# S Series Standard Radial-Leaded Metal-Oxide Varistors

> Radial-leaded zinc-oxide disc varistors, 05D–20D, for board-level transient suppression; varistor voltage 18–1,100 V, max. peak current 6,500 A (8/20 µs).

- Series code: S
- Product line: [Varistors](https://www.songtian-ste.com/en/products/metal-oxide-varistors/) › Radial-leaded varistors
- Approvals: UL, CQC
- Part numbers: 1,409 · [part list (JSON)](https://www.songtian-ste.com/data/parts/s-standard.json)
- Page: https://www.songtian-ste.com/en/products/metal-oxide-varistors/s-standard/
- Chinese version: https://www.songtian-ste.com/zh/products/metal-oxide-varistors/s-standard/
- [Ask AI about this series](https://www.songtian-ste.com/en/products/metal-oxide-varistors/s-standard/?ask=Help%20me%20choose%20a%20part%20from%20the%20STE%20S%20series.)

## Key specifications

| Parameter | Value |
| --- | --- |
| Nominal varistor voltage | 18–1,100 V |
| Max. peak current (8/20 µs) | 100–6,500 A |
| Max. continuous voltage | 11–680 VAC / 14–895 VDC |
| Max. energy (10/1000 µs) | 0.4–383 J |
| Disc size | 05D–20D |
| Operating temperature | −40 °C to +105 °C |

## Engineering details

### Overview

Radial-leaded metal-oxide varistors with epoxy-coated zinc-oxide discs for board-level transient voltage suppression. Disc sizes 05D to 20D, nominal varistor voltage 18–1,100 V, max. continuous voltage 11–680 VAC / 14–895 VDC. Max. peak current 100–6,500 A (8/20 µs, one pulse), max. energy 0.4–383 J (10/1000 µs). Operating temperature −40 °C to +105 °C.

#### Series features

- Five disc sizes: 05D, 07D, 10D, 14D and 20D
- Max. continuous AC/DC voltage, varistor voltage, clamping voltage, 8/20 µs peak current and 10/1000 µs energy specified per part number
- Operating temperature −40 °C to +105 °C; 12-month storage life
- CQC and VDE certified, UL/cUL recognized to UL 1449; coverage depends on the part number

#### Typical applications

- Input overvoltage protection in appliances, controls and industrial electronics
- Transient suppression across relays, solenoids, thyristors, transistors and other semiconductor switches
- Surge suppression in telecommunications and signaling circuits
- ESD and noise-transient limiting within the pulse ratings of the part

### Specifications

|   |   |
| --- | --- |
| Function | Radial-leaded zinc-oxide varistor for transient voltage clamping; voltage-dependent shunt element with finite pulse life |
| Construction | Epoxy-coated zinc-oxide disc with radial leads |
| Reference standards | GB/T 10193 · GB/T 10194 · GB 8898-2011 · GB 4943.1-2011 · UL 1449 · IEC 61051 · IEC 60950-1:2013 |
| Disc sizes | 05D · 07D · 10D · 14D · 20D |
| Nominal varistor voltage | 18–680 V (05D) · 18–820 V (07D) · 18–1,100 V (10D, 14D, 20D) |
| Max. continuous voltage | 11–680 VAC · 14–895 VDC; per disc size and voltage code |
| Varistor voltage measured at | 0.1 mA (05D) · 1 mA (07D, 10D, 14D, 20D) |
| Varistor-voltage tolerance | K = ±10%. Some low-voltage types have asymmetric limits (see datasheet). |
| Max. clamping voltage | Specified per part number at test current IP. Compare clamping voltages only at the same current and waveform. |
| Max. peak current, 8/20 µs, one pulse | 100–6,500 A; per disc size and voltage code |
| Max. peak current, 8/20 µs, two pulses | 50–4,500 A. Not a repetitive-pulse rating. |
| Max. energy absorption, 10/1000 µs | 0.4–383 J; per part number |
| Rated power | 0.01–1.0 W, depending on disc size and voltage |
| Capacitance (typical) | 38–28,500 pF at 1 kHz |
| Waveform ratings | 8/20 µs current and 10/1000 µs energy ratings are separate tests. Do not convert either to another waveform or to repetitive duty. |
| Operating temperature | −40 °C to +105 °C |
| Storage | ≤35 °C · ≤70% RH · no corrosive gas or direct sunlight · 12 months max. |
| Dimensions, 05D | D max. 7.5 mm · T max. 3.5–5.5 mm · lead pitch F 5.0 ±0.5 mm · lead Ø d 0.5 ±0.05 mm |
| Dimensions, 07D | D max. 9.0 mm · T max. 3.5–5.5 mm · lead pitch F 5.0 ±0.5 mm · lead Ø d 0.5 ±0.05 mm |
| Dimensions, 10D | D max. 12.5 mm · T max. 4.0–7.5 mm · lead pitch F 7.5 ±0.5 mm · lead Ø d 0.7 ±0.05 mm |
| Dimensions, 14D | D max. 16.0 mm · T max. 4.0–7.5 mm · lead pitch F 7.5 ±0.5 mm · lead Ø d 0.7 ±0.05 mm |
| Dimensions, 20D | D max. 23 mm (18–68 V), 21 mm (from 82 V) · T 4.0–8.0 mm · lead pitch F 10 ±0.5 mm · lead Ø d 1.0 mm straight / 0.8 mm bent, ±0.05 mm |
| Lead forms | Long straight · single outward bend · short straight · front/rear raised |
| Lead length | Long straight ≥16 mm; short or bent 2.5–<6 mm ±0.5 mm or 6–10 mm ±1.0 mm. Coating run-down and bend height depend on the lead form. |
| Packing | Bulk or taped; taping for 5, 7.5 and 10 mm lead pitch |
| Taping | Component pitch 12.7 or 25.4 mm, depending on lead pitch · carrier width 18 mm · H0 16.5 / 17 / 19 / 20 mm |
| Hand soldering and rework | 350 °C max. · 3 s max. · solder point at least 2 mm from the coating |
| Flame class | Class C per CQC approval, for covered constructions |
| End-of-life protection | Leakage current and clamping voltage can change after surges. Coordinate upstream overcurrent protection or a thermal disconnector. |
| Further data | On request: rated-power derating versus ambient temperature · peak-current and energy derating versus pulse count, pulse width and interval · wave-soldering, preheat, cleaning and conformal-coating conditions · failure-mode data · endurance, damp-heat, thermal-cycling, vibration, lead-strength and solderability results |

