ABB CM-KRN Contact Protection Relay  

1. Key Parameters

• Product Model: CM-KRN (standard identifier for ABB’s contact protection relay series)
• Core Function: Suppresses arcing, inrush currents, and voltage transients on auxiliary contacts of switchgear/circuit breakers; prevents contact wear and oxidation
• Application Compatibility: Auxiliary contacts of MV/HV circuit breakers (e.g., ABB Tmax XT, Ekip series), contactors, and switchgear (rated auxiliary contact current ≤10A)
• Electrical Ratings:
  • Rated Control Voltage (Uₙ): 24V DC / 110V DC / 230V AC (configurable via voltage selector; ±10% tolerance)
  • Maximum Auxiliary Contact Current (Iₘₐₓ): 10A (continuous; 15A peak for 1s)
  • Arc Suppression Capability: Reduces contact arcing by ≥80% (tested at rated voltage/current)
  • Frequency Range (for AC): 50/60Hz
• Protection Features:
  • Transient Voltage Suppression (TVS): Integrated TVS diode (600V clamping voltage) to absorb voltage spikes
  • Current Limiting: Series resistor-capacitor (RC) network to dampen inrush currents during contact closure
  • Reverse Polarity Protection: Prevents damage from incorrect DC voltage wiring
• Mechanical Specifications:
  • Dimensions (W×H×D): 22.5mm × 85mm × 65mm (1-module width, compatible with 35mm DIN rail)
  • Weight: Approximately 80g
  • Mounting Method: 35mm standard DIN rail mounting (EN 60715)
  • Terminal Type: Screw terminals (accepts 0.5mm²~2.5mm² copper conductors)
• Environmental Ratings:
  • Operating Temperature Range: -25℃~+70℃ (-13℉~158℉)
  • Storage Temperature Range: -40℃~+85℃ (-40℉~185℉)
  • Humidity Tolerance: ≤95% RH (non-condensing)
  • Protection Class: IP20 (module body; IP40 when installed in switchgear cabinet)
• Compliance Standards: IEC 61810-1 (auxiliary devices for switchgear), EN 60947-1 (low-voltage switchgear safety), UL 508 (industrial control equipment)

2. Product Features

• Effective Arc Suppression: The integrated RC network and TVS diode work together to suppress electrical arcing during contact opening—preventing contact pitting, oxidation, and premature failure (extends auxiliary contact life by 3~5x in typical applications).
• Wide Voltage Compatibility: Supports multiple rated voltages (24V DC/110V DC/230V AC) via a built-in selector, eliminating the need for separate relay models for different control systems (e.g., industrial DC control vs. commercial AC control).
• Compact 1-Module Design: Slim 22.5mm width fits in high-density DIN rail setups (e.g., LV control panels, switchgear cabinets)—saves space compared to bulky external arc suppressors.
• Reverse Polarity Protection: Prevents damage from accidental DC voltage reversal (a common installation error), reducing replacement costs and downtime during commissioning.
• Easy Installation & Wiring: Clear terminal labeling (power input, contact connection) and tool-less DIN rail mounting simplify setup; no specialized programming required—plug-and-play operation after voltage selection.
• Industrial Durability: Wide temperature tolerance (-25℃~+70℃) and resistance to vibration (IEC 60068-2-6: 10~500Hz, 2g acceleration) ensure reliable performance in harsh environments (e.g., substations, manufacturing plants, mining facilities).
• Seamless Switchgear Integration: Optimized for ABB MV/HV switchgear and circuit breakers (e.g., Ekip UP, Tmax XT)—compatible with standard auxiliary contact wiring, no modifications to existing control circuits needed.

3. Application Fields

• MV/HV Substations: Protects auxiliary contacts of circuit breakers (e.g., 110kV/35kV breakers) and disconnect switches—ensuring reliable operation of control circuits (e.g., tripping, closing signals) in utility substations.
• Industrial Power Distribution: Safeguards auxiliary contacts of contactors and motor starters in manufacturing plants (steel, cement, automotive)—preventing contact failure in motor control centers (MCCs) and reducing production interruptions.
• Renewable Energy Facilities: Used in solar farms and wind parks to protect auxiliary contacts of inverter disconnect switches and grid-connection breakers—supporting continuous energy feed-in to the grid.
• Critical Infrastructure: Protects auxiliary contacts of emergency power switches (e.g., UPS bypass switches, generator transfer switches) in hospitals, data centers, and airports—ensuring fail-safe operation of backup power systems.
• Water & Wastewater Treatment: Shields auxiliary contacts of pump control contactors and valve actuators—preventing downtime in water purification or sewage treatment processes caused by contact failure.
• Commercial Buildings: Integrates into LV switchgear for HVAC control contactors and lighting panel switches—extending the life of switching components in high-cycle applications (e.g., frequent HVAC on/off cycles).

4. Precautions

• Voltage Selection: Set the rated control voltage (24V DC/110V DC/230V AC) correctly via the built-in selector before powering on—incorrect voltage will damage the relay’s internal components (e.g., TVS diode, RC network).
• Current Rating Compliance: Do not use with auxiliary contacts carrying current >10A (continuous) or >15A (peak)—exceeding current limits will overload the RC network and reduce arc suppression effectiveness.
• Wiring Correctness: Follow ABB’s wiring diagram to connect the relay in parallel with the auxiliary contact (not in series)—series wiring will block current flow and disable the contact’s function.
• Polarity for DC Applications: For DC control systems, ensure correct polarity (positive to “+” terminal, negative to “-” terminal)—reverse polarity may trigger the protection circuit but will not damage the relay (reset by correcting wiring).
• Environmental Limits: Avoid installation in condensing humidity (>95% RH) or temperatures beyond -25℃~+70℃; use a climate-controlled cabinet in coastal areas (to prevent salt spray corrosion) or dusty industrial environments.
• Maintenance Checks: Periodically inspect terminal connections for tightness (loose connections cause voltage drops and reduce protection) and verify arc suppression performance via visual inspection of auxiliary contacts (no visible pitting indicates effective protection)