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- PCB-monterad säkringshållare 27
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- termostat 49
- Elektrisk säkring 23
- Biltemperatursensor 7
- Termisk effektbrytare 20
- Säkringsboxhållare 36
- Temperatursensor 75
- Termobrytare 68
- Bilsäkring 19
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- Termisk säkring 32
- ytmonterade säkringar 12
- termistor 27
Produkttaggar
Tillämpning och val av krafttermistorer
Vad är en krafttermistor? En krafttermistor, Även känd som en Power NTC eller inrush -strömbegränsare, är en komponent som är utformad för att undertrycka Inrush -strömmar i elektriska kretsar. Den använder det självvärmande kännetecknet för en negativ temperaturkoefficient (NTC) termistor för att begränsa de höga strömmarna som kan växa när en krets är påslagen.
Power thermistor (mainly negative temperature coefficient NTC type) is a key component for suppressing surge current in electronic circuits. Its main parameters, selection points and application scenarios are as follows:
jag. Core functions and principles
Surge current suppression
At the moment of power startup, the NTC resistance value connected in series in the input circuit is high, which can limit the peak current; after power is turned on, the resistance drops rapidly due to heat (power consumption can be ignored), ensuring the stable operation of subsequent circuits.
Negative temperature characteristics
The resistance value decreases exponentially with increasing temperature: R(T)=R0⋅eB⋅(1T−1T0)R(T)=R0⋅eB⋅(T1−T01) (R0R0 is the resistance value at 25℃, BB is the material constant).
How it Works:
High Initial Resistance:
When power is first applied, a power thermistor has a high resistance, which limits the initial inrush current.
Self-Heating:
As the current flows through the thermistor, it generates heat, causing its resistance to decrease.
Resistance Decrease:
The reduction in resistance allows the circuit to draw the necessary operating current without the initial surge.
Benefits:
Protects Equipment:
By limiting the inrush current, power thermostats prevent damage to sensitive components and equipment.
Reduces Power Loss:
The resistance decrease through self-heating reduces power loss compared to using a fixed resistor.
Energy Savings:
Lowering power loss can lead to energy savings in applications like switching power supplies and other electrical devices.
Ii. Key parameters and selection points
Parametrar | Definition and selection significance | Typical value/range |
Rated zero power resistance (R25) | The nominal resistance at 5°C determines the initial surge suppression capability. Calculation formula: R25≈U2⋅IsurgeR25≈2⋅IsurgeU (UU is the input voltage, IsurgeIsurge is the surge current) | Commonly used 2.5Ω, 5Åh, 10Ω±(15-30)% |
Maximum steady-state current | The current that can be sustained for a long time at 25℃, needs to be greater than the circuit working current | Depending on the model 0.5A~tens of amperes |
Residual resistance | The minimum resistance value at high temperature (such as 100℃), affecting the normal power consumption of the circuit | About 1/10~1/20 of R25 |
B -värde | Material constant (measured at 25℃~50℃), determines the slope of the resistance-temperature curve; high B value responds quickly but has high cost | 2000K~6000K |
Termisk tidskonstant | Response speed index, patch type (such as SMD) can reach seconds | Glass seal/enameled wire type about 10~60 seconds |
Note: Example of model identification MF72-10D-9:
10: R25=10Ω.
D: Disc package
9: 9mm diameter;
III. Typical application scenarios
Power supply equipment: Input surge suppression of switching power supply, UPS, adapter;
Lighting system: Anti-shock protection of LED driver, ballast, lighting distribution box;
Industrial equipment: Motor start, industrial power supply, medical instrument;
Household appliances: Air conditioner, refrigerator compressor start protection;
Iv. Selection and avoidance guide
Current matching
The maximum steady-state current needs to be greater than 1.5 times the actual working current to avoid continuous heating and failure.
Heat dissipation design
In high-power scenarios, sufficient spacing or auxiliary heat dissipation is required to prevent excessive temperature rise from causing insufficient residual resistance.
Extreme temperature
The operating temperature range is generally -55℃~+125℃. Glass-sealed models (resistant to 150℃) are preferred in high-temperature environments.
V. Package and performance comparison
Package type |
Advantages | Applicable scenarios |
Epoxy resin | Low cost, good waterproofness | Home appliances, ordinary power supplies |
Glass package | Hög temperaturmotstånd (>150℃), snabb respons | Industrial equipment, automotive electronics |
Surface mount type (SMD) | Liten storlek, suitable for high-density PCB | Compact power module |
Tip: Be cautious in frequent switching scenarios – NTC may lose surge suppression capability when insufficient cooling is insufficient. Just nu, a parallel relay bypass can be connected.
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