BD Union

1. Is it necessary to detect single-phase current or three-phase current? There are usually two forms of current transmitters that can be used to detect single-phase or three-phase current. For example, "I" in BD-AI represents a single-phase current transmitter; The '2' in DB-AI2 represents a 2-channel current transmitter.

2. Range of transmitter input current - Due to the large range of actual load current changes, to adapt to this situation, we usually use current transformers to convert high currents into small currents of 1A or 5A. So, the input of the current transmitter is usually selected based on the secondary current of the current transformer. For example, if the secondary current of the current transformer is 5A, the input current of the current transmitter can also be selected as 0-5A. The range of variation for output DC signals - Currently, the international standard for output signals usually uses DC4-20mA. Of course, the output DC signal can also use DC voltage (such as DC0-5V, etc.), which should be matched with the input of the instrument or automatic control device behind the current transmitter.

3. Specification of auxiliary power supply - In order to accurately detect changes in input current and output DC signals that vary linearly with the input current, an auxiliary power supply for the current transmitter is usually required. Usually, the most commonly used is the easily obtainable AC220V. You can also choose a DC power supply, such as DC24V, etc. It should be noted that there are some current transmitters that claim to not require an auxiliary power supply, known as "passive" current transmitters. For this type of current transmitter, careful selection should be made. The so-called "passive" type does not mean that it does not require a power supply, but rather that the working power is provided by the instrument behind the output signal of the current transmitter. It is "eating the instrument power supply behind the transmitter", which naturally increases the burden on the acquisition instrument behind the transmitter. There is also a type of "passive current transmitter" that uses the secondary current of the current transformer as the power supply for the transmitter. The disadvantage of this type of transmitter is that when the load current is small, the output current of the current transformer is naturally small, and the energy provided to the transmitter is also reduced. At this time, the current transmitter will produce nonlinear errors, resulting in errors in the transmission of current signals. Therefore, this type of transmitter also needs to be carefully adopted.

4. Input overload capacity of current transmitter - When the load current is overloaded or the system malfunctions, the current transmitter usually bears a very large overload current. In this situation, the ability to withstand large overload currents has become an important indicator for measuring the performance of current transmitters.