Introduction to Industrial Automation

Figure 3.32  The automation circuit of Figure 3.31 in order not to present the reoperation feature.

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Industrial Automation Synthesis 

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  3. The second error signal from the Buchholz device should create a breaking of the medium 

power automatic switch.

  4. The second error signal from the temperature sensor should create a breaking of the main 

low voltage switch.

  5. The horn should be able to be muted, while the fault continues to exist.

  6. A testing capability of the proper operation (without fault) of the light indications and the 

horn should be provided.

  7. When the fault is created by any kind of operation breaking, the light indications should 

exist even after the event of breaking.

The desired automation circuit is presented in Figure 3.34a. The nominal value for the operational 

voltage of the circuit is 24 V DC in order to be compatible with the voltage of a battery. To satisfy 

the seventh demand, after the event of the breaking, a proper transition in the supplying voltage 

should take place. As presented in Figure 3.34b, this is achieved by the utilization of an additional 

auxiliary relay, denoted by d

1

, which when de-energized connects the battery to the automation 

circuit.