Power Input Line Risks and Protection

AC power line disturbances are the cause of many

equipment failures. The damage can be as elusive as

occasional data loss or as dramatic as the destruction

of a power supply, LED Lightings, Industrial system and

consumer equipment such as ovens or refrigerators and

television sets.

Power line disturbances go by many names---transients,

surges, spikes, glitches, etc. But regardless of the

specific name, an understanding of their characteristics

and the operation of the various protection components

available is necessary to design an effective protection

circuit.

There are some popular protection components for

these power input lines. The most common over voltage

protection components are MOVs (Metal Oxide Varistor),

high power TVS (Transient Voltage Suppression) Diodes

and GDTs (Gas Discharge Tube). In this article, we are

going to discuss a new and innovative method of using

a silicon crowbar compoent known as, the SIDACtor®

Protection Thyristor component, for the main over

voltage protection solution for AC power lines.

Surge Protection

Surge protection components can be divided into two

basic types: Crowbar type devices such as GDTs and

protection thyristor type SIDACtor® components and

clamp type components such as TVS diodes, MOVs etc.

The clamp type components have faster response time

but are limited in their current handling ability because

the transient energy must be dissipated by the clamping

component. Also, the voltage drop across a clamp type

component increases as a function of the conducted

current passing through it. Thus a higher clamping

voltage threshold component will have a lower peak

current capability. (the power rating remains the same

for all components in a particular series but since power

is the product of the voltage and current, an increasing

voltage demands a decrease of current).

A crowbar type component can handle much higher

surge current because during their on-state condition,

the voltage across the component is extremely low.

These crowbarring components act as a “near short

circuit value” path shunting the transient energy away

from the protected equipment. And this, low on-state

voltage will further reduce any electrical over stress to

the protected circuit.

SIDACtor® Component in AC Power Line

Protection

Questions may arise due to the nature of the SIDACtor®

component being a crowbar protection and its

compatibility with an AC power source. This article, will

review the design parameters for selecting a SIDACtor®

component for AC power line protection. Please note

that this discussion of the SIDACtor® component use is

confined to AC power line only; it is not compatible for

high current DC supply ports. The SIDACtor® component

will reset on an AC port at the zero-crossing every half-

cycle for an AC signal. However, for high current DC

power lines, the SIDACtor® component will not reset

if the short circuit current available is higher than its

holding current parameter. Of course, if you series

SIDACtor® Component with TVS or MOV, it can be used

on DC power line too. TVS or MOV Vbr should be equal

or higher than DC max voltage

Littelfuse Pxxx0FNL and Pxxx0ME Series

SIDACtor

Component

The Littelfuse Pxxx0FNL and Pxxx0ME Series high

energy SIDACtor® component has a crowbarring

characteristic, which offers low on-state voltage

values that are much lower than the arc voltage of

the traditional GDT and it offers a much lower voltage

threshold than the clamping voltage of an MOV.

Compared to clamping silicon TVS diodes, the Pxxx0FNL

and Pxxx0ME SIDACtor® component can handle a much

higher surge current since its on-state-voltage is so low.

It also provides a much lower over-shoot characteristic

for high dv/dt or high di/dt events as compared to the

GDT, MOVs or TVS components.

The Pxxx0FNL and Pxxx0ME series have component

working voltage (V

DRM

) (also known as off-state voltage)

ranging from 58v to 450v. Referring to the I

surge

current and I

TSM

table, the Pxxx0ME provides 5000A 8/20

(peak pulse current rating) and a minimum 400A I

TSM

for 50/60Hz AC single cycle sinusoidal wave surge event

and Pxxx0FNL provides 3000A 8/20 I

and a minimum

300A I

TSM

for 50/60Hz AC single cycle sinusoidal wave

surge event.

Application Note:

High Power Semiconductor Crowbar

Protector for AC Power Line Applications

Product Series of Pxxx0ME Series in TO-218

Surge I

and I

TSM

Part Number Marking V

DRM

=5µA

@ 100V/us

min

max

P1500MEL P1500ME 140 180

P1900MEL P1900ME 155 220

P2300MEL P2300ME 180 260

P3800MEL P3800ME 350 430

P4800MEL P4800ME 450 600

TSM

50/60 Hz

8/20

1.2x50

min

5000

400

Notes:

1. Current waveform is µs

2. Voltage waveform is µs

3. P1500MEL to P2300MEL have surge rating of

5kA @ 8/20. For surge rating of P3800MEL

, it is a minimum 4kA and typical 5kA@8/20μs.

Pxxx0ME Series in TO-218

Product Series of Pxxx0FNL Series in TO-262M

Surge I

and I

TSM

Part Number Marking V

DRM

=5µA

@ 100V/us

min

max

P0640FNL P0640FN 58 77

P0720FNL P0720FN 65 88

P0900FNL P0900FN 75 98

P1100FNL P1100FN 90 130

P1300FNL P1300FN 120 160

P1500FNL P1500FN 140 180

P1900FNL P1900FN 155 220

P2300FNL P2300FN 180 260

P2600FNL P2600FN 220 300

P3100FNL P3100FN 275 350

P3500FNL P3500FN 320 400

P3800FNL P3800FN 350 430

TSM