Allen‑Bradley 140M‑I8P‑C50S Motor Protection Circuit Breaker

Overview

Model Code Explanation

• 140M: Bulletin series, motor protection circuit breaker
• I8P: Frame size I8P, compact standard frame
• C50S: Thermal magnetic trip unit code
  • Thermal overload adjustable range: 30–50A
  • Instantaneous short-circuit magnetic trip threshold: 10× rated setting current

Core Electrical Specifications

1. Rated Voltage & Poles
   • 3-pole standard configuration
   • Rated operational voltage: 690V AC 50/60Hz
   • Rated insulation voltage: 1000V
2. Overload Thermal Protection
   • Adjustable thermal dial: 30 A ~ 50 A
   • Class 10 trip characteristic (standard for general industrial motors)
   • Ambient temperature compensated bimetallic thermal element, prevents motor overheating burnout from long‑term overload
3. Short‑Circuit Magnetic Instantaneous Trip
   • Fixed instantaneous trip: 10 × set current
   • Breaking capacity: Up to 100 kA at 480V AC for branch short-circuit fault clearing
4. Mechanical & Auxiliary Options
   • Standard handle: ON/OFF/TRIP visible mechanical indicator
   • Optional auxiliary contact modules (signal trip status to PLC DI module)
   • Optional shunt trip / undervoltage release for remote emergency shutdown
5. Mounting & Environment
   • Mount: 35mm standard DIN rail
   • Housing protection: IP20 terminal area, IP40 front panel
   • Operating temperature: -20°C ~ +60°C
   • Standard screw wiring terminals, compatible with copper cables

Integrated Protection Functions

1. Adjustable thermal overload protection
    
   Match dial setting to motor rated current; delayed trip against continuous overload, avoid motor winding overheat damage.
2. Instantaneous short-circuit magnetic protection
    
   Quick cut off severe short-circuit faults between phases or phase‑ground within milliseconds to protect cables and upstream power distribution.
3. Phase loss / unbalanced load protection
    
   Detects single‑phase loss and severe three‑phase current imbalance, triggers trip to prevent single‑phase motor burnout.
4. Locked rotor stall protection
    
   High inrush stall current triggers fast magnetic trip to protect motor during startup jamming.
5. Clear fault indication
    
   Handle locks in TRIP position after fault; manual reset required to restore power, convenient for maintenance fault identification.

Matching Supporting Equipment

1. Motor control components
    
   A‑B 100‑series AC contactors, thermal overload relays, motor starters
2. PLC & signal feedback
    
   SLC 500 (1747‑L532) + 1746 digital input modules; auxiliary contact feeds breaker trip signal to PLC for HMI alarm
3. Safety & power accessories
    
   440R safety relay, 24V DC power supply, Stratix managed switch (1783‑MMX14T2S) for centralized motor monitoring network

Typical Industrial Applications

• Water treatment pump & fan motor control cabinets
• Packaging, conveyor, material handling motor starter panels
• Petrochemical auxiliary small and medium motor branch protection
• HVAC air blower, cooling tower motor control circuits
• Factory assembly line machine tool motor protection