The Kraus & Naimer KG251 is a disconnect switch engineered for reliable isolation of electrical circuits in industrial settings. Rated for 250 A at 690 V nominal, it accommodates both 3-pole and 4-pole configurations and handles motor loads across utilization categories AC-3 and AC-23A. The switch provides forced opening and closing of main contacts, substantial creepage and clearance distances between terminals, and terminal shrouding on models rated 80 A to 250 A for simplified field wiring.
## Technical Specifications
• **Rated Thermal Current:** 250 A (Iu/Ith and Ithe)
• **Rated Uninterrupted Current:** 250 A
• **Nominal Voltage:** 690 V
• **Rated Insulation Voltage:** 600 V AC
• **Rated Impulse Withstand Voltage:** 8 kV (Overvoltage Category III, Pollution Degree 3)
• **Rated Short-Time Withstand Current:** 4600 A for 1 second
• **Maximum Fuse Rating:** 250 A (gG characteristic)
• **Power Loss per Pole:** 8 W
• **Poles:** 3-pole and 4-pole models available
• **Auxiliary Contacts:** Optional 2NO/2NC configurations
## Rated Operational Current
• **AC-20A:** 250 A
• **AC-21A:** 250 A at 20–690 V
• **AC-22A:** 200 A at 220–500 V; 125 A at 660–690 V
## Motor Switching Power (AC-3 / AC-23A)
• **AC-3:** 37 kW to 75 kW depending on voltage and phase configuration
• **AC-23A:** 45 kW to 110 kW depending on voltage and phase configuration
## Key Features
• Forced contact operation for main contacts
• High dimensional clearance enabling straight-line terminal wiring
• Terminal shrouds supplied on 80 A–250 A models
• Screw or ring terminal options with specified torque requirements (16 Nm for M12)
• IP65 enclosure protection on panel-mount variants
## Typical Applications
• Main or maintenance isolation for machine tools
• Distribution panels and switchboards
• Motor load switching and starting circuits
• Mixed resistive and inductive load control
## Compatibility & Integration
Valid for grounded common neutral termination supply systems. Ring cable lug dimensions: 25.00 mm and 34.00 mm terminals. Panel-mount configurations supported.
