as an output on a meter connected to the sensor, which translates it into the amount of current flowing through the given conductor. Current Sensors used for measuring DC also work similarly, except that they rely on Hall Effect technology to operate.
Current transformers are either step-up or step-down, keeping the current same. Those sensors that step up or step down are referred to as transformers. Sensors typically consist of two coils - primary and secondary coil. The primary coil is where the current passes and the coil in which voltage is induced in the secondary coil.
Current sensors for measuring DC are capable of measuring both DC and AC. The DC measuring current sensors are also termed Hall Effect Sensors. These sensors consist of a core, a Hall effect device, and signal conditioning circuitry. They now operate based on the Hall Effect. Hall Effect is a phenomenon that says that when current moves through a conductor, it creates a magnetic field, and now if this conductor is positioned within some other magnetic field, the magnetic field produced due to the flow of current interacts with the outside magnetic field. This interaction creates a voltage on the conductor, which is proportional to the amount of current running through it and thus can be measured. The turn of the ratio of a transformer is the number of turns in the secondary coil windings to the number of turns in the primary coil windings. Whether a transformer steps up or down is decided by this ratio. When the number of turns on the secondary winding is greater than that of the number on the primary winding, the voltage on the secondary is higher and it is a step-up transformer.