Mechanical relays

Would a mechanical relay react fast enough to let each cylinder fire at the correct time ... 

Every semiconductor device has an absolute maximum voltage rating that, unlike any typical mechanical relay, cannot be exceeded even momentarily — without possibly causing its immediate destruction. So most mosfets do not allow any latitude whatsoever, in terms of their voltage ratings. 

The first computers used vacuum tubes and mechanical relays to indicate the switch positions of on... 

When using electro-mechanical relays, shelf-state, normally open contacts are used. Energizing the relay coil closes the contact, completing the circuit. De-energizing the coil returns the contact to shelf state breaking the circuit. 

Implement supplemental hardwired systems (e.g., electro-mechanical relay or trip amp) to provide an independent backup when the PE logic solver does not meet the fault tolerance requirements or probability of failure-on-demand requirements. 

In addition, there has been a steady increase of odd-shaped devices that include inductors as well as LEDs, surface-mount connectors,etc. The result has been circuit boards with a greater mix of package types and sizes. Consequently, it is considerably less expensive and time-consuming to reprogram a computer-based, machine vision system to recognize these components than it is to retool a machine based on mechanical relays, detents, and such for component placement. 

In older facihties, safety is often realized as wired logic (electro-mechanical relay) in parallel to the operational installation system completed in wired logic or on computers, depending on the age of the facility. There are typical schematics of electro-mechanical relay systems that meet the requirements for redundancy and self-test of a safety system. The stmcture is described in the context of Figure 10.1. 

Figure 10.1. Wired safely - electro-mechanical relay assembly with standardPLCf...

The interlock subsystem was designed to avoid any unsafe operations, and to promote the scram of the reactor at any time an unsafe condition is detected. It consists of "conventional" electro-mechanical relays plus 7 buttons distributed throughout the installation to promote the scram of the reactor. The signals used to scram the reactor are loss of electrical power, including individual power for any nuclear channel, neutron high flux and low period, high radiation level, loss of pneumatic system, low underpressure inside reactor room, and any open door (to access the reactor room). 

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