### Variants

Ranges by dielectric, package and lead style within this series.

| Variant | Body dimensions | Varistor voltage / max. continuous voltage | Peak current (8/20 µs, one pulse) / energy (10/1000 µs) / rated power | Lead / land pattern | Notes |
| --- | --- | --- | --- | --- | --- |
| 05D | D max. 7.5 mm · T max. 3.5–5.5 mm | 18–680 V · 11–420 VAC · 14–560 VDC | 100–400 A · 0.4–19 J · 0.01–0.1 W | F 5.0 ±0.5 mm · d 0.5 ±0.05 mm | Smallest disc, for lower surge energy. Clamping voltage and capacitance per part number. |
| 07D | D max. 9.0 mm · T max. 3.5–5.5 mm | 18–820 V · 11–510 VAC · 14–670 VDC | 250–1,200 A · 0.9–42 J · 0.02–0.25 W | F 5.0 ±0.5 mm · d 0.5 ±0.05 mm | Compact general-purpose size. |
| 10D | D max. 12.5 mm · T max. 4.0–7.5 mm | 18–1,100 V · 11–680 VAC · 14–895 VDC | 500–2,500 A · 2.1–115 J · 0.05–0.4 W | F 7.5 ±0.5 mm · d 0.7 ±0.05 mm | Mid-size disc balancing board area, surge current and energy. |
| 14D | D max. 16.0 mm · T max. 4.0–7.5 mm | 18–1,100 V · 11–680 VAC · 14–895 VDC | 1,000–4,500 A · 4–213 J · 0.1–0.6 W | F 7.5 ±0.5 mm · d 0.7 ±0.05 mm | Higher surge current for industrial and appliance inputs. Coordinate pulse life and fail-safe protection. |
| 20D | D max. 23 mm (18–68 V), 21 mm (from 82 V) · T max. 4.0–8.0 mm | 18–1,100 V · 11–680 VAC · 14–895 VDC | 2,000–6,500 A · 11–383 J · 0.2–1.0 W | F 10 ±0.5 mm · d 1.0 mm straight / 0.8 mm bent, ±0.05 mm | Highest energy in the series. Coordinate fusing or thermal protection and the soldering process. |

### Selection guide

Select the max. continuous AC/DC voltage first. Then match varistor voltage, clamping voltage at the actual surge current, pulse shape, energy, repetition, temperature and end-of-life protection. The disc size follows from the surge stress and the required pulse life.

1. **Define continuous and temporary overvoltage**
   State nominal and max. AC/DC voltage, frequency, tolerance, grounding, harmonics, temporary-overvoltage duration and abnormal conditions. Select from the max. continuous voltage, not from the nominal varistor voltage.
2. **Define the surge waveform and surge source**
   State open-circuit voltage, short-circuit current, source impedance, current waveform (8/20 µs or other), voltage waveform (1.2/50 µs or other), polarity, repetition, interval and expected number of events.
3. **Coordinate clamping with the protected load**
   Use the clamping voltage at its stated test current and include lead and PCB inductance. Check semiconductor absolute maximum ratings, insulation, downstream capacitors and creepage at the actual surge current.
4. **Check energy, temperature and pulse life**
   An energy rating at 10/1000 µs does not define life under repetitive 8/20 µs or other pulses. Include derating versus pulse count and temperature, leakage drift and end-of-life criteria in the mission profile.
5. **Specify mechanics and fail-safe protection**
   Specify disc size, voltage code, lead form and length, packing, drawing and approval for each part number. Coordinate fusing or thermal disconnection, flame containment, spacing, soldering process and service replacement.

