α ααα»α’αααΈααΆαααΆαα·αααααααΆαα αααΎααααα ααα‘αα§αααααααΆαααΆα α αΎαααααΌαα αααΆαααααΆαα
ααΆαααΈαααα»α αα·ααααααααααααααααααααααα·ααααααΆααααα½ααααΌαα»ααα·ααααα PLC ααααααΆαααααΆααΎαααΈααΈαααα»αααααααααααΆααα½αααα ααΌαα ααα»? ααααααΈαααΌα freewheeling αα ααΎα§ααααααααααΌααα αααααα 850 αα»ααααΆααααααΆααααααΏααααααΆαα ααΌαααΉα 12 ααααααααΆαααα’αΆαααααΎαααΆαα α’αααΈααααα½αα±ααα’ααααααΎα αααααΊααΆ ααΈααΆαααααααΎαααααΆαααα‘αΎαα§αααααααΆαααΆαααΆαααΎαα‘αΎαααααα 15,000 αα»ααααΆα ααΎααααΈααΆαααΆααααααΆααααΉαααΆααααααααΆααα.
ααααΆααΈαααΌααααααα αΆαααΈααΆααααα ααα‘αααααααΆαααα½αα ααΈαααΌα freewheeling αα·αα§ααααααααααααΆααααΆαααΎαα‘αΎααα·ααααααΆαααααΎααααα½αααααΆαα αα½αααΆααΆαααΆααααααΆααααΉαααΆαααααΆαααα αααα»αααααΆααΆαααααα»ααα ααααα·ααα»αααααΆααΆαααααα»αα. ααΆααααα ααα‘ααα½αααΆ α¬αααααααΆα§ααααααα½ααααα½αα§ααααααααααααα αα»αα ααααααααα αααα αααα»ααα»αααααΆαααααααΆαααΆαααααα’ααα ααααα ααΈαααα»ααααααΆαα±ααααΆαααΆααααΆααααααααΆααααααααααα.
ααααα»αααααααααααααααααΌαααΆαα αααΆααααΆααααααααα αα ααααα ααΎααααΈαααααΆααα§αααααααΆαααΆαααααΉαααααΌααααααΆαααααααααααΆαααΆα αα»αααααΆααααα α»ααααααααααΆαααααααααα αα·ααααααΈααΌαα ααα»ααααααααααααααααΆααα ααΆαααΆαααααΉαααααΌααααααΌαα±αααα αα αααα·ααααΆααΆααααΈαααααΎαααΆαααΆαα½αααααΆα.
ααααααααα’αααΈααΈαααΌα Freewheeling (ααΈαααΌα Flyback/Snubber)
ααΎααΈαααΌα Freewheeling ααΆα’αααΈ?
ααΈαααΌα freewheeling αααααααΌαααΆαααα α αααααααΆ ααΈαααΌα flyback, snubber, suppressor, catch, clamp α¬ commutating ααΊααΆα§ααααα semiconductor αααααααΆααααααααΆααααααα»α inductive ααΎααααΈαααααααΆααααΆαααΎαα‘αΎαααα»ααααααΆααααααΎαααα‘α»ααααααααΌαα αααααααα ααααα ααΆαααΆααα»αααΆαα (ααααααααΈααααα, MOSFETs, IGBTs, ααααΆαααααααααααΌαα, αα·ααααα PLC) ααΈ back-EMF (αααααΆααα’αα‘α·α ααααΌαααΌααα) ααααααααα·α ααααααΆααααααα·ααα ααααααα ααααααααααΆαα inductor ααααΆααααααΌαααααΆααα.
αααα αΆααΎαα‘αΎαααα»αα αα ααααααα ααααααααααΆαα inductor (α§ααααααααααΌαα, solenoid, ααα»ααααΌααα) ααααΌαααΆαααααΆα α αααΆαααααα Lenz α ααααΆααααααΆαααα·ααα½αααα αα·ααααααΆαα±ααααΆαααΆαααΎαα‘αΎαααα»ααααααααΆααΆααααααΆααα αΌαα ααααα ααΆαααΎαα‘αΎααααααααΎααΆααααΈααΆα V = -L(di/dt) ααα L ααΊααΆ inductance α αΎα di/dt ααααΆαα±ααα’ααααΆααααΆαααααΆααααααΌαα ααααα ααΆαα½αααΉαααααΏαααααΌαααααααΆ ααα»ααααα’αΆα ααΆαααα 10Γ ααα»ααααααααααα α¬αααααααΆαααα αααααααααααΆαααααααΈ 24V αα ααΆαααααααααΆαα 300V+ αααααααααΆααα»αααΆαα semiconductor ααααΆααα.

αααααααααΈαααΌα Freewheeling ααααΎαααΆα
ααΈαααΌα freewheeling ααααΆαααα αααα»α ααααααΆαα½αααΉαααααα»α inductive αααα αααΆααααΌααα ααΆααααααααααα. α ααΆαααΆααααΆααααααααααααΎαααααααΆαααΆαααΆαα
ααα‘α»ααααααααα·ααααα·ααΆαααααααΆα ααΈαααΌαααααΌαααΆααααα αααΆα (anode α’αα·αααααΆαααΆα cathode) ααΌα ααααααΆαααα αΆαααΈ impedance ααααα α αΎααα·αααααΎα ααααααα α ααααα αΌαααΆααααααΆααααααΆααααααα»α inductive ααΈααΆαααααααααααααΆαααααα»αααΆαααα·αα.
αα αααααααα»αααΆααααΎαα Inductor ααααΆααΆααααααΆααα αΌαα αααα ααα»ααααααΆαα½αααΉααα»αααΆααααΎα αα·αααΆαααααΌαααααααΆααααΆαααααααααααααα αααΌαααα»α inductor αααα αααΆα (α α»αααααα·αααααΆαααααΆαααΆα’αα·αααααΆα) ααααααααΌαααααααΈαααΌα freewheeling α ααΈαααΌαα αΆααααααΎαααααΎα ααααααααΆαα ααααααααααΌαααααα·ααα»ααα·αα inductor β diode β αααα‘αααα inductor αα·αα.
ααΆαααααΆααααΆαααα ααΆααααααΆαααα·αααααααα»ααα αααα»α inductor (E = Β½LIΒ²) ααααΆααααΆαααα αα αααα»αααΆαααα DC αααα inductor αα·αααΆαααααΆααα α»ααα αα»ααααα diode α α ααααααα α»αααΆααααΆααααΆαα½αααΉαααααααααααΆ Ο = L/R ααα R ααΊααΆααΆααααααααααα·ααα»αααα»αα ααα»αααααααΆαααα»αααΆααααααΌαααΆαααααααα αα ααα»ααααααααααα + ααΆαααααΆααα α»ααα αα»ααααα diode (0.7-1.5V)βαα»ααααα·ααΆααααααΆαααα»αααΆαααααααααΆαααΆααα’ααα.
αααααααα αα ααααα
- αααααααΆααααΎαααα Nanoseconds (ααΆααααααΆ <50ns for standard silicon, <10ns for Schottky)
- ααΆααααααααααααα»αα ααΆααααααΆ <100V DC circuits (though PIV ratings can be 400V-1000V)
- ααΆαααααααααααα αα α»ααααααα ααΆαααΆααααααααΆαααααααααΆααααΈ 1A αα 50A+; ααΆαααΆααααααααΎαα‘αΎαααααααα’αΆαααα 20A-200A (αααααΆαααααααΆαααααααΆααααΈαα»α 8.3ms)
- ααΆαααααΆααα α»αααα»ααα αα»αα 0.7-1.5V (ααααααααααΈααΈαα»α PN), 0.15-0.45V (αααΆαα Schottky)
- ααααααααΌαα
α
- αααΈααΈαα»ααααααααΆα (αααααΈ 1N4001-1N4007)α αααααααααΌαα ααΆαααΆαααααα PIV 50V-1000V, 1A αααα
- ααΈαααΌα Schottkyα ααΆαααααααααααΏα (<10ns), low forward drop (0.2V), preferred for PWM circuits >10kHz
- ααΈαααΌαααααααααααΏαα ααααΎα±αααααααΎαα‘αΎααααααΆαααααααα·ααΈααααΌαααΉα αααααααΆαααααααα <100ns
αααααα·ααΈααααααΆα α§ααααααααααΆα§ααααααααααΌαα ααΆααααααααααααααα solenoid αααΌααα DC PWM ααααΆα α§αααααα αΆαααααααα₯ααααααααααα ααααααΈ contactor α§ααααααααααΆ HVAC αααΌαα»α Arduino/microcontroller I/O α.
