23. MOV for 3-Phase Line-to-Line Surge Protection
1. Component Purpose
A 3-phase 415VAC motor drive is subject to heavy surge transients from motor switching, VFD commutation, contactor operations, and lightning on the power distribution system.
MOVs are placed across each line-to-line pair (L1-L2, L2-L3, L3-L1) to clamp these transients. Each MOV must be rated for the full 415VAC line-to-line voltage.
The standard MOV rating for 415VAC is 460VAC maximum continuous. This provides headroom above 415V nominal (including up to +10% grid tolerance = ~457V) while still clamping effectively.
High surge current (≥10kA) and energy (≥250J) ratings are required because industrial 3-phase environments produce very high-energy transients.
Required: 460VAC · ≥10kA surge · ≥250J · 1-Circuit · Disc · Through Hole · Littelfuse · RoHS
2. How to Find It on DigiKey
Go to DigiKey.com → Circuit Protection → Varistors, MOVs
Apply these filters:
- Maximum AC Volts → 460V
- Current - Surge → 10kA or higher
- Energy → 250J or higher
- Number of Circuits → 1
- Mounting Type → Through Hole
- Package / Case → Disc
- Manufacturer → Littelfuse Inc.
- Part Status → Active
Note: You need 3 identical MOVs (one per line-to-line pair). The user selects the correct single MOV component; the BOM quantity is 3.
Tip: Larger disc sizes (14mm, 20mm) offer higher surge current and energy ratings. DigiKey shows disc size in the Package / Case field (e.g., "Disc 14mm" or "Disc 20mm"). For ≥250J, you will likely need a 20mm disc MOV.
3. Key Specifications & What They Mean
| Specification | Required | Why |
|---|---|---|
| Max AC Volts | 460V | Standard for 415VAC line-to-line. |
| Surge Current | ≥10kA | Heavy industrial 3-phase transients. |
| Energy | ≥250J | High-energy absorption for repeated surges. |
| Circuits | 1 | One MOV per line-to-line pair. |
| Package | Disc, Through Hole | Larger disc for high energy handling. |
| Manufacturer | Littelfuse | Company AVL requirement. |
| Temp Range | −40°C to +85°C | Industrial operating conditions. |
| RoHS | Yes | Compliance required. |
4. Selecting a Safe, Production-Ready Part
The filtered list will show matching parts. Before you pick one, check: Is it Active? Is stock available? Is the manufacturer reputable? Is a datasheet available?
Full checklist: How to Select a Safe, Production-Ready Component — EWskills Guide