### Approvals & reliability

#### Approvals & qualifications

Approval coverage depends on disc size, voltage range and lead construction.

| Agency | Standard | Certificate | Scope |
| --- | --- | --- | --- |
| CQC CQC | GB/T 10193 · GB/T 10194 · GB 8898 · GB 4943.1 | 05D 19001213185 · 07D 19001213190 · 10D 19001213188 · 14D 19001213191 · 20D 19001213192 | Nominal varistor voltage 82–560 V (05D), 82–820 V (07D) and 82–1,100 V (10D, 14D, 20D), with construction-specific conditions. 10D/14D/20D certificates valid to 31 Oct 2027, subject to surveillance. |
| UL UL / cUL | UL 1449 | E330837 | Recognized component. Coverage varies by model, voltage code, lead style and coating. |
| VDE VDE | IEC 61051 · IEC 60950-1:2013 | 40023049 | Covers defined disc sizes and voltage values, not the complete series. |

Each certificate covers the types and ratings listed on it.

### Design notes

#### Select from continuous voltage, not V1mA

Nominal varistor voltage is a measurement point, not a permissible operating voltage. Include line tolerance, frequency, harmonics, grounding and temporary overvoltage when selecting the max. continuous VAC/VDC.

#### Use clamping voltage at the actual current

Residual voltage depends on surge current, dynamic resistance and interconnect inductance. Use the clamping voltage at its stated test current, then verify at the protected node on the production PCB with the actual source impedance.

#### Do not mix waveform ratings

Peak current is rated at 8/20 µs and energy at 10/1000 µs. Do not convert either to another pulse shape without a derating model from STE. Repetition and previous stress reduce capability.

#### Design for degradation and safe end of life

Leakage current and clamping voltage can change after surges. Coordinate upstream overcurrent protection or a thermal disconnector, fire containment, abnormal overvoltage and an inspection or replacement policy.

#### Coordinate the complete surge-protection stage

Define the equipment surge standard, source impedance, common and differential mode, insulation, spacing, grounding and downstream withstand. A board-level varistor alone does not establish an IEC/UL SPD class or equipment-level compliance.

#### Control lead geometry and soldering heat

Keep leads short to limit inductive overshoot without stressing the coating. Specify lead form, lead length and tape geometry with the part number. Validate wave or hand soldering, cleaning and coating. Observe the 12-month storage limit.

### Part numbering

Example ordering code. Not every combination is available.

`STE · 10 · D · 471 · K · 1 · E · N0 · F · S · B · 0 · R · 0`

| Code | Meaning |
| --- | --- |
| STE | STE prefix |
| 10 | Disc diameter: 10 = 10 mm; 05, 07, 14, 20 for the other sizes |
| D | Disc shape |
| 471 | Nominal varistor voltage: 471 = 470 V; 220 = 22 V, 112 = 1,100 V |
| K | Varistor-voltage tolerance: K = ±10% |
| 1 | Lead form: 1 = long straight; 2 = single outward bend, 3 = short straight, 8 = front/rear raised |
| E | Lead pitch: E = 7.5 mm; B = 5.0 mm, D = 10.0 mm |
| N0 | Lead length or taped height; the code depends on bulk or taped packing (code list on request) |
| F | Lead material: F = tin-plated copper-clad steel; C = copper wire |
| S | Varistor type: S = standard series |
| B | Packing: B = bulk; T = taped |
| 0 | Factory code, assigned by STE |
| R | Environmental code: R = RoHS; F = RoHS and halogen-free |
| 0 | Factory code, assigned by STE |

## Datasheets & approval documents

- [Datasheet: S series metal oxide varistors, standard type — short-form datasheet (2023-03)](https://www.songtian-ste.com/documents/source-cn/%E5%8E%8B%E6%95%8F%E7%94%B5%E9%98%BB%E5%99%A8%E7%B3%BB%E5%88%97%E4%BA%A7%E5%93%81%E8%A7%84%E6%A0%BC%E4%B9%A6/%E5%8E%8B%E6%95%8F%E7%94%B5%E9%98%BB%E5%99%A8-S%E7%B3%BB%E5%88%97%28%E6%A0%87%E5%87%86%E5%93%81%29%E7%AE%80%E7%89%88%E8%A7%84%E6%A0%BC%E4%B9%A6-202303.pdf) — PDF · Chinese · 2023-03 · 426 KB
- [Certificate: Varistor safety approval certificates (2022-11)](https://www.songtian-ste.com/documents/source-cn/%E5%AE%89%E8%A7%84%E8%AE%A4%E8%AF%81%E8%AF%81%E4%B9%A6/1-%E5%8E%8B%E6%95%8F%E7%94%B5%E9%98%BB%E5%AE%89%E8%A7%84%E8%AE%A4%E8%AF%81%E8%AF%81%E4%B9%A6%EF%BC%882022%E5%B9%B411%E6%9C%88%E7%89%88%EF%BC%89.pdf) — PDF · Chinese · 2022-11 · 4.2 MB

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