Thermal Cutoffs (Thermal Fuses)

Part Number	Description / PDF	Quantity
SC82AAA J.W. Miller / Bourns	TCO 28VDC 25A 82C (180F) SMD	4473
CB72A1B J.W. Miller / Bourns	TCO 28VDC 25A 72C (162F)	2837
CB82A1B J.W. Miller / Bourns	TCO 28VDC 25A 82C (180F)	2385
SC77AAB J.W. Miller / Bourns	TCO 28VDC 25A 77C (171F) SMD	5686
CB77A1B J.W. Miller / Bourns	TCO 28VDC 25A 77C (171F)	2788
SC77AAA J.W. Miller / Bourns	TCO 28VDC 25A 77C (171F) SMD	4573
SC82AAB J.W. Miller / Bourns	TCO 28VDC 25A 82C (180F) SMD	0
SC72AAB J.W. Miller / Bourns	TCO 28VDC 25A 72C (162F) SMD	4897
SC85AAA J.W. Miller / Bourns	TCO 28VDC 25A 85C (185F) SMD	4810
SC85AAB J.W. Miller / Bourns	TCO 28VDC 25A 85C (185F) SMD	0
CB85A1B J.W. Miller / Bourns	TCO 28VDC 25A 85C (185F)	2786
SC72AAA J.W. Miller / Bourns	TCO 28VDC 25A 72C (162F) SMD	4448
CB82ABB J.W. Miller / Bourns	TCO 28VDC 25A 82C (180F)	0
CB85ABB J.W. Miller / Bourns	TCO 28VDC 25A 85C (185F)	0
CB77ABB J.W. Miller / Bourns	TCO 28VDC 25A 77C (171F)	0
CB72ABB J.W. Miller / Bourns	TCO 28VDC 25A 72C (162F)	0

Thermal Cutoffs (Thermal Fuses)

1. Overview

Thermal cutoffs, also known as thermal fuses, are non-resettable overtemperature protection devices designed to interrupt electrical circuits when temperatures exceed predefined thresholds. They act as critical safety components in electrical and electronic systems, preventing overheating-related failures, fires, or equipment damage. These devices are widely used in appliances, industrial machinery, and automotive systems due to their reliability and compliance with international safety standards.

2. Main Types and Functional Classification

Type	Functional Characteristics	Application Examples
Single-shot Thermal Fuses	One-time use; permanently breaks circuit after activation	Household appliances (e.g., hair dryers, coffee makers)
Auto-resetting Thermal Switches	Resets automatically after cooling; limited cycle life	Power tools, battery packs
High-Temperature Cutoffs	Operates above 150 C; ceramic-based construction	Industrial ovens, heating elements
Low-Temperature Cutoffs	Triggers below 100 C; polymer-based materials	Consumer electronics, LED lighting

3. Structure and Components

Typical thermal cutoffs consist of:

Temperature-sensitive element: Bimetallic strip, fusible alloy, or polymer-based material
Contact system: Silver-plated contacts for low resistance
Insulation housing: Flame-retardant thermoplastic or ceramic materials
Termination: Axial leads, radial leads, or surface-mount pads

Advanced designs incorporate hermetically sealed chambers for environmental protection and precise calibration mechanisms for accurate trip temperatures.

4. Key Technical Specifications

Parameter	Importance	Typical Range
Rated Temperature ( C)	Determines activation threshold accuracy	50-300 C 3 C tolerance
Rated Current (A)	Defines maximum operational current capacity	0.1-15A
Response Time (ms)	Time to interrupt circuit after threshold breach	10-500ms
Reset Type	Manual vs. automatic recovery capability	Non-resettable/partial auto-reset
Dielectric Strength (V)	Insulation resistance under overvoltage	1500-5000VAC

5. Application Fields

Consumer Electronics: Smartphones (battery protection), power adapters
Home Appliances: Washing machines (motor protection), rice cookers
Industrial Equipment: Transformers, CNC machine tools
Automotive: Battery management systems, HVAC units

Case Study: In electric kettles, thermal cutoffs prevent boil-dry damage by disconnecting heating elements at 158 C 5 C.

6. Key Manufacturers and Products

Manufacturer	Representative Product	Key Features
Littelfuse	Thermal Cut-Off (TCO) Series	UL/CSA certified, 85-240 C range
TE Connectivity	Klixon 1TS Series	Miniature SMD package, 5A rating
Omron	Thermal Protector KSD Series	Auto-reset function, 10,000 cycle endurance

7. Selection Guidelines

Match rated temperature to system's maximum safe operating temperature
Verify current/voltage ratings exceed circuit requirements
Consider environmental factors (vibration, humidity, thermal cycling)
Select appropriate form factor (through-hole, SMD, panel mount)
Check compliance with safety standards (UL 1434, IEC 60675)

8. Industry Trends

Future developments include:

Nanomaterial-based temperature sensors for faster response times
Integration with IoT-enabled thermal management systems
Miniaturization for wearable electronics (sub-5mm packages)
Eco-friendly designs eliminating cadmium-based alloys
AI-driven predictive thermal cutoff systems