αααααααα·αα·α ααααααααΎαααΎα
- αααααααΆαα αααααα αα»αααααΌαα ααααΌααααααααααΆαααΆααααα ααααΆαααααααααα»ααααα inductor α ααααΆα ααααααααααα’αΆααααααααΌααααα αα I_peak β V_supply / R_coil αααααΆααααααααΎαααΎα diode αααααααΌαααΆαααΆαααααααααααΆαα 2-3Γ αααααααα ααΎααααΈαααααααΉααα»ααααα·ααΆαα.
- ααα»αααααααααα αααΆα (PIV)α ααααΌαααααΎαααΈααα»αα’αα·ααααΆαααα’αΆα ααα α‘αΎαααααααΆαα diode α ααΆαα’αα»αααααααα’αα·ααααα PIV β₯ 10Γ ααα»αααααααααααα αααααΆααααααααΈ 24V ααααΎ diode αααααΆαααΆαααΆαααααα β₯400V (1N4004 α¬αααααααΆαααα)α.
- ααΆαααααΆααα α»αααα»ααα αα»αα ααΆααααααΆαααΆααααααα’ ααΎααααΈααΆαααααααααΆαααααΆααααΆαααααα‘α»αααα freewheeling α ααΈαααΌα Schottky (Vf β 0.2V) ααααΆααααΆααα 1/3 αααααΈααΈαα»ααααααααΆα (Vf β 0.7V) αααααΆααα ααααααααΌαα.
- αααααααΆααααααααα αααααΆααααΆαααααΌααααααααααααα (PWM >10kHz) ααααΎααΈαααΌα Schottky α¬ααΈαααΌαααααααααααΏαα ααΈαααΌα rectifier αααααααΆαα’αΆα ααΆααααααααΆαααααααα >1ΞΌs ααααααααΆαα±ααααΆαααααααΆαααααΌααα αααα»αααααααΈααΏαα.
ααααααααα’αααΈα§ααααααααααααΆααααΆαααΎαα‘αΎα (SPD/MOV/GDT)
ααΎα§ααααααααααααΆααααΆαααΎαα‘αΎαααΊααΆα’αααΈ?
α§ααααααααααααΆααααΆαααΎαα‘αΎα αααααααΌαααΆαααα α ααΆααααΌαααΆαααΆ α§αααααααΆαααΆαααΆαααΎαα‘αΎα (SPD) α¬α§ααααααααααααΆααααΆαααΎαα‘αΎαααα»αααααααα’αΆαααα (TVSS) ααΆαααΆαααααααααα’αααα·αααΈααΆααααΌαααΈααΆαααΎαα‘αΎαααΆααααααααααΆααααα α αα·αααΌα ααΆαααΆαααΆαααααα·ααααΆαααΆαα»ααααΈαααΌα freewheeling α§ααααααααααααΆααααΆαααΎαα‘αΎαααΆαααΆααααααΆααααΉα ααΆαααααΆαααα ααααααα·ααααααααα αααα αΌαααΆααααααααα ααα αΆαααΆαααα.
αααααα ααααααααΆαααΎαα‘αΎαααΆααααα α
- αααααααΆααα ααΆααααααααΆαααα ααΉαααααααΆαααΎ α¬ααΆααααααΈαα αααααααααααααααΆαααα αααα»αααααααααΎα (α αααααααα»α 20kA-200kA)
- ααααα·ααααα·ααΆαααααΌααααααΆαα ααΆαααααΌααααΆααΆα capacitor α§αααααααααΎααααΆαα ααΆααααααααΆαααααα transformer ααΆααααα’αΆαααα α»α (ααααααα’αΆαααα 2kV-6kV)
- ααΆαα αΆααααααΎααααΌαααα α αααα inrush αααΌααααααααααΎαα±ααααΆαααΆαααααΆααα α»αααα»α αα·αααΆαααΎαα‘αΎααα·αααααααα’αΆαααα
- ααααα·ααααα·ααΆααααΆααΆα Capacitorα ααΆαααααΌα capacitors αααααααΌααααααΆααΆααααααααΎαα±ααααΆαααΆαααΎαα‘αΎααααααααααααα
αααααααα§ααααααααααααΆααααΆαααΎαα‘αΎαααααΎαααΆα
α§ααααααααααααΆααααΆαααΎαα‘αΎαααααΎαααΆαααΆαα»αααααα»ααααααααΆααααααΌαααΈ impedance ααααααα impedance ααΆα αα ααααααααα»αααΎαααΈααααα·αααααα αααααΎαααααΌααα ααΈαααααααααα ααααααΎαα‘αΎαα ααααΈα§ααααααααααΆαααΆαααΆαα.
ααααααΆα Metal Oxide Varistor (MOV): MOV ααααβα‘αΎαβααΈβαααααΆαα·α βα’α»ααααΈαβαααααααΈβαααβααααααβα αΌαβαα βαααα»αβααΈα α¬βαααα»αβαααΆαβα’αα‘α·α ααααΌαβααα αβααΈαα αα βααα»αβααααα·ααααα·ααΆαβααααααΆ MOV αααα αΆαβααΆαβαααβααααΆαβαααααβαααα»α (>1MΞ©) α αΎαβααΆαβααβα ααααβααα βααααΆαβααΈααααΌα’ααααβααα»αααααα αα ααααααααα»αααΎαα‘αΎααααααα»α varistor (Vn) αααααααααααΆααααααααΆαα·αααΆαααααΈααααΆαα ZnO αααααααΆααααααααΆααα α»αααα <1Ξ©, and the MOV conducts surge current to ground. After the transient passes, the MOV automatically returns to high-impedance state.
ααααααΆα Gas Discharge Tube (GDT): GDT ααΆαα’αα‘α·α ααααΌαααΈα α¬ααΈααααααααααααααααΆαααΌα α (<0.1mm) inside a sealed ceramic or glass tube filled with inert gas (argon, neon, or mixtures). At normal voltage, the gas is non-conductive and the GDT presents open-circuit impedance. When applied voltage reaches the spark-over voltage (Vs), the gas ionizes (creating a plasma), impedance drops dramatically, and the GDT conducts surge current through the ionized gas path. After current falls below the holding current threshold, the gas de-ionizes and the GDT returns to its insulating state.
ααα»αααα: ααα»αβαααβααα βα‘αΎαβαα βααΌααΆααβα§αααααβαααβααΆαβααΆαααΆαβα’αα‘α»αβαααβααΆαβααΆαβααΎαβα‘αΎαβααααΌαβααΆαβααβα α βααΆ βααα»αβα’αα»ααααΆαβα±ααβααααβααΆααβ α¬ βααΆαβααΆαβαααααβααΆαβααΆαααΆαβααα»αβ (Vr)α ααααα Vr ααΆαααΆααααααααΌαααΆαααΆαααΆαααΆαααααααααΎαα SPDs ααααΌαααΆαααααααααααααααααα»αααααα½αααααααα ααααα·αα ααααααΎαα‘αΎαααΆααααΆαα (ααΆααααααΆααααΌαααΆαααΆααααααα 5kA α¬ 10kA, ααα 8/20ΞΌs)α.
αααααααα αα ααααα
- αααααααΆααααΎαααα
- MOV: <25 nanoseconds (component level). α αααΆαα ααααααααααααΆαααΆαα»ααααΎαααααααΆαα ααααααααααααα‘αΎαααααααα’αΆαααα»α αααα»αααααααααΆαααααΆαααααΆααααααααααααΆααααΎααααααααααααααα αα·αααα»αα’αα»ααααΆαα±ααααααααΆααα ααΆαααα‘αΎαααΆααααααΆαααααΉαααααΌαααΊααΆαααΆααααααΆααα.
