Key Learning Points for Electrician Technician Examination: PLC Controllers, Ohm’s Law and Electrical Power, Low Voltage Components, Transformers, Diodes, etc.

Electrician Vocational Skills Level Certificate Examination Study

For the “Electrician” Level 2/Technician Learning Examination, the key learning points for PLC controllers can be focused on the following key areas:

1. 1. Basic Principles and Structure of PLC

• Working Principle: Understand the cyclic scanning working method of PLC, including input sampling, program execution, and output refresh stages, and comprehend how it achieves control over industrial equipment.
• Hardware Composition: Familiarize with the functions and roles of core components such as CPU, memory, input/output interfaces, and power supply, and understand the characteristics of different structural forms such as integrated and modular.

2. Programming Languages and Instruction Systems

• Ladder Diagram Programming: This is the most commonly used language in PLC programming, requiring proficiency in basic logic instructions (such as LD, LDI, AND, OR, etc.) and the ability to convert electrical control logic into ladder diagram programs.
• Instruction Tables and Function Block Diagrams: Understand the mnemonics and functions of instruction table languages, and master the application of function block diagrams in complex control, such as the use of PID control and motion control function blocks.

3. Control System Design and Application

• System Design Principles: Learn the design methods for PLC control systems, including hardware selection, I/O allocation, and program structure planning, to ensure system reliability, flexibility, and maintainability.
• Typical Application Cases: Through practical project cases, such as motor control, assembly line automation, and temperature control, master the application skills of PLC in different scenarios.

4. Communication and Network Technology

• Communication Protocols: Understand communication interfaces such as RS232, RS485, Ethernet, and industrial network protocols like Modbus and Profibus, and master the communication configuration methods between PLC and other devices (such as inverters, sensors, and host computers).
• Distributed Control Systems: Learn how to build distributed control systems using PLCs to achieve coordinated operation of multiple devices.

5. Fault Diagnosis and Maintenance

• Troubleshooting Methods: Master the self-diagnosis function of PLC, and learn to quickly locate and resolve common faults using tools such as indicator lights and programmers, such as input/output anomalies and program errors.
• Maintenance and Optimization: Understand the daily maintenance points of PLC systems, including hardware cleaning, software backup, and performance optimization, to ensure long-term stable operation of the system.

By systematically studying the above content, combined with practical operations and project experience, one can comprehensively enhance the application capabilities of PLC controllers to meet the work requirements at the technician level.

1. Low Voltage Electrical Appliances

1. Definition

Electrical appliances: Any components that can switch, control, protect, detect, transform, and adjust circuits.

High voltage electrical appliances: Refers to appliances with a rated voltage of 1000V and above.

Low voltage electrical appliances: Refers to appliances operating at AC voltage of 1200V, DC 1500V and below.

2. Classification

Low voltage distribution electrical appliances: Used for power supply, such as knife switches, circuit breakers, etc.;

Low voltage control electrical appliances: Used for control, such as contactors, relays, controllers, etc.;

Low voltage command electrical appliances: Used to send control commands, such as buttons, command switches, limit switches, and universal transfer switches;

Low voltage protection electrical appliances: Used for safety protection, such as fuses, thermal relays, voltage relays, current relays, etc.

Low voltage execution electrical appliances: Used for executing and driving functions in circuits, such as electromagnets, electromagnetic clutches, etc.

3. Basic Structure

1) Electromagnetic Mechanism

Composition: Consists of an attracting coil, iron core, and armature.

Armature movement modes: Direct action and snap action.

Attracting coil function: Converts electrical energy into magnetic energy, and the armature is attracted to the iron core under electromagnetic force.

Voltage coil: Connected in parallel in the circuit, with many turns and thin wire.

Current coil: Connected in series in the circuit, with few turns and thick wire.

AC coil: Short and thick, with a frame.

DC coil: Thin and long, without a frame.

2) Contact System

Contacts are used to connect and disconnect the controlled circuit.

(1) Contact forms: Point contact, line contact, and surface contact.

(2) Contact materials: Silver-plated, silver-inlaid.

(3) Arc extinction:

① Mechanical arc extinction method: Uses elastic force to quickly stretch the arc;

② Gap arc extinction method: Splits the arc and has a cooling effect. For example: longitudinal seam ceramic arc extinguishing cover;

③ Grid arc extinction method: Metal grid splits the arc;

④ Magnetic blowout arc extinction method: Under the action of electromagnetic attraction, quickly stretches the arc to extinguish DC arcs.

2. Low Voltage Distribution Electrical Appliances

Light UpLookingShare with more friends~