Street Light SPD 2PIN TMOV Thermally Protected Metal Oxide Varistor 20mm 320VAC 10KA With Thermal Cutoff Built-in

Features

• Designed to facilitate compliance to UL1449 for SPD products

• High peak surge current rating up to 10kA

• Wave solderable

• Standard lead form and spacing option

• -55°C to +85°C operating temp range

• Three-lead version available for indication purposes 

Select the Right Varistors for Overvoltage Circuit Protection

Varistors, also called metal-oxide varistors (MOVs), are used to protect sensitive circuits from a variety of overvoltage conditions. Essentially, these voltage-dependent, nonlinear devices have electrical characteristics similar to back-to- back Zener diodes.

Step 1: To find the voltage rating of the MOV, allow for 20% headroom to account for voltage swell and power-supply tolerances: 24 V dc × 1.2 = 28.8 V dc. Given that no varistors have a voltage rating of exactly 28.8 V, check the datasheets for specifications for 31-V dc MOVs.

Step 2: To determine which MOV disc size to use, first identify the MOV series that minimally meet the 1000-A surge requirement. Inspecting the table above suggests a 20-mm MOV with a 31-V dc maximum continuous voltage rating (part number V20E25P) as a possible solution to meet the requirements.

Step 3: Use the pulse-rating curves (Fig. 2) in the same datasheet to determine pulse capabilities relative to the 40 pulses at the 1000-A requirement.