A Seasonal Series on Transient Testing: Part 1

The weeks and months pass quickly this time of year.  The days are transient things, popping on the calendar and vanishing before we notice. 

This is the first of our new series with Elite's Tom Klouda and Tom Braxton. Stay tuned for more transient talk in future blogs. Read Part 2 and Part 3.

Transient events are everywhere, including the space around your product.  Can your device tolerate a voltage surge?  An electrical fast transient?  An electrostatic discharge?  A magnetic impulse?  The only way to find out is to test it, and your product will need to navigate that test.  You’ll need an experienced guide to get you there.  The International Electrotechnical Commission (IEC) provides the standards, and Elite Electronic Engineering is the guide you need to lead you through.

What are transients and where do they come from?

A transient is a short-duration pulse brought about by stored energy or a disruption in current flow.  Anyone who has experienced electrostatic discharge (ESD) when pulling off a sweater during low humidity then reached for a metal doorknob has dealt with transients.  The ESD between the metal surface and the finger is a stored-energy phenomenon. 

Voltage surges on power lines are examples of a transient brought on by current-flow disruption. When an electrical contact is interrupted by opening or closing, voltage arcs and mechanical bouncing of the contacts create random pulses.  There will be uncontrolled transients that depend on several factors: the contact type, the voltage and current levels, whether current is AC or DC, and the conductors’ geometry.  Devices in line or adjacent to the source of those transients are all vulnerable to disruption or damage.  The figure below gives a simple illustration of a switch contact being closed and the arcs that would bring about transient pulses.

Illustration showing contact closure and generation of transient pulses

These transients can cause digital logic upsets that appear as process interruptions or corrupted data.  Some transients can cause actual damage, like that shown in the picture below.  Logic upsets are more common and can range from a simple annoyance to a critical malfunction and can be minimized with error-correcting software.  Component damage is clearly a larger concern as it results in a costly repair or replacement.

Example of transient surge damage

Transients can be radiated or conducted, or sometimes both.  For example, energizing a high-current device will almost certainly generate a series of electrical fast transients (EFT) on the power circuit, which will propagate to other devices drawing energy through power cables in that building.  In addition, that event will create a momentary radiated field that can be induced into other conductors or directly into nearby devices. 

Though transients are uncontrolled when they occur, repeatable test procedures are in place that offer confidence in your product’s ability to operate normally when transients happen.

How are products tested for transient immunity?

There are different types of transients and different types of products.   The IEC standards and guidelines establish product categories and test procedures for a wide range of transient phenomena.  For example, IEC 61000-4-2 addresses ESD immunity, laying out test procedures and severity-level choices that can be chosen depending on the product type and its intended environment.  The figure below shows a typical application of the test.

esd test

Contact Discharge

Air Discharge

Level

Test Voltage (kV)

Level

Test Voltage (kV)

1

2

1

2

2

4

2

4

3

6

3

8

4

8

4

15

X*

Special

X*

Special

"X" can be any level, above, below or in between the others. The level shall be specified in the dedicated equipment specification. If higher voltages than those shown are specified, special test equipment may be needed.

 

Example of an ESD test being performed on a product and the range of voltage levels given in IEC 61000-4-2

Similarly, voltage surges are covered in IEC 61000-4-5, which spells out test procedures that are effective in predicting a product’s ability to withstand lightning surges and other sudden voltage spikes.  Voltage levels are chosen based on the product’s category and intended environment.

voltage waveform

Level

Open-circuit test voltage ±10%

KV

1

0,5

2

1,0

3

2,0

4

4,0

x

Special

NOTE: X can be any level, above, below or in between the other levels. This level can be specified in the product’s standard.


Voltage waveform applied in an IEC 61000-4-5 surge test, and the specified voltage levels

Your product will be subjected to a variety of transient events: power surges and ESD, as shown above, but also noise bursts, voltage dips, and magnetic pulses, among others, all identified in the IEC 61000-4 series of standards.

Your product’s application and intended environment will determine which tests to apply and at what levels.  The experts at Elite Electronic Engineering can explain the tests and guide you through the necessary steps toward verification. 

Be sure to follow the Elite Insider Newsletter in the coming months.  Those newsletters will review in detail the transient types, the standards that define and characterize them, and the tests that are performed to evaluate the immunity of your product. Continue with Part 2 and Part 3.

Elite Electronic Engineering draws on 65 years of experience in testing products like yours and brings its expertise and evaluation skill to answer your questions.  We’ll see the days grow shorter this season and become more transient as they go by.  Verify that your product can also see transients go by  -- Contact Elite to find out how.