Page 316 - Electromechanical Devices and Components Illustrated Sourcebook

278 Electromechanical Devices & Components Illustrated Sourcebook

Protective Boot High-Voltage Circuit

Dirt on Insulator
Reduces Stand-Off Voltage
Insulating Board

Carbon
Path
Grounded Case
Figure 16-11 Leakage Due to Carbon Paths

Figure 16-10 Leakage Due to Dirt with a glazed surface resist this type of damage, while phono-
lic and plastics are particularly susceptible.
The second process that forms carbon paths is the slow
uncontrolled arcing. The arc produces a great deal of heat and carbonizing of dirt deposits. As dirt builds on the insulator,
burns the surface of the insulator, forming carbon. If the arc small micro arcs accrue and produce localized carbon sites.
has enough energy and the insulator is sufficiently burned, a As time progresses, the carbon builds until its leak rate is
permanent short can be produced. Glass or ceramic insulators detrimental to the circuit’s continued operation.