- GDT: 100 nanoseconds αα 1 microsecond (ααΊαααΆααααααΆαααΆααααααΆααα ionization α§ααααα)
- Hybrid (MOV+GDT): <25ns initial response (MOV), sustained conduction via GDT
- ααΆααααααααααααα»αα αααααααα 120V AC αα 1000V DC (ααα»αααααα·ααααα·ααΆααααα Un)
- ααΆαααααααααααα αα α»ααααααα α αααααααα ααααααα»ααααααΆααααααα (In) 5kA-20kA, α αααααααα ααααααα»αα’αα·ααααΆ (Imax) 20kA-100kA (ααα 8/20ΞΌs αααα»ααα½α IEC 61643-11)
- ααΆαααααΌαααααΆααα: MOVs ααααΌαααΆαααΆααααααααΆ joules (J); SPDs αααααααααααΆ: 200J-1000J αααα»ααα½αααααΆααααΆα
- α
αααΆααααααΆαα (UL 1449 / IEC 61643-11):
- αααααα 1 (ααααΆαα I): α αααα αΌαααααΆαααα, ααΆαααααααΆαα½αααα 10/350ΞΌs (αααααααααΎααααααααααααααααααΆαα), ααΆαααΆαααααα 25kA-100kA
- αααααα 2 (ααααΆαα II): αααααα ααα αΆα, ααΆαααααααΆαα½αααα 8/20ΞΌs (αααααααααααααααααααα/ααΆαααααΆααααααΌα), ααΆαααΆαααααα 5kA-40kA
- αααααα 3 (ααααΆαα III): α ααα»α ααααΆαααααΎααααΆαααα αα·αααααα»ααααααΆαααααααα, ααΆαααΆαααααα 3kA-10kA
- ααΆαα’αα»αααααΆααααααααΆαα UL 1449 Ed.4 (α’αΆαααα·αααΆαααΎα), IEC 61643-11 (α’ααααααΆαα·), IEEE C62.41 (ααΆααααααααααααααα·ααααΆαααΎαα‘αΎα)
ααΆααααααααααα αα αααα·ααααΆ MOV vs GDT
| αααααα | αααα’α»α Varistor(αααΌα) | α§ααααααααααααα(α’ααα) | Hybrid (MOV+GDT) |
|---|---|---|---|
| ααααΎααααααααααΆ | <25ns (very fast) | 100ns-1ΞΌs (ααΊαααΆα) | <25ns (MOV dominates initial response) |
| ααΆααααααα»α | ααααα (1.5-2.5Γ Un) | ααΆα (1.3-1.8Γ Un) αααααΆααααΈ ionization | ααΆαααα»ααααααΆααααααααΆααααααααααα½α |
| αααααααΆααα αα α»αααααα | ααααα (20kA-100kA αααααΆααααΈαα αααααΈ) | αααααααΆαα (40kA-100kA αααα) | ααααααααα»α (MOV αααααααΆααααααΏα GDT αααααααΆαααΆααα) |
| ααΆαααααΌαααααΆααα | αααααααααααΆαααααα , ααα·αααααααΆααΎααααααααΆ | ααα’α₯αααα αα, ααααΎαααααααΆααααααααααααααΆααα αααααααααΆαααΆαααααα | ααα’α₯αααα αα, MOV ααααΌαααΆαααΆαααΆαααα GDT |
| α ααααααα ααααΆα | 10-100ΞΌA (ααΎαα‘αΎαααΆαα’αΆαα») | <1pA (essentially zero) | <10ΞΌA (GDT isolates MOV at normal voltage) |
| αααααααΆα | ααααα (500pF-5000pF) | ααΆαααΆαα (<2pF) | ααΆα (GDT ααΆαααααΈααΆααααααααααααααΆααααααΆαααααα·αααααΆα) |
| αααααααΆααα | α’αΆα ααααΈ α¬ααΎα; αααααΌαα±ααααΆαααΆαααααΆα αααααα | ααΆααααααΆααααΈ (ααα»αααααΆααααΎαααα α»α) | ααΆαααααΆα αααααα MOV ααΆαααΆααααααααααΆααααααΎα |
| α’αΆαα»ααΆα | ααα·αααααααΆααΆαα½αααΉαα ααα½αααΎαα‘αΎα αα·αααΆαααΆαααΉαααΎαααα»α | ααααΎαααααααΆααααααααα (ααΆαααααααααααΆααααααα·ααααα·ααΆα 1000+) | αααααΈα (GDT ααΆαααααααααΆαααΆαααΉα MOV) |
| ααΆαα αααΆα | ααΆα ($5-$20) | ααααα ($10-$30) | αααααααΆα ($25-$75) |
| αααααα·ααΈααα’αααα»α | ααααααΈ AC/DC ααΌαα , ααΆααααααΎαα‘αΎααα·α, αααααα§ααααΆα αααα | ααΌαααααΆαααα, αααααα·αααααα, α§αααααααΆαααΆααααΆαα (αααααααΆαααΆαααααΆαα) | αααααα·ααΈααααΆααααααααααΌαααΆαααΆαααΆαααΆα αα·αα’αΆαα»ααΆαααααΎααααΆααααΆαααΌα |
ααΆαααααααααα αα ααααααΆ: Freewheeling Diode vs Surge Arrester

| αααααα | Freewheeling Diode | α§αααααα αΆααααα (SPD) |
|---|---|---|
| αααααααα αααα | αααααααΆααααΆαααΆααααααααα inductive ααΈααααα»ααααα»ααααα»α | ααΆαααΆαααααααααααΈααΆαααΎαα‘αΎαααΆααααααααααΆααααα |
| αααααααΎαααΎαα‘αΎα | ααααα‘αΎαααααααα½αα―α (ααααα»α inductive ααααααααααΈααααΆαα) | ααΆααααα (ααααααααααα, ααΆαααααΆααααααΌααααααΆα) |
| ααΆαααααααΆαααΆαααΆα | ααααα·ααααΆαααΆαα» (αα»αααΆαα/ααααααααΈααααααααα½α) | ααααα·ααααααααα (αααααα’αααα·αααΈααΆααααΌα) |
| αα½αααα»α | <100V typically | ααΆαααααα ααΆααααΆααααα»α |
| αααααααΆααα αα α»αααααα | α’αααα (ααααααα’αΆαααα: 20A-200A) | ααΈα‘αΌα’αααα (5kA-40kA+) |
| ααααΎααααααααααΆ | ααΆααΌαα·ααΆααΈ (Nanoseconds)<50ns) | ααΆααΌαα·ααΆααΈ (MOV) αα ααΈααααΌαα·ααΆααΈ (GDT) (Nanoseconds (MOV) to microseconds (GDT)) |
| αα αα αααα·ααααΆ | α ααα»α ααααααα PN ααΆαααα α¬ ααΈαααΌα Schottky (Simple PN junction or Schottky diode) | MOV, GDT, α¬αααΆαααΆαα»αααααααααΆαα·α ααΌαααΆαα (MOV, GDT, or hybrid ceramic-based components) |
| ααΆααααααααααααΆααα | ααΈααΈααΌα αα ααΌα (Millijoules to joules) | ααΆαααα αα ααΆααααΆαα ααΌα (Hundreds to thousands of joules) |
| ααΆααααααΆαα | ααααααααΆααααααΆααααααα»αα’αΆαααα»α ααα (Parallel across inductive load) | ααααααααΆααααααΆααααααααΆααα (ααΈαααααα ααΈ, ααΈαααααα αααα) (Parallel across power lines (line-to-ground, line-to-line)) |
| ααΆαααααααα»αααΆα (Degradation) | ααααα·ααα·α αα½α αααα»α (ααΎααααααααΎαααΈααααα·α PIV) (Minimal (unless exceeded PIV rating)) | MOV ααααααα»αααΆαααΆαα½αααΉαααΆαααΎαα‘αΎαααααα αΎαααααααα; GDT α’αΆαα»ααΆαααα (MOV degrades with repeated surges; GDT long-life) |
| ααΆαα αααΆα | $0.05-$2 αααα»ααα½ααααΆαααΆα ($0.05-$2 per component) | $15-$200+ αααα»ααα½αα§ααααα SPD ($15-$200+ per SPD device) |
| αααααααΆα | ααααααααΌαα ααααΈαααΌα (JEDEC, MIL-STD) (General diode specs (JEDEC, MIL-STD)) | UL 1449, IEC 61643, IEEE C62.41 |
| αααααα·ααΈααααααΆα | α§ααααααααααΆ Relay, α§ααααααααααΆαααΌααα, Solenoids (Relay drivers, motor controls, solenoids) | α αααααααΆαααα, αααααα ααα αΆα, α§ααααααααααΆαααααααα (Service entrances, distribution panels, sensitive equipment) |
| ααΈααΆααααα‘αΎα | αααααααΆαααα ααααΆααΈαααααα»αα’αΆαααα»α ααα (Directly at inductive load terminals) | ααααΆαααααα, αααααα ααα αΆα, ααααααα (Main service, distribution panels, sub-panels) |
| αααα·ααΆαααααΆααααΆααα (Failure Consequences) | ααΌα ααΆααα»αααΆαα/αα·ααααα PLC ($50-$500) (Damaged switch/PLC output ($50-$500)) | ααααααΆαα§ααααα/ααααααααααΆααααΌα ($1000s-$100,000s) (Destroyed equipment/entire system ($1000s-$100,000s)) |
| ααα·ααΆααααααααΌαααΆα (Required Quantity) | αα½ααααα»ααα½αααααα»αα’αΆαααα»α ααα (α’αΆα ααΆα 100 αααα»ααα½ααααααα) (One per inductive load (could be 100s per facility)) | 3-12 αααα»ααα½ααααααα (Cascade αααααΆααααααααααα½α) (3-12 per facility (coordinated cascade)) |
αααααΆααααΌαααααΎα§αααααααΆαααΆαααΈαα½αα (When to Use Each Protection Device)
αααααα·ααΈααΈαααΌα Freewheeling (Freewheeling Diode Applications)
ααααΆααΈαααΌααΆαααΆαααααα·ααααΆαααΆα: (Component-level protection scenarios:)
- αααΌαα»ααα·ααααα PLC: (PLC output modules:) αα ααααα·α /αααααα ααααααΎααααΈαααα»αα§ααααα Relay, Contactors, α¬ Solenoid Valves α ααΆαααΆααα·ααααα Transistor ααΈ 300V+ Spikes αααααααααΆαααααααΈαα·αααααα (When sinking/sourcing current to drive relay coils, contactors, or solenoid valves. Protects transistor outputs from 300V+ spikes that destroy output circuitry.).
