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8
Z-System – Zener Barriers
Product Specifications
2.1.1
Principal Assembly
Zener barriers have the following assembly.
Figure 2.3
Zener barrier function
The zener diode (ZD) limits when there is an overvoltage on the non-hazardous
area side, diverting excessive current to the ground connection. The fuse (F)
opens to prevent the transfer of unacceptably high energy into the hazardous
area. The resistor (R) limits the current in the event of a short circuit in the
hazardous area. The dedicated grounding provides the necessary low resistance
path for zener diode fault current.
ZD
Zener diode
R
Current limiting resistor
F
Fuse
Ground connection
1
Control circuit
2
Field circuit
Zone 2
Div. 2
Zone 0, 1, 2
Div. 1, 2
ZD1
R
F
ZD2 ZD3
2
1
)