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In systems with dual power supply or two incoming lines and one busbar, forcing two/three MCCBs to "one in one out" prevents phase-to-phase short circuit, circulating current, and equipment damage caused by two power supplies being mistakenly parallel is the essential safety guarantee for dual power supply switching.
By using mechanisms such as levers, connecting rods, or steel cables, a hard constraint of "opening first and then closing" is achieved. When the closing side is locked, the other side cannot be operated without relying on electrical signals, and the control system remains effective even when it fails.
Supports opening/closing locking. During maintenance, lock the opening to prevent accidental closing, or lock the closing to avoid unauthorized opening. Combined with a padlock, it can meet the safety regulations of "locking and hanging".
The position of the operating handle is forcibly matched with the state of the main contact, reducing the risk of electric shock or misoperation caused by misjudgment of the state.
Independent of electrical circuits, resistant to electromagnetic interference, stable operation even in the event of power loss, suitable for scenarios such as hospitals, data centers, and rail transit that require high power continuity.
| Scene | Mechanical interlocking implementation methods | Core Objectives |
|---|---|---|
| Dual power supply (ATS) | The two MCCBs are interlocked, with only one circuit closed. | Protect against parallel short circuits in power supplies and ensure safe switching. |
| Two incoming lines and one bus tie | Three locks and two keys / hard interlock, any two units can be combined. | Busbars are operated in sections to prevent short circuits between sections. |
| Extractable MCCB | Handcart and circuit breaker operation interlock | Isolate the power supply during maintenance to prevent hot-plugging. |
| Load side maintenance | Circuit breaker locking + padlock | Prevent accidental closing and ensure personnel safety. |
| Characteristic | Mechanical Interlock | Electrical Interlocking |
|---|---|---|
| Reliability | Extremely high performance, purely mechanical, still effective even in the event of power failure or malfunction. | It relies on a secondary circuit and may fail in the event of a fault. |
| Response Method | Forced mechanical constraints, no intermediate state | There may be a switching delay due to the reliance on control signals. |
| Applicable Scenarios | Dual power supply, bus tie, lockable and tag-mounted | Automatic switching, remote control, and complex logic linkage |
| Compliance | Power supply departments give priority to approval, and compliance with mandatory standards is required. | It often needs to be used in conjunction with mechanical interlocks. |
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A: It physically forces two or three Molded Case Circuit Breakers (MCCBs) into a "one in one out" state. This prevents phase-to-phase short circuits and circulating currents caused by two power supplies being mistakenly closed at the same time.
A: Mechanical interlocking relies on physical parts like levers, rods, or cables instead of electrical signals. Because it is purely mechanical, it remains fully functional and reliable even during complete power loss or control system failures.
A: It allows operators to lock the circuit breaker in the open (or closed) state. When combined with a padlock, it satisfies safety regulations like "lockout and tagout" (LOTO), preventing accidental switch-ons while technicians work on the load side.
A: Yes. While automatic switching and remote operations rely on electrical interlocking, power regulations often require a physical mechanical interlock to be installed alongside it as a fail-safe backup.
A: This setup is used to run busbar systems in sections. The mechanical interlock (often using a three-lock, two-key system) prevents short circuits between sections by ensuring only safe combinations of breakers can be closed together.
A: Periodic inspections should be carried out to check for smooth mechanical movement, structural integrity of the connecting rods or cables, and to clear any debris. Regular cleaning and minor lubrication of pivot joints ensure the interlock remains reliable throughout its service life.