- ααααααΈαααααΆ Contactor: (Contactor control circuits:) α§ααααα DC αα αααα»α Motor Starters, HVAC Contactors, ααααΏααααΆαααΈαα§ααααΆα ααααα αα ααααα ααΆααααααααααΆααΆαα½α Contactors, ααΆααααααααΆααααΆαααΎαα‘αΎαααααΉαααααΌαααΆαααΆαααΆααααΆαααααΆααα·ααααα - ααααααααααααααα’αααΈ (DC coils in motor starters, HVAC contactors, industrial machinery. When designing control panels with contactors, proper surge suppression prevents output card failuresβlearn more about) ααΆαααααΎαααΎααα·αααΆαααΆα Contactor (contactor selection and protection).
- DC Motor PWM Drives: (DC motor PWM drives:) ααααααΈ H-Bridge ααααΌα Inductive Motor Windings αα ααααααα Kilohertz α ααΈαααΌα Schottky ααααΌαααΆααααααα α·ααααααααΆαα Vf ααΆα αα·αααΆαααααααααααΏαα (H-bridge circuits switching inductive motor windings at kilohertz frequencies. Schottky diodes preferred for low Vf and fast recovery.).
- αααααααααααααα: Fuel Injector Drivers, Ignition Coil Drivers, Cooling Fan Control, Power Window Motors - ααααα»α Inductive 12V/24V ααΆαα½αα (Fuel injector drivers, ignition coil drivers, cooling fan control, power window motorsβany 12V/24V inductive load.).
- αααΌαα»α Relay Arduino/Microcontroller: (Arduino/microcontroller relay modules:) ααΆαααΆααααα»α GPIO (ααΆααααααΆααααΌαααΆαααΆαααααααααααΆαααα Β±0.5V ααΎαααΈααααΌαααααααααααααα) αα αααααΎαααα§ααααα Relay α (Protects GPIO pins (typically rated for only Β±0.5V beyond supply rails) when driving relay coils.).
- α§ααααααααααΆ HVAC: (HVAC controls:) Zone Damper Actuators, Reversing Valves, Compressor Contactors αα αααα»α Residential/Commercial Climate Control α (Zone damper actuators, reversing valves, compressor contactors in residential/commercial climate control.).
αααααΆαα guidance ααααααααΎ Coil Protection Failures, ααΌααα·αα·αααααΎα (For additional guidance on coil protection failures, review) Contactor Troubleshooting αα·α Protection Strategies (contactor troubleshooting and protection strategies).
αααααα·ααΈ Surge Arrester (Surge Arrester Applications)
ααααΆααΈαααΌααΆαααΆαααααα·ααααααααα: (System-level protection scenarios:)

- α αααααααΆααααα’αααα·αααΈαα (αααααα 1 SPD): (Main electrical service entrance (Type 1 SPD):) αααααΆααααΆαααΆαααααΌααααααΆααααΉαααΆααααααααΆαααααααααΆαα/ααααααααα αααααααααα αααα Impulse 40kA-100kA α ααΆααααααΉαααααΉαααααΌα (First line of defense against direct/nearby lightning strikes. Handles 40kA-100kA impulse currents. Understanding proper) ααΈααΆααααα‘αΎα SPD αα αααα»ααααααα’αααα·αααΈ (SPD installation locations in electrical panels) ααΆααΆααΆαααΌαααΆαααΆαααΆαααααααααααααα·αααααΆαα (ensures effective protection.).
- Distribution Panelboards αα·α Subpanels (αααααα 2 SPD): (Distribution panelboards and subpanels (Type 2 SPD):) ααΆαααΆαααΆααααααΆααααααααααααΆααααΉαααΆαααΎαα‘αΎαααααααααααααααΆααα§ααααααααααα 1 ααΌαααΉα Switching Transients αααααΆααααααΎααααα»ααααα»αα α’αα»ααααααΆα (Secondary protection against residual surges passing through Type 1 devices plus locally generated switching transients. Follow) αααααΌαααΆαααα‘αΎα SPD αα·αααΆαα’αα»αααααΆαααΌα (SPD installation requirements and code compliance) αααααΆααααΆαα’αα»αααααΆα NEC/IEC α (for NEC/IEC conformance.).
- ααααααααααΆααααααααΊααααα’αΆαα·ααα PVα Combiner Box SPDs ααΆαααΆα Inverters ααΈααΆαααΎαα‘αΎαααααααααΆαααααΈααααααα αααα»α Rooftop/Ground-Mount Installations αααααΆαααΆααααααΆαα Guidance α―ααααααΆααα αααα»αααααααΎα (Combiner box SPDs protect inverters from lightning-induced surges in exposed rooftop/ground-mount installations. Specialized guidance available in our) Solar System SPD Selection Guide (solar system SPD selection guide).
- ααααααααααααα½ααα·αα·ααααααΌαααα§ααααΆα αααα (MCCs): (Industrial motor control centers (MCCs):) ααΆαααΆα VFDs, Soft Starters αα·αα§ααααααααααΆααΈ Grid Transients αα·α Large Motor Switching α (Protects VFDs, soft starters, and control equipment from grid transients and large motor switching.).
- ααααααααααα·αααααα: (Data centers:) ααΆαααΆαααΆαα§αααααααααΆααααααααααΌαααΆα SPD Cascade αααααΆααααααααααα½α (αααααα 1 + αααααα 2 + αααααα 3) ααΆαα½αααΉαααα»α Let-Through ααΆαα (Critical equipment protection requiring coordinated SPD cascade (Type 1 + Type 2 + Type 3) with low let-through voltage.).
- α§αααααααΌαααααΆαααα: (Telecommunications equipment:) SPDs αααααΆαααΌαααααΆαααΎ GDT Low-Capacitance αα ααΎ Data Lines αααααΆααααααααααΎααααΈααΆαααΆαααΆααααααΌα αααααααααΆααααααΆα (Low-capacitance GDT-based SPDs on sensitive data lines to prevent signal distortion.).
αααααΆαα Guidance αααα’α·α SPD Specification, ααΌαααΎα (For comprehensive SPD specification guidance, see the) Ultimate SPD Buying Guide αααααΆααα’αααα ααα αΆα (ultimate SPD buying guide for distributors) αα·αααα (and understand) ααΌαααααΆαααααΉαααα§αααααααΆαααΆαααα.
ααα α»αααΌαα αα·αααΆαααααα»α
ααα α»αααΈ 1: ααΆαααααΎααααΆααααΈαααΌα Freewheeling αααααΆααααΆαααΆαααΆαααααα
ααα α»α: ααΆααααααΆααααΈαααΌα freewheeling (1N4007, ααααααααααΆαα 1A αααα, 30A surge) αα α αααα αΌαααααΆααααααΎααααΈααΆαααΆααααααΆααααΉαααΆααααααααΆααα.
