13
Understanding the Engineering Challenges
A household power source can easily see surges of 600 volts. This
destroys some devices, not others. But take a 10,000-volt surge
during a lightning strike: this blows almost everything up–even
kitchen appliances. You have to watch even those devices that have
never had a problem before.
Wayne Dossey
Strategic Marketing Engineer, Bourns, Inc.
For instance, because of the magnetic field around a bolt of lightning, the lightning
does not need to strike something directly to induce voltage surges. A nearby lightning
discharge can induce a voltage surge in outside power lines coming into a building as
well as the building's metal frame. Inductive coupling inside the building can also create
voltage transients in data lines located near power lines; electrical conduits; metal building
structures; or devices that emit EMI, such as fluorescent lighting.
Power surges cause damage by creating excess heat. Although large overvoltages can
destroy practically any electronic component or device, it is the smaller, recurring surges
that cause the most frequent damage, especially for low-voltage integrated circuits (ICs)
found in control systems widely used in industrial equipment and consumer appliances.
To make these controllers more compact and efficient, engineers design them to operate
at lower voltages. Although this approach is good for product design, it also makes those
devices more susceptible to damage from power surges.
"In household
appliances, there
is no guarantee
against problems
related to overvoltage
discharges. This
constitutes damage
to the manufacturer's
image that is not easy
to assess, and in fact,
is not even normally
considered."
Ivan Fumagalli,
Project Manager,
Robertshaw
