Two Different Jobs, Two Different Coils
A vacuum circuit breaker's operating mechanism is opened and closed electrically through two separate solenoid coils that perform opposite jobs. The closing coil is energised to release the mechanism's stored energy (usually from a charged spring) and drive the breaker contacts closed. The trip coil (also called the shunt trip coil) is energised to release a latch and allow the mechanism to open the contacts, whether that command comes from a protection relay, a control switch, or a manual trip pushbutton.
Why the Difference Matters for Protection
The trip coil is the direct electrical interface between the protection relay and the breaker — when a relay detects a fault, it energises the trip coil to open the breaker and clear the fault. This makes the trip coil circuit safety-critical: many breakers use two independent trip coils for redundancy, so that a fault in one trip circuit does not leave the breaker unable to open. The closing coil, by contrast, is involved in restoring supply, not in fault clearance, and does not usually carry the same redundancy requirement.
How to Tell Them Apart When Ordering a Spare
- Check the wiring diagram or terminal markings — trip and closing coil terminals are usually separately labelled in the breaker's schematic (commonly something like "CC" for closing coil and "TC" or "Y" for trip coil, though exact conventions vary by manufacturer).
- Note the control voltage — both coils have a rated control voltage (for example 110 V DC, 220 V DC, or 240 V AC), and it must match your station battery or control supply. The two coils on the same breaker are not always the same voltage.
- Physical position — on many designs the two coils sit in different, clearly separated locations within the mechanism housing; comparing against the manual or a parts diagram avoids guessing.
- If unsure, send a photo — a clear photo of the coil, its wiring, and any visible marking lets a supplier confirm which one it is before you order.
Ordering the Right Part
Always order using the breaker's make, model, and control voltage rather than the coil's physical appearance alone, since coils for different voltages can look identical. See our guide on finding the right spare part number for the full checklist.
Browse VCB trip coils and VCB closing coils, or send your breaker model and control voltage through an RFQ and we will help confirm the right one.