α ααα»α’αααΈααΆαααΆααΆαααΆααα: α αααααααααααΆααααΆαααα 20kA-200kA ααΆαα½αααΉααααααααΆααΎαα‘αΎα <10ΞΌs. A standard diode rated for 30A (8.3ms duration) vaporizes instantly when exposed to kiloamp currents. The diode fails in short-circuit mode, creating a direct fault to ground that trips the main breaker or causes fire.
αα·ααΈααΆαααααααααΉαααααΌαα αααααααααΎ SPDs αααααΆααααααΈ UL 1449 αααααααΌαααΆαααααααααααΆααα ααααααααααΆααααΆααααα α Type 1 SPDs αα α αααα αΌαααααΆααααααααΌααααααααααΆαααααααααα 10/350ΞΌs (αααααααααΎααααααααααααΆαα) ααΆαα½αααΉαααααα·α 25kA-100kA α.
ααα α»αααΈ 2: ααΆααα»αα ααααΈαααΌα Freewheeling αα ααΎα§ααααα Relay
α ααα»αα: βRelay αααααααΎαααΆαααα’α’αααααααα 3 ααααΆαα αΎααααααααΆαααΈαααΌα freewheeling ααΌα ααααααΎααα·αααααΌαααΆαααΆαααβ
ααΆααα·ααααααΆααααααΆαα: Relay ααααΎαααΆααα αΌαααααα·ααααα PLC αααΆαααα ααα»αααΎαα‘αΎα inductive αα 300V-500V ααααα·α αααα α αααααΎαααΆαααΆαααΉααααααααααααα transistor αα·αααααααααααααΆαα±ααααΌα αα»αααΆααααΆαααΆααααααα αααααΆααααΈααααααααΌαααΆαααααα transistor αααΆααα (ααΆααΉαααΆααααα α‘αΎαααΆαααααααα βα αΆααααβ α¬ βαα·αα’αΆα ααααΌαααΆαβ) α ααΆααααα½ααααΌαα»ααα·ααααα PLC α αααΆα $200-$500 ααΌαααΉααααααααΆαααααααΆααααα αΆ αα·ααααααααΆααα αΆαααααααααα.
ααΆαααα: ααΈαααΌα 1N4007 ααΆαααααα $0.10 α αααΌαα»ααα·ααααα PLC ααΆαααααα $250 α ROI ααΆαααΆαααΆααααΆααα: 2500:1 α.
ααΆαααααΆαααααααα’αααΈααΆαααΆαααΆαααΆααααΆααααααααΆααααααΉαα§ααααα: ααααα»ααααααααααααααΆααααα αΆ contactor.
ααα α»αααΈ 3: ααΆαααααΎαααΎααααααα SPD αα»α
ααααΆααΈαααΌ AβType 3 αα α αααα αΌαααααΆαααα: ααΆαααα‘αΎα SPD α ααα»α ααααΆαααααΎααααΆαα 3kA αααααΆαααΆαααααααα αααααααααααααααααΆ βα§αααααααΆαααΆααααααΆαα½αααΉαααααΎαααΆαβ αβ
α ααα»α’αααΈααΆαααΆααΆαααΆααα: Type 3 SPDs ααααΌαααΆααα ααΆα‘αΎααααααΆααα ααααααααααΆααααααα αααααααααααΆααααΈααΆαααΆαααΆααααααααΆαααΎααΆααααααΆααααααααΆαα αααΎααα½α α αΎαα α§ααααα 3kA ααααααααΆααααΉααααααααα 40kA ααααΎαααΆααα ααΆααααα ααααααααα»ααααα ααΆααααααΆ αααΆαααααααΆαα (ααΆααΉαααΆαααα αααα»αααααααααααΈααααΈ) α αΎααα·ααααααααΆαααΆαααΆαααα.
ααααΆααΈαααΌ BβααααΆαααΆααααααααααα½α: ααΆαααα‘αΎα Type 1 αα·α Type 2 SPDs ααΆαα½αααΉααααααααααααα·ααααααααααΆαααααΆαααααΆααααΆα (α§ααΆα ααα 2 αααααααααα½αα±αα 10+ αααααααααααααΌαααΆα) α SPDs ααΆααααΈαααααΆααΆαααααΎαααΆααααα»ααααααααΆαααααΆααααααααΆαα±ααααΆαααΆαα αααααααα ααααααααα·αα’αΆα αααααααααααΆα αα·αααΆααααΆααααααα’αΆα ααΎαααΆαααα§ααααααααααααΎααααα ααααΆααα»αα.
αα·ααΈααΆαααααααααΉαααααΌαα ααααΎααΆα αα»αααααΆααααα triage matrix ααΆαααΆαααααααΆα SPD αα·αααααΎααααΉαααααΌα αααααΆαααααααΆαα’αααΈααα αααΆαααααα SPD kA. α αααααΆαααα α»αααΌαα αααα’αα»αααα ααΆαα’αα»ααααααα’αααα»ααααα»αααΆαααα‘αΎα SPD.
ααα α»αααΈ 4: ααΆααα·αα’αΎααΎααΉαααΆααααααααΈαααΆαα·αα SPD
ααΆααααααα: βααΎαααΆαααα‘αΎα SPDs ααΆαααΈ 5 ααααΆααα»α ααΌα ααααααΎαααααΌαααΆαααΆαααΆααβ
ααΆααα·αα SPDs αααααΆαααΌαααααΆαααΎ MOV ααΆαααααααΆαααααΊαααΆαα½αααΉαααααΉαααα·ααΆααααααααΈαα½ααα ααΆαααααααα MOV αααααα»αααΎαα‘αΎα ααΆαααααΆααααααΌαααΈααααΌααααααααΎαα‘αΎααα αααα»ααααααΆαα·α αααααααΈα’α»ααααΈαα αααααΆααααΈααααΉαααα·ααΆααααααααααΆαααα ααα½α 10-50 (α’αΆαααααααΎααααα·αααΆααα) ααα»αααααααα MOV ααΎαα‘αΎα α αΎααααααααΆαααααΌαααααΆαααααααααΆααΆααααααα α»αα αα ααΈαααα»α MOV αααΆαααβααΆααααααααΈααααΈ (αααααΆαα±ααααΆαααΆαααΆα αα αααα) α¬ααααααΈααΎαα αα (αα·ααααααααΆαααΆαααΆα) α.
αααααΆαααααΆαα
- ααΆαααΎαα‘αΎαααα ααααααα ααααΆα (α’αΆα ααΆααααΆαααΆαα½αααααααααα: ααααααΆ <0.5mA, degraded >5mA)
- ααΌα ααΆααααααΆαααΆα LED ααααΆααααααΌαααΈααααααααα ααΏα α¬αααα α
- ααααα»ααΆαααΆαααΆα: ααααΆαααααα, ααααΆααααΆα, ααα‘αααα’ααΌαααΆα, αααα αααα»αα’αα‘α»ααααααααα·ααααα·ααΆαααααααΆ
ααΆααα·ααΆαααααΆα: αααα½ααα·αα·ααα Type 2 SPDs ααΆαααααΆααααααΆααα αααα»αααααααααααΆαααΉααααααααΆαα αααααΆαα 2-3 ααααΆααααααα αααα»αααααααααααα αααα½α SPDs αααααΆαααΌαααααΆαααΎ MOV αααααΆααααΈααααΉαααα·ααΆααααααααα (ααΆααααααΆααααΈαααααααΆαα ααΆααα»αααααααααΈααα§αααααααααΎααααΆαααα αααααααα) α ααααααααα’αααΈ α’αΆαα»ααΆα SPD αα·αααααααΆαα αΆαα MOV ααΎααααΈαααα ααααααΆαααααααααΆααααα½αα.
αα»αααααΆαααααααΆαααΆααααααα: α ααα»α’αααΈααΆαααΆα’αααααααΌαααΆαααΆααααΈα
αααααΆαααααααΉα: ααΈαααΌα Freewheeling αα·αα§αααααα αΆααααααα·ααααααΆαααααΎααααα½αααβαα½αααΆααΆαααΆααααααΆααααΉαααΆαααααΆαααα ααααααααααααΆαααα»αααααα·ααα»αααααΆ α αΎαααααΌαααααααΎααΆαααΆαα½αααααΆαα αααα»ααααααααααααααΆααα ααΆαααΆαααααΉαααααΌαα.

