When discussing overload monitoring, the term "current transformer" is always unavoidable. Many people get a headache just hearing the name, thinking it's some kind of high-tech gadget. Actually, it's just a "caliper" on a power line, responsible for measuring current. Understanding this is key to understanding a large part of the entire system.
The function of a current transformer is to convert the actual current flowing in the wire into a small signal that the control system can read. If the current is too small, the controller won't read it accurately; the current transformer acts like a transformer, "shrinking" a large current into a controllable small current, essentially providing the monitoring system with a ruler, letting it know exactly how much electricity has flowed through the circuit. Without it, the control device is blind.
The first thing to do when selecting a current transformer is to measure the orifice diameter. Current transformers are fitted onto the power line; if the orifice is too small, it won't fit; if it's too large, it will wobble. Before buying, you need to know the wire diameter and the width of the busbar, and provide the manufacturer with the appropriate orifice diameter model. Don't skip this step; installation problems on-site are the biggest headache.
The second thing is to distinguish between open-type and closed-type current transformers. Closed-type current transformers are a complete loop. During installation, the wires must be unplugged, threaded through, and reconnected. This is not only troublesome for retrofitting old cabinets but also requires a power outage. Open-type transformers can be pried open, threaded onto the wires, and then closed, without unplugging the wires or interrupting the power. This is why retrofit projects prefer open-type transformers. Hangzhou Qiling's current transformers follow this design principle-just snap them on.
The third thing is accuracy. The accuracy of the current transformer directly affects the accuracy of the monitoring data. A lower-quality transformer can result in significantly inaccurate current readings, rendering alarm thresholds ineffective. When choosing, don't just look at the price; opt for a higher accuracy level. Combined with high-precision current sampling in the control device, the data will be more valuable.
Another detail easily overlooked is the wiring direction of the current transformer. If installed backwards, the phase of the sampled current signal will be reversed, leading to incorrect readings. Reputable manufacturers will clearly mark the direction before shipping; simply follow the instructions during installation. This is why it's recommended to buy the entire system as a set, ensuring better compatibility between components and avoiding haphazard assembly.