44. MOV for 230VAC Mains Surge Protection

Power lines carry transient voltage spikes from lightning, utility switching, and load changes on the grid. These surges can be thousands of volts and will damage or destroy electronic components. 

A Metal Oxide Varistor (MOV) is a voltage-dependent resistor. Under normal voltage, it has very high resistance and draws negligible current. When a surge exceeds its clamping voltage, its resistance drops dramatically and it absorbs the surge energy, clamping the voltage to a safe level. 

For 230VAC mains, the standard MOV rating is 275VAC maximum continuous. This provides headroom above 230V nominal (which peaks at ~325V) while still clamping effectively. Too low (250V) risks degradation from normal mains peaks; too high (300V+) means the clamp voltage is too high to protect components. 

Required: 275VAC · ≥6kA surge · ≥100J · 1-Circuit · Disc · Through Hole · Littelfuse · RoHS 

Go to DigiKey.com → Circuit Protection → Varistors, MOVs 

Apply these filters: 

• Maximum AC Volts → 275V
• Current - Surge → 6kA or higher
• Energy → 100J or higher
• Number of Circuits → 1
• Mounting Type → Through Hole
• Package / Case → Disc
• Manufacturer → Littelfuse Inc.
• Part Status → Active 

Important: MOVs degrade with each surge they absorb. After many surges, the clamping voltage drops and leakage current increases, eventually leading to thermal runaway. For critical applications, use a MOV with a thermal fuse (thermally protected MOV) or add an external fuse in series. 

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 

➡ View Matching Parts — Littelfuse, MOV, 275VAC, ≥6kA, ≥100J, Disc