Disconnector Switches Load Break | 20A-160A | AC-23A | Panel Mount DIN Rail

Fuse-Switch Combination Main Incoming Unit

A factory main switchboard uses a UKP4 1250A disconnector switch as the incoming device, with upstream NH fuses at the supply authority’s service connection providing the overcurrent and short-circuit protection. The disconnector switch provides the local isolation and operational switching function: the plant electrician can isolate the entire switchboard for annual maintenance by switching the UKP4 to OFF and padlocking the handle. The AC-23A rating allows the switch to break the full plant load if the upstream fuses have not yet operated (for example, during a controlled shutdown before the supply authority isolates the service). The visible double-break isolation gap provides positive confirmation of isolation before work begins on the switchboard busbars.

Dual-Supply Bus-Coupler Application

A hospital’s dual-supply switchboard uses a UKP4 800A disconnector switch as the bus-coupler between the two busbar sections. During normal operation with both utility supplies healthy, the bus-coupler is open and each supply feeds its own busbar section. If one supply fails, the affected incomer disconnector is opened, the bus-coupler is closed, and the entire hospital load is supplied from the remaining healthy incomer. The UKP4’s AC-23A rating ensures it can safely close onto the busbar with the motors and transformers on the de-energized busbar section drawing inrush current. The door interlock and padlock facility allow the maintenance team to lock the bus-coupler in either the open or closed position depending on the maintenance configuration.

Motor Control Center Incoming Disconnector

A motor control center serving a production line uses a UKP4 400A disconnector switch as the main incoming device, with upstream fuses at the main switchboard providing the overcurrent protection. The disconnector provides the single-point isolation for the entire MCC, allowing the production line to be safely de-energized for mechanical maintenance or process changeover. The auxiliary contact signals the PLC that the MCC incoming supply has been disconnected, and the PLC prevents the motor starters from attempting to close their contactors while the disconnector is open. The UKP4’s AC-23A rating is well above the production line’s starting inrush (approximately 1500A for a typical 400A MCC with multiple motors starting sequentially), ensuring reliable switching without contact welding.

Capacitor Bank Switching Application

Power factor correction capacitor banks use UKP4 disconnector switches as the main incoming device, with the AC-23A rating specifically covering capacitive load switching (the making capacity for capacitive loads can be 20-30 times rated current due to the inrush when a discharged capacitor bank is connected to the busbar). The UKP4 is selected with a current rating of at least 1.43 times the capacitor bank’s rated current (to account for the capacitor tolerance, harmonic current and supply voltage tolerance per IEC 60831). The spring-assisted quick-make mechanism ensures the contacts close at full speed through the pre-arcing region, minimizing contact erosion from the capacitive inrush current that flows before the contacts mechanically touch.

Generator Incomer Disconnector for Load Testing

A standby generator installation uses a UKP4 630A disconnector switch as the generator incomer, providing isolation during generator maintenance and the operational switching for the monthly load test. During the test, the utility incomer is opened, the generator is started, and the UKP4 is closed to connect the generator to the facility busbar. After the test, the UKP4 is opened to disconnect the generator before the utility incomer is reclosed. The disconnector switch is preferred over a circuit breaker in this application because it is mechanically simpler, has no trip unit to test and calibrate, and the visible isolation gap provides clear confirmation that the generator is disconnected from the busbar before the utility supply is restored.

Integrate Disconnector Switches into Your Switchboard

• Application Engineering: Our switchboard engineers specify the UKP4 rating, configuration and mounting for your single-line diagram.
• Type-Test Package: Obtain complete test documentation for your switchboard IEC 61439 verification.
• OEM Supply: Source UKP4 switches pre-assembled with handles, interlocks and auxiliary contacts for your switchboard production line.