Industrial Surges
An industrial surge covers a phonemena caused by switching electrical power sources on or off.
Industrial surges are caused by:
- Starting motors or transformers
- Neon and sodium light starters
- Switching power networks
- Switch “bounce” in an inductive circuit
- Operation of fuses and circuit breakers
- Falling power lines
- Poor or intermittent contacts
These phenomena generate transients of several kV with rise times of the order of the microsecond, disturbing equipment in networks to which the source of disturbance is connected.
Electrostatic Overvoltages
Electrically, a human being has a capacitance ranging from 100 to 300 picofarads, and can pick up a charge of as much as 15kV by walking on carpet, then touch some conducting object and be discharged in a few microseconds, with a current of about ten Amperes. All integrated circuits (CMOS, etc.) are quite vulnerable to this kind of disturbance, which is generally eliminated by shielding and grounding.
Effects of Overvoltages
Overvoltages have many types of effects on electronic equipment in order of decreasing importance: Destruction
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Voltage breakdown of semiconductor junctions
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Destruction of bonding of components
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Destruction of tracks of PCBs or contacts
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Destruction of triacs/thyristors by dV/dt.
Interference with operations:
- Random operation of latches, thyristors, and triacs
- Erasure of memory
- Program errors or crashes
- Data and transmission errors
Premature ageing:
Components exposed to overvoltages have a shorter life.
Surge Protection Devices
The Surge Protection Device (SPD) is a recognized and effective solution to solve the overvoltage problem. For greatest effect, however, it must be chosen according to the risk of the application and installed in accordance with the rules of the art.
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