A capacitor switching contactor is a heavy-duty electromagnetic switch specifically designed to handle the high "inrush current" that occurs when switching large capacitor banks. Unlike a standard motor contactor, it features pre-charge resistors (the wires seen at the top) that briefly enter the circuit first to dampen the initial electrical surge, preventing damage to the contactor and the capacitors.
When a capacitor bank is turned on, it initially acts like a short circuit, drawing a massive spike of current that can weld the contacts of a normal switch together. The CJ19 series is engineered to eliminate this risk.
- Arc-Suppression Mechanism:
- Pre-Charge Resistors: The black looped wires at the top are current-limiting resistors. When the contactor is activated, these resistors make contact milliseconds before the main power contacts. This "soft start" limits the inrush current to a safe level.
- Automatic Disconnect: Once the main contacts are fully closed, the resistors are automatically disconnected from the circuit to prevent them from overheating during normal operation.
- Key Components & Terminals:
- Main Power Terminals: Labeled L1, L2, L3 (top) and T1, T2, T3 (bottom), these carry the heavy three-phase load.
- Auxiliary Contacts: Labeled 13 NO/14 NO (Normally Open) and 21 NC/22 NC (Normally Closed), these are used for signaling, such as turning on an indicator light or providing feedback to a controller.
- DIN Rail Mounting: The metal bracket on the back allows it to be easily snapped onto a standard 35mm DIN rail inside an electrical panel.
- Applications:
- Primarily used in Automatic Power Factor Correction (APFC) panels for industrial facilities.
- Essential for managing the reactive power of large motors and transformers, which helps reduce energy costs and improves grid stability.
