2.10. Intrinsic Safety Connection

2.10. Intrinsic Safety Connection

 

The intrinsically safe pressure switch input circuits are monitored by the purge control B/D. When the robot body is pressurized, the purge control b/d activates the purge solenoid valve in the air purge unit.

Figure 2.15 Purge Control B/D

 

For intrinsically safe signals, maintain 50.0 mm distance from all other cables and connections.

 

The Maximum Input Voltage(Um) is 40Vdc for the Purge Control Board in Purge Unit. It is supplied through SMPS(SR2, SR3).

Connector CNP1 is a power supply connector for control. And connector CNP2 is a power supply connector for Relay I/O.

 

IS ground cable shall have a minimum thickness of 12 AWG (4mm2) and total 2 cables. The IS circuit of the Purge control board and intrinsic safe ground connection shall be required to connect dedicated conductor (earth bar in below figure) run to the reference ground point. The resistance of this connection must be less than 1 ohm. Earth terminals are fixed in their mountings without possibility of self-loosening and are constructed so that the conductors cannot slip out from their intended location.

And add washer between parts to prevent loosening

 

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Figure 2.16 Controller Internal Wiring

 

The pressure switches are isolated from the earth as shown in figure 2-17 below.

 

Figure2.17Pressure switches arrangement

 

Therefore, the Pressure switches and Purge control board are in compliance with IEC 60079-11 cl. 6.3.13 and IEC 60079-14 cl. 16.2.3.