China
Africa
Explore chapters and articles related to this topic
Motor controllers
Published in Raymond F. Gardner, Introduction to Plant Automation and Controls, 2020
Motor controller diagrams are used to show the device wiring connections and often the control logic behind the motor operation. Electrical diagrams are either schematic diagrams or point-to-point. The relay-logic diagram, also called a ladder diagram or ladder-logic diagram, is schematic in nature and arranged in an organized, progressive manner, so that the circuit logic can be easily followed. The schematic diagram is not constrained by the physical locations of devices within the panel, and oftentimes device sub-parts are split up and located on the schematic where the logic is easy to follow. Ladder diagrams are especially conducive to both circuit design and troubleshooting. These diagrams show all wiring within the controller, plus externally connected field devices, where the field wiring is often shown connected via a terminal-board interface using dashed lines. “Ladder Diagram” (LD) is a popular PLC programming language, which is similar in philosophy to relay logic, and is discussed in Chapter 16. Figure 5.20 shows schematic-diagram electrical symbols used for the power circuit and Figure 5.21 shows electrical symbols used for control devices. Figure 5.22 shows the breakdown of a relay and contactor so its sub-parts fit logically into a ladder diagram.
Robot Controllers
Published in David D. Ardayfio, Fundamentals of Robotics, 2020
Programmable sequencers, such as printed-circuit boards, pneumatic logic modules, and pinboards, provide the capability for executing many motions in consecutive steps. Ladder or relay logic control requires a detailed description of the sequence of actions in terms of the opening and closing of relays. Programming of logic controllers involves knowing exactly how the relays must be wired together and how the logic components are to be attached to produce the required robot motion. Programmable controllers add more flexibility by permitting the control actions to be specified through a manual pendant or keyboard. Relay logic systems are inexpensive and provide enough capability for a simple, repetitive, and structured application. Pinboard-type robot control has openings arranged in rows and columns. Each row of openings represents one direction of motion for each axis, and each column represents a step in the program. In programming, a mutual setting of the pattern is effected by diode pins. The steps in the program can then be triggered by timing devices.
Research on remaining service life prediction of platform screen doors system based on genetic algorithm to optimise BP neural network
Published in Enterprise Information Systems, 2021
Xiang Ling, Suping Liu, Qin Liu, Qianzhou Wei, Yu Zhang, Zihong Shi
PSD platform unit controller is a combination of relay logic and single-chip microcomputer. As a switch device which is responsible for receiving and sending PSD action instructions, once it fails, it will directly lead to the failure of PSD. As the main part of the PSD platform unit controller, the relay is a kind of switch element with isolation function. Common parameters include: coil resistance, pull-in voltage, release voltage, contact pressure, contact resistance, rebound time, etc. Among them, the coil resistance directly determines the number of turns of the coil, while the current and turns affect the suction; the pull-in voltage refers to the minimum voltage when the relay can pull in; the release voltage refers to the maximum voltage when the release action is generated. As a key component, relay fault is the main fault of PSD platform unit controller. If the relay for opening and opening the door fails, the whole up or down sliding door cannot be opened. Similarly, if the door closing relay fails, the whole up or down sliding door cannot be closed.
Application of external flood probabilistic safety assessment methodology to Prototype Fast Breeder Reactor
Published in Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards, 2022
M. Ramakrishnan, Pramod Kumar Sharma, A. D. Roshan, A. S. Pisharady, Magesh Mari Raj, P. Chithira, A. John Arul, L. R. Bishnoi
The importance analysis of components was carried out for different flooding scenario and for each scenario dominant contributor to the CDF was identified. The Fussel–Vesely (FV) importance measure is used for identifying the dominant contributors to the CDF value for different flooding scenario. From the importance measures, it is found that, the relay logic of SGDHRS dampers is the dominant contributor to the CDF for flood levels below EL 30.0. For flood levels from EL 30.0 onwards the CDF is dominated by the human error to open SGDHRS dampers on site. This happens because the auto-opening signal for the SGDHRS dampers becomes unavailable for flood levels of EL 30.0 or above.
Safety Criteria and Dependability Management Practices: A Case Study with I&C Systems of Prototype Fast Breeder Reactor
Published in Nuclear Technology, 2018
Srikantam Sravanthi, R. Dheenadhayalan, K. Madhusoodanan, K. Devan
During normal operation, the heat generated from the core is removed with dedicated heat exchangers. After the reactor is shut down, the decay heat is removed with Operation Grade Decay Heat Removal (OGDHR) system predominantly using normal heat removal path. During the unavailability of OGDHR, the decay heat is removed with the SGDHR system. SGDHR consists of four sodium loops each with 8 MW(thermal) capacity. In each loop, the heat transfer from sodium pool to the SGDHR loop takes place through a sodium-to-sodium heat exchanger dipped into the pool. This heat will be dissipated to the atmosphere (ultimate heat sink) through sodium-to-air exchangers (AHX). To achieve very high reliability, the sodium flow in the SGDHR loop and air flow through AHX are designed to be driven by natural circulation. Both the inlet and outlet air flow paths have two sections of dampers each controlling one half of the available flow area. The damper in one section is pneumatically driven, and the damper in second section is electrically driven (motor operated). This arrangement is provided for diversity in design. Both the damper systems deploy relay logic to control opening and closing of the dampers. John Arul et al. have given design details of the system.16 The system is passive, and I&C is limited to control of dampers that restrict air flow through AHX. Apart from this, I&C is provided for monitoring sodium flow, sodium temperature, and air temperature in the loops. The important safety function of the system is to automatically “drive open” the dampers in case of reactor scram, and in case OGDHR is not operational. Salient features in SGDHR to reduce PFDAvg are: The control of dampers is segregated from monitoring function. Thus, conventional EM relay logic built with ladder diagram is used to control dampers, whereas a computer-based system is used for monitoring sodium flow, temperature, etc. This helps in simplification of safety circuit and usage of minimum number of components in the system.Electromagnetic relays are used to implement the logic rather than solid-state circuits. Relays are kept energized during normal condition and are de-energized to indicate a demand condition (since EM relays are predominantly in fail-open mode). Additionally, “Normally Open” contacts are used. Thus, dampers will open upon loss of control power supply, failures in EM relays, and cable cut.“De-energize to OPEN”–type solenoid valves are used in pneumatic dampers so that upon failure of control power supply, dampers will fully open.A counterweight is provided on pneumatically operated dampers. Pneumatic pressure is required to close the dampers. Thus, loss of pressure will lead to an opening of dampers.