αααααΆαααΆαααΆα
αααααααΆαααΈαααΌα freewheeling: ββααααααααααα’αααααΆα SPDs Type 1 αα·α Type 2 αααααΆαααααα $20,000 αααααΆαααΆααααααΆααααΉααααααΆααααα α αα αααααααα·ααααα PLC αα·αα§ααααα relay 24V αααααα»α inductive 400V ααααααΆα transistor αα·ααααα PLC α SPDs αα·αααααΎα’αααΈαααβαα½αααΆααααΌαααΆααα ααΆα‘αΎααααααΆααααΈα‘αΌααα»α α ααααααααα·ααααα‘αΆα ααααααααΈα‘αΌα’αααα αα·αααααααααΆααααα»αααΎαα‘αΎαααααα·ααααΆαααΆαα»αααα»ααααααααα ααααα: αααΌαα»α PLC $350 + 4 ααααααα αΆαα.
αααααααΆα SPDs: α§ααααα relay ααΈαα½ααααΆαααΈαααΌα freewheeling ααΆαααΆααααΆαααα’α₯αααα ααααΌααα·ααααα PLC ααΈααΆαααΆααααααααα inductive α αααααααΆααα ααααΆα 200 αααααα ααααα±ααααΆαααα 4kV αα α αααα αΌαααααΆααααααααααααααα ααΈαααΌααααααΆαααΆαααααααααααΆαα <100V, vaporize along with the power supplies, PLCs, VFDs, and control electronics connected to the unprotected panel. Cost: $50,000+ equipment replacement + weeks of downtime.
α§ααΆα αααααααΆαααΆαααΆααααααα: ααααααααα½ααα·αα·αααα§ααααΆα αααα
ααααααααα½ααα·αα·αααα§ααααΆα αααααααααααΌαααΆαααΆαααΆααααΆαααααΉαααααΌαααΆαα½αααΉαα§αααααα αΆααααααΎααααΌααα PLC αα·α HMI αα½αααΆα:
ααΆαααΆαααΆαααααα·ααααααααα (α§αααααα αΆααααα):
- Type 2 SPD (40kA, 275V) αα α§ααααααααα αΌαααααααααααααααΆααααΈαααααα ααΈαα ααΎααααΆααααΆαααΈαα½αα
- ααΆαααΆααααΈααααΉαααααΌαααΆαα½αααΉααααΆαααΈαααααααΆαααα ααΉαααααα ααΆααααααααα’ααΆα
- ααα α conductor αααααααααΆαα (#6 AWG α’αααααααΆαααααΆααααΆααααααΆααααΈ SPD)
ααΆαααΆαααΆαααααα·ααααΆαααΆαα» (ααΈαααΌα freewheeling):
- ααΈαααΌα 1N4007 ααααααΆααα§ααααα relay ααΈαα½ααααααααααααααααααα·ααααα PLC
- ααΈαααΌαααααααααααΏα (α¬ Schottky) ααααααΆααα§αααααααααα solenoid αα αααα»ααααααα·ααΈα’ααααΆααααααααα
- RC snubbers α¬ MOV suppressors αα ααΎα§ααααα contactor AC (ααΆαααααΎα ααΈαααΌα TVS αααααα·ααααααΆαααααααα·ααΈ AC)
αα·ααΈααΆαααααααΈααααααΆααααααααααααΆαααααααααΆαααααΆαααα ααααΆααααΈαα αααααΆααααααΆααααααααααΆαααΆαα’αααα·αααΈααααΌααααΌααΆα ααΌααααααΈααααΆαααααααααΆα ααΆαααΆααααΈ GFCI αα·αααΆαααΆαααΆαααα. α αααααααααα αα αααα·ααααΆααΆαααΆααααααΆααααααα: αααΆαααΆαα» MOV vs GDT vs TVS αα·ααααααΆαα α§αααααα αΆααααααααααΉαααΆααααααααααΆαα.
ααααα»αααααααααααΎαααΎααααααΆαααα·ααααα
αααΆααααΈααααααα α α·ααααα αα
ααααΎαααΎαααΈαααΌα Freewheeling αα αααα
- ααΆαααΆαααααααααΈααααα ααΈαα IGBTs α¬αα»αααΆααααααΆαα·α ααΈααΆαααΆαααααα‘αααααα·α
- ααααα»αααΊααΆα§ααααααααααΌαα, ααΌα‘αααΌα, ααα»ααααΌααα, α¬ααααααααααααFormatαα
- ααα»αααΎαα‘αΎαααααΆααααΎαα ααααΈαααααααΆαααααΌαααααααααααΈ (αααααΎαααααααα½αα―α)
- ααα»αααααα·ααααα·ααΆα <100V DC
- ααα·ααΆα’αα»ααααΆα $0.05-$2 αααα»ααα½αα ααα»α ααΆαααΆα
- αααααα·ααΈααΆαααΆαααΆααααα ααα»α ααΆαααΆα (αα½ααααα»ααα½αααααα»αα’αΆαααα»α ααα)
ααααΎαααΎαα§αααααα αΆααααααα αααα
- ααΆαααΆααααααΆααααΉαααΆαααΎαα‘αΎαααΆααααα (ααααα, ααΆαααααΌαα§αααααααααΎααααΆαα, ααΆααααααααα½αααααΆαα αΆααααααΎααααΌααα)
- ααΆαααΆααααααα’αααα·αααΈααΆααααΌα ααααααα§ααααα α¬αααααααα
- ααα»αααααα·ααααα·ααΆα >50V AC α¬ >100V DC
- ααΆαααααΎαα‘αΎαααΎαααΈ 100 joules
- ααΆαα’αα»αααααΆα UL 1449, IEC 61643, α¬ NEC Article 285 αααααΌαα±ααααΆα
- αααααα·ααΈααΆαααΆαα§ααααα 1-12 αααα»ααα½ααααααα (ααααΆαααααααααααα½α)
ααΆαααααΆαα’αααΈααα·ααα VIOX
VIOX Electric αααααααΌααααααααααΆαααΆαααΆαααΆαααΎαα‘αΎααααααααααααΆαααααααα·ααΈα§ααααΆα αααα ααΆαα·ααααααα αα·αααΆααααααΎαα‘αΎααα·αα
αααααααααα·ααα SPDα
- αααααα 1 (ααααΆαα I) SPDsα ααΆαααΆαααΆαα αααα αΌαααααΆαααα, ααα 10/350ΞΌs ααΆαααααΎααααα, ααΆαααΆαααααα 40kA-100kA, αααααααααααΆααααΆααααααΆααααΉαααααααααααααΆαα
- αααααα 2 (ααααΆαα II) SPDsα ααΆαααΆαααΆααααααα ααα αΆα, ααα 8/20ΞΌs ααΆαααααΎααααα, ααΆαααΆαααααα 5kA-40kA, DIN-rail αααΌαα»α α¬ααΆαααααααα ααΆααααααααααααααααα
- αααααα 3 (ααααΆαα III) SPDsα ααΆαααΆαααΆαα ααα»α ααααΆαααααΎααααΆαααα αα·αα§ααααααααααΆαααααααα, ααΆαααΆαααααα 3kA-10kA, ααααααααααααα’αΆα ααααΎααΆα
- αα αα αααα·ααααΆααΌαααΆαα MOV+GDTα α’αΆαα»ααΆααααααα, ααΆααααααααααααΆαααααα’, ααα»αααΆα, ααΆαααα α»αααααα·αααΆαααΎαααααααααα ααΉαααΆααα ααΆ MOV ααααα»ααααα
αα½αααα»αα αααααααα 120V-1000V AC/DC
αα·ααααΆαααααααα UL 1449 Ed.4, IEC 61643-11, αααααΆ CE, αααααααααααΆααααΆαααα‘αΎααααα’αα»αααααΆα NEC
αααααααα·αααα
- ααΌα ααΆααααααΆαααΆαααΎαααΎα (αααα = ααααα·ααααα·ααΆα, αααα α = αααα½α)
- ααΆαααααΆα ααααα ααΆαααΆααααααααααΆααααααΎαααααα·αααΎ MOV αααα ααααΆαα
- ααααΆααααααααα‘αααααα·αααΈα ααααΆααααααΆααααΆααα½ααααα αΌαααΆαα½ααααααααααααα½ααα·αα·αααα’ααΆα
- ααΆαααΆαααααα enclosure IP20-IP65 α’αΆαααααααΎαααααα·ααΈ
ααααΎααααααα ααΆααΆα‘α»αααα·ααα VIOX SPD αααααΆαααααααααα αα ααααα αα·αααΆαααααΆαα’αααΈαααααα·ααΈα αααααΆααααΆαααααΎαααααΆαααΆαααααααΆαααΆαα»αααααΆααααα ααΌααα·αα·αααααΎα αααΆααααΈααααα½ααα·αα·αααααΆαααΆααα±ααααααΎααααΆαα SPD αα·α αα·ααΈααΆααααααααααααα αααΆαααΆαααααα SPD kA.
