行业组件数据 · 2026

热脱扣单元

A thermal trip unit is a protective device in circuit breakers that detects overload currents using a bimetallic strip, triggering disconnection to prevent equipment damage and fire hazards.

技术定义与适配语境
典型 热脱扣单元 会按材料、尺寸公差、适配关系和失效风险在 电气设备制造 中评估。

The thermal trip unit is an essential component within circuit breakers and main disconnect switches, designed to provide overload protection by responding to sustained excessive currents. It operates based on the thermal effect of current flow, where a calibrated bimetallic strip heats and bends when current exceeds the rated threshold for a predetermined time. This mechanical action releases the trip mechanism, opening the contacts to interrupt the circuit. Unlike magnetic trip units that respond to short circuits, thermal units protect against gradual overloads that could cause insulation degradation, overheating, or fire. They are characterized by an inverse time-current curve, meaning trip time decreases as overload severity increases. Modern versions may integrate with electronic trip units for enhanced coordination and monitoring.

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组件规格

定义
The thermal trip unit is an essential component within circuit breakers and main disconnect switches, designed to provide overload protection by responding to sustained excessive currents. It operates based on the thermal effect of current flow, where a calibrated bimetallic strip heats and bends when current exceeds the rated threshold for a predetermined time. This mechanical action releases the trip mechanism, opening the contacts to interrupt the circuit. Unlike magnetic trip units that respond to short circuits, thermal units protect against gradual overloads that could cause insulation degradation, overheating, or fire. They are characterized by an inverse time-current curve, meaning trip time decreases as overload severity increases. Modern versions may integrate with electronic trip units for enhanced coordination and monitoring.
工作原理
The thermal trip unit operates on the principle of thermal expansion. A bimetallic strip, composed of two metals with different coefficients of thermal expansion, is heated by the load current passing through it. Under normal conditions, the strip remains straight. During an overload, the increased current generates excess heat, causing the strip to bend due to unequal expansion of the metals. This bending actuates a latch or lever mechanism, which releases the spring-loaded contacts to open the circuit. The trip time depends on the magnitude of the overload, following an inverse-time characteristic: higher currents cause faster tripping. The unit resets automatically after cooling or via manual intervention, depending on the design.
材料
Bimetallic strip (typically nickel-iron or copper-steel alloys)insulating housing (thermoset plastics like phenolic or polyester)contact materials (silver alloy or copper-tungsten)springs (stainless steel or phosphor bronze)and calibration screws (brass or steel).
Trip Class
10, 20, 30 (e.g., Class 10 for motors)
Mounting Type
Fixed or plug-in
Rated Current
10A to 6300A
Mechanical Endurance
>10,000 operations
Calibration Tolerance
±10% to ±20%
Operating Temperature Range
-20°C to +70°C
标准
ISO 8820DIN EN 60947-2IEC 60947-2

行业分类与别名

热脱扣单元 的常用贸易名称、技术标识和检索关键词。

thermal trip unitcircuit breaker overload protectionbimetallic stripelectrical protection devicethermal-magnetic breakerIEC 60947-2trip class热脱扣单元Thermal Trip Unit电气设备制造 热脱扣单元

上级产品

该组件会出现在以下整机或工业产品中。

断路器/主隔离开关
一种安全装置，可在电路发生过载或短路时自动切断电流，并提供手动隔离能力。
查看产品详情 ->

FMEA · 风险与缓解

诱因 → 失效模式 → 工程缓解

Bimetallic strip contamination or corrosion->Reduced sensitivity, delayed or no trip->Use sealed housings, regular inspection, and replace per maintenance schedule
Mechanical wear in trip mechanism->Inconsistent tripping or failure to reset->Design with durable materials, lubricate moving parts, and conduct operational tests
Overheating from high ambient temperatures->Premature tripping below rated current->Select units with temperature compensation, ensure proper ventilation, and derate as needed

工业生态与工程逻辑

兼容对象
Low Voltage Circuit BreakersMolded Case Circuit Breakers (MCCBs)Main Disconnect SwitchesMotor Protection Circuit Breakers
可替换件
Schneider ElectricABBSiemensEatonLegrand
0
Failure to trip during overload leading to fire
1
Nuisance tripping from ambient temperature changes
2
Calibration drift over time
3
Material fatigue in bimetallic strip after repeated cycles

合规与检测

tolerance
Trip current tolerance typically ±10% at reference temperature (e.g., 30°C), with time delays per trip class (e.g., Class 10 trips within 10 seconds at 600% current).
test method
Testing per IEC 60947-2: apply specified overload currents (e.g., 1.05 to 1.3 times rated current) and measure trip times; verify inverse-time characteristics and calibration stability across temperature ranges.

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采购评估维度

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技术文档
4/5
制造能力
4/5
可检验性
5/5
供应商透明度
3/5

这些分值是采购评估维度示例，不代表真实客户评分、具体国家买家反馈或实时询盘。

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阳极/阴极端子
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灭弧室/隔弧板
Critical safety component in circuit breakers and fuse holders that contains and extinguishes electrical arcs during interruption.
灭弧栅片
Arc chute plates are insulating plates in circuit breakers that split and cool electrical arcs during interruption to ensure safe current interruption.

常见问题

What is the difference between thermal and magnetic trip units?

Thermal trip units protect against overloads by responding to heat from sustained excessive currents, with an inverse time delay. Magnetic trip units protect against short circuits by responding to sudden high currents, tripping instantaneously. Many circuit breakers combine both in thermal-magnetic designs.

How do you calibrate a thermal trip unit?

Calibration involves adjusting the bimetallic strip tension or position using screws, based on testing at specific current levels and durations per standards like IEC 60947-2. It ensures the unit trips within the specified time-current curve. Factory calibration is typical; field adjustments require specialized tools.

Can thermal trip units be used in DC circuits?

Yes, but performance may vary. Thermal units rely on current-induced heating, which works for both AC and DC. However, calibration and trip characteristics might differ due to DC's constant current flow, so use models rated for DC applications.

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CNFX Industrial Component Index · 电气设备制造

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URN:CNFX:ME:UNIT:THERMAL_TRIP_UNIT