ααΆααΉαααΆααααΆααα½ααααα½α
αααα½αα ααΎαααα»αα’αΆα ααααΎααΈαααΌα freewheeling αααα½αα±ααα§αααααα αΆααααα ααΎααααΈαααααααααΆααααΆααα?
α ααααΎαα αα·αα’αΆα αα αα½α ααα ααΈαααΌα Freewheeling ααααΌαααΆαααΆαααααααααααΆαα amps αα ααα»αααΆα (<100V) and cannot survive kiloamp lightning currents or kilovolt grid transients. A 1N4007 diode rated for 30A surge current (8.3ms duration) vaporizes instantly when exposed to a 20kA lightning impulse (<10ΞΌs rise time). Using a $0.50 diode where a $50 SPD is required results in catastrophic failure, potential fire hazard, and zero protection for downstream equipment. The 100:1 cost difference reflects entirely different protection scales and capabilities.
αααα½αα ααΎαααα»αααααΌαααΆαααΆααααΈαααΌα freewheeling αα·αα§αααααα αΆααααααα αααα»αααααααααααΆαααααααα»ααααα¬αα?
α ααααΎαα ααΆα αα αααα»ααααααα·ααΈα§ααααΆα αααα αα·αααΆαα·αααααααααααΎαααααΆααα’ααα αα½αααΆαααααΎαα»αααΆααααααααααααααααα·ααααα½ααααΈααααΆα
- ααΈαααΌα Freewheeling ααΆαααΆααααΆαααΆαα»ααΈαα½αα (αα·ααααα PLC, ααααααααΈααααα, IGBTs) ααΈααΆαααΆαααααα‘αααααα·ααααα»αααααα (αααααΎαααααααα½αα―α, <100V, amps) when switching relay coils or motor windings
- α§αααααα αΆααααααα ααΆαααΆααααααααΆααααΌαααΈααΆααααααααα½αααΆααααα (ααααα, ααΆαααααΌααααααΆα, kV, kA) α αΌαααΆααααααααα ααα αΆαααΆααα
ααΌααααΈααααΆαα½αααΉαααΆαααΆαααΆα SPD ααααα’α₯αααα αααααααΆααααΉαααΆαααΎαα‘αΎαααΆααααα ααΆααα»αα ααααΈαααΌα freewheeling αα»αα±αααα·ααααα PLC ααααα’αααααΆαααααααααα ααΉαααΆαααΎαα‘αΎα 300V+ ααΈα§ααααααααααΌααα αααα»ααα αα·α ααΌααααΈααααΆαα½αααΈαααΌααα ααΎααΆααααΆααααααΌαα ααΆααα»αα αα SPDs αα»αα±αααααααααΆααααΌαααΆαααααααααα ααΉαααΆαααΎαα‘αΎαααααααααΆαααααΈααααα αααααααααΆαααΆαααααααααααααΆααα ααααΆα αα·αααααΏαα’αα‘α·α ααααΌαα·α αααααΆα.
αααα½αα ααΎααΆαα’αααΈααΎαα‘αΎαααααα·αααΎαααα»ααα»αααΈαααΌα freewheeling αα ααΎα§ααααααααααΌαα?
α ααααΎαα αα ααααααα§ααααααααααΌααααααΌαααΆααα·αααΆααα ααααααΆαααα·αααααα½αααααααααΎα back-EMF αααααΆααααΈ V = -L(di/dt)α αααααΆααααΆααααααΌαα 24V ααααααΆαααααΆαα’αΆαααα»α αααα»α 100mH αα·αα ααααααα 480mA ααΆαααΎααα»αααΆαααααα»α 10ΞΌs αααααΎαααΆαααΎαα‘αΎα -480V α ααΆαααΎαα‘αΎααααα
- ααααααΆααα»αααΆαα semiconductor (ααααααααΈααααα, MOSFETs, IGBTs ααΎαααΈααα»αααααα, αααααΆαα±ααααΆαααΆααααΆαααααααααα)
- ααααααΆαααΆααα·ααααα PLC (ααααααααα½α $200-$500)
- αααααΆαα±ααααΆαααΆαααΆαααααα ααααΆααααααααααΆαα·α (ααΆαααΆαααααααΆααααααΏα, ααΆαααααΆααααααααΆαααααα)
- αααααΎαααΆαααααααααααα’αα‘α·α ααααΌαααΆααααα·α (EMI) αααααΆαααααααααααΈ αα·αααααΆαααααααα αααααααα
ααΈαααΌαααΆαααααα $0.10 α αΎαααΆαααΆαααΆααααΆαααααΆααα’αααααα ααααααααα½ααααααΌαα»ααα·ααααα PLC: $250+ ααΌαααΉααααααααΆαααααααΆααααα αΆ αα·ααααααααΆααα αΆαααααααααααααα αα·αααααααΎααΆααα·αα·ααα: 2500:1 α.
αααα½αα ααΎαααα»αααΉααααααααααΆααααα·αααΎα§αααααα αΆααααααααααααα»αααΆαααα α»α α αΎαααααΌαααΆααααα½α?
α ααααΎαα SPDs αααααΆαααΌαααααΆαααΎ MOV ααΆαααααααΆαααααΊαααΆααααΆααααΆαα½αααΉαααααΉαααα·ααΆαααααΎαα‘αΎαααΈαα½ααα αα·ααΈααΆααααααααα½ααα·αα·αααα
ααΌα ααΆααααΎαααΎα: SPDs αααααΆααα»αααΆαααΆαα αααΎααα½αααΆαααααΎααααααΆ LED α αααα = ααααα·ααααα·ααΆα, ααΏα = αααααααΆαααΆααααααα, αααα α = αααΆααα/αααα½αααααΆααα αα·αα·αααααΎαααααΆαααΆαααΌα ααΆαααααααΆααααααΈααΆαα.
ααΆαααααΎαααααα’αααα·αααΈα ααΆααα ααααααα ααααΆαααΆαα½αααΉαααααααααααα ααΎ conductor ααΈαααα SPD α ααααααΆα <0.5mA. Degraded: 5-20mA. Failed: >50mA α¬ααΆαα’αΆααα·ααααααΆααα.
ααΆααααα½ααα·αα·αααααΆαααΆαα ααααΎαααααΆαααααα ααααΆααα»α ααΆαααααααα α¬ααααα ααααΆααααα‘αααα’ααΌαααΆα/αα’ααΌαααΆαααα‘α»ααααααααα·ααααα·ααΆαααααααΆ (αααα αΆαααΈααΆαααΆαααΉα MOV)α ααΆαα’αΆααααααααΆαααα ααααΆαα (ααΈαα»ααα ααΆαααααα >50Β°C ααΎαααΈααΈαα»ααα ααΆαααααααα»ααα·ααααα αΆαααΈαααα αΆ)α.
ααΆααα·ααΆαααααΆα:
- ααααααααααΆαααΉααααααα αααα½ααα·αα·αααααΆαααααΆααααααΆα
- ααΆααααααΆααααααα·ααααααα αααα½ααα·αα·ααααααααΆαα 2-3 ααααΆααααα
- αααααΆααααΈααΆαα ααα»ααΆααααααα αααα½ααα·αα·αααααααΆαααααααΆααααΈααΆαααΆααααααΆααααΈααΆαααααΆααααααα α¬ααα α»αα§αααααααααΎααααΆαααααα»ααααααα 1 ααΈα‘αΌαααααα
SPDs ααααα·αααααααα½ααααα αΌαααααΆαααααααααα½ααα·αα·αααααΈα ααααΆαααααααααΌααααααΆαα ααααααααααααααααααααααΆααα ααααααααααΌαααΆαααΆααααα½α αααα’αα»ααααΆαα±ααααΆαααΆαααααΆαααΆαα»αα ααααααααααααααα’αααΈ α’αΆαα»ααΆα SPD αα·αααααααΆαααΌα αα»αααΆα.
αααα½αα ααΎααΈαααΌα Schottky α’αΆα αααα½αααΈαααΌααααΈααΈαα»ααααααααΆααααααΆαααααααα·ααΈ freewheeling ααΆααα?
α ααααΎαα ααΆα/α αΆα α αΎαααΈαααΌα Schottky ααααΌαααΆααααααα α·αααααΆααΉαααΆαααααααΆαααααααα·ααΈααΆααααΆαααααααΆαααααααααααααΎαααΆαααα’αααααΎαα
αα»ααααααααα·α
- ααΆαααααΆααα α»αααα»ααα αα»αααΆαααΆα (0.15-0.45V αααααΉα 0.7-1.5V αααααΆαααααΈααΈαα»α) ααΆαααααααααΆαααααααααΆαααΆαααα’αα‘α»αααα freewheeling
- αααααααΆααααΆαααΏαααΆααα»α (<10ns vs 50-500ns) critical for pwm frequencies>10kHz
- ααΆαααααααααΆαααΆαααααααΆαααααΌα αα αααα»αααααααΈαααααααααααα (VFDs, α§αααααααααααααααααΆαααααααααααΌα)
ααΆααα·α αΆαααΆα
- ααα»αααααααααα αααΆαααΆαααΆα (ααΆααααααΆ 40V-60V αααααΆααααΆααα Schottky αααααΉα 400V-1000V αααααΆαααααΈααΈαα»ααααααααΆα)
- α ααααααα ααααΆααααααααΆα αα ααΈαα»ααα ααΆαααΎαα‘αΎα
- ααααααΎααααααααΆα ($0.50-$2 αααααΉα $0.10-$0.50 αααααΆααααΆαααΆααααααα ααααααααΌα)
αααααΆαααααααΆαα’αααΈααΆαααααΎαααΎαα ααααΎααΈαααΌα Schottky αα αααααααααααααααααΌαααΎαααΈ 10kHz α¬αα ααααααααΆαααααΆααα α»αααα»ααα αα»ααααααΆαααααΆαααααΆαααααααααα·αααααΆαα αααααααααΆααααΆαααΆαααααα PIV ααΎαααΈααα»αααΎαα‘αΎααααααααΉααα»αα’αα·ααααΆ (ααΆαααααΆαα PIV β₯ 5Γ ααα»ααααααααααααααααΆαα Schottky)α αααααΆαααααααα·ααΈαααααααααΆα (<1kHz) with higher voltages (>48V), αααΈααΈαα»ααααααααΆα (αααααΈ 1N400x) αααααααΌααα»αααααΆαααααα-ααααΎαααΆαααΆαααααααααΎαα.
αααα½αα ααΎα’αααΈααΆααΆααα»αααααΆαααΆαα§αααααα αΆαααααααααααααΈ 1 ααααααααΈ 2 αα·αααααααααΈ 3?
α ααααΎαα α αααΆααααααΆαααααααααΈααΆααααα‘αΎα αα·ααΈααΆαααααααΆααααα αα·ααααααααΆαααΆαααΆαα
αααααα 1 (ααααΆαα I):
- ααΈααΆααα α αααα αΌαααααΆαααα αααΆαααααααα§αααααααααΎααααΆαα αα·αααΆαααααΆα αα αααααα
- αααααααααααΆααααα: 10/350ΞΌs (αααααααααΎααΆαααααΆααααααααααααααΆαα ααΆαα·ααΆααΆαααααααα)
- ααΆαααΆααααααα α αααααααα»α 25kA-100kA
- αααααααα ααααααΆαααΆαααααΌααααααΆααααΉαααααααααααααΆαα/αα ααααα ααΆαααααΌαααααΆαααααααααααα»α
- ααΆαααα‘αΎαα αααααΌαα±ααααΆα OCPD (ααΆαααΆαααΆαα ααααααΎα) αααααΆαα α»ααααααΈ ααΆααΉαααΆαααα½ααααα αΌαααααΆααΆαα½αα§αααααα αΆααααα
αααααα 2 (ααααΆαα II):
- ααΈααΆααα αααααα ααα αΆα ααααααααααααα»αααααα»α ααααααα
- αααααααααααΆααααα: 8/20ΞΌs (αααααααααααααα, ααααααΆααααΆαααααΌα)
- ααΆαααΆααααααα α αααααααα αα 5kA-40kA
- αααααααα ααΆαααΆαααΆααααααΆααααααααααααΆααααΉααααααααα αααααααααααααααΆααααααααααΈ 1 ααΌααα½αααΆααααΆαααααααΆαααααααΆααααααΎααααα»ααααα»α (ααΆαα αΆααααααΎααααΌααα ααΆαααααΌα capacitor)
- ααΆαααα‘αΎαα ααααααααΌαα αααα»α ααΆααααα DIN-rail αααΌαα»α α¬ααΆαααααααα ααΆααααααααααααααααα
αααααα 3 (ααααΆαα III):
- ααΈααΆααα α ααα»α ααααΆαααααΎααααΆαααα αα·αα§ααααααααααΆαααααααα (αα»αααααΌααα α§αααααααΆααααααα)
- αααααααααααΆααααα: ααααα½ααααα αΌαααααΆ 8/20ΞΌs (ααα»α 1.2/50ΞΌs, α αααα 8/20ΞΌs)
- ααΆαααΆααααααα α αααααααα αα 3kA-10kA
- αααααααα ααααΆααααΆαααΆαααΆαα α»αααααα ααΆαααααααααα»α let-through αα ααααα·αααΆααααα»α (<0.5kV)
- ααΆαααα‘αΎαα αααααααα α§ααααααααααΆααααα ααΆααΉαααΆαααα½ααααα αΌαααΆααααα EMI
Cascade αααααΆααααααααααα½αα ααααΏαααα·ααααΆααααααααΌαααΆαααΆαααΆααααΆαααααΉαααααΌαααααΎααααααααΆααααΈααΆαα½αααΉααααα 10+ αααααααααΆαααααΆααααΆα ααααααααΎαααααααααααΆαααΆααααααΆααααααααααα½ααααααααΆααααΆαααΈαα½ααααΆαααααααααΆαααααααα»ααααααααΆααααΆααααααΆααααααΎαααΆαα.
αααα½αα ααΎαααα»ααααααααα αααΆαααΆααααααα αααααααααΆααααΈαααΌα freewheeling αααΆαααΌα ααααα ?
α ααααΎαα α’αα»ααααααΆαααΆαααααΆααααααααα’ααααΎαααααααααααααα·ααΆααΌαααααΆααα inductors (α αααααα·αα’αΆα ααααΆααααααΌαααααΆααααΆααα)α
ααα αΆαααΈ 1βαααααα
αααα coil αααα·αααΆαα
I_steady = V_supply / R_coil
ααα αΆαααΈ 2βαααααα
ααααααααααΆααααααΌαα
αα
αααααααα»αααΆααααΎα α§ααααααααα
αΌααααααα±ααα
ααααααααα αΌααααα»αααα αααΌα
ααααΆα ααΌα
ααααα
I_peak_transient = I_steady
ααα αΆαααΈ 3βααααΎαααΎαααΈαααΌαααΆαα½αααΉαααΉααα»ααααα·ααΆαα
ααααΎαααΎαααΈαααΌααααα
αααααα
αα»αααΆαααααααααΆαα (I_F) > I_steady α.
α
αααΆαα αααααααααααα»αααΎαα‘αΎααααΆαααααΆαα α
ααααααα
α»αααΈααααααααα·αααΆαα ααΈαααΌααααααααΆαααΆαααΆαααΆααααααα
ααααααΎαα‘αΎαααααα (I_FSM) ααΌα
ααααααΆααααααααα ααααααΆαα I_F ααΆααααααΆαααααααΌαααΉααα»ααααα·ααΆααααααααααΆααα.
α§ααΆα αααα Relay 24V, ααΆααααααΉα coil 480Ξ©
- I_steady = 24V / 480Ξ© = 50mA
- I_peak_transient = 50mA (α αααααα·αααΎαα‘αΎα; ααα»αααααΎ)
- ααΆαααααΎαααΎαα 1N4007 (ααΆαααααα I_F = 1A) α αααααΆα 1A > 50mA ααΈαααΌαααααααααααΌαααΉααα»ααααα·ααΆα 20Γ α αΎαααΆααααα½ααααααααΆαααΆαααααααααΆαααΆαααα.