50 electrical control knowledge

1． By use classification, low-voltage electrical appliances are divided into control electrical appliances, master electrical appliances, protection appliances, power distribution appliances, and executive electrical appliances.
2． According to the executive function classification, low-voltage electrical appliances is divided into contact-point electrical appliances and contactless electrical appliances.
3． According to the working principle classification, low-voltage electrical appliances is divided into electromagnetic appliances and non-power control appliances.
4． Electromagnetic mechanism by attracting coils, iron heart, iron, and other parts.
5． Electromagnetic electrical appliances are divided into DC and AC two categories, are made using the principle of the electromagnet.
6． When the knife switch is wired, the power supply inlet line should be connected to the inlet end on the side of the static socket, and the electrical equipment should be connected to the line on the side of the touch knife.
7． When using the iron shell switch, the housing should be reliably grounded to prevent electric shock accidents caused by leakage from outside
8. Contactors are mainly composed of electromagnetic systems, contact systems, and arc-killing devices.
9． DC contactors do not produce eddy current and hysteresis losses, so they do not heat up.
10． A relay is an automatic switching device that controls circuit switching based on an external input signal.
11． Relays and contractors are used to switch control and protection circuits with small currents, so the relays have no arcing device and no primary and secondary contacts.
12． Speed relays are mainly used for reverse braking control of caged asynchronous motors.
13． The proximity switch is also known as the contactless travel switch.
14． The fuse consists mainly of the melt and the melt pipe that installs the melt.
15． Circuit breakers are mainly composed of contacts, arc-out systems, and trippers.
16． Common short-circuit protection appliances are fuses and automatic air circuit breakers.
17． The commonly used overload protection appliance is a thermal relay.
18． plc’s hardware consists of a host, an I/O extension, and a variety of external devices.
19． PLC’s software system consists of system programs and user programs.
20． The process of a PLC execution program is divided into three stages: input sampling or input processing, program execution, and output refresh or output processing.
21． Usually a PLC instruction consists of a step number, a mnemonic, and a component number.
22． Relays in PLC equivalent circuits are not actual relays and are often referred to as “soft relays” to distinguish them from actual relays.
23． In the state transfer diagram, each state provides three functions: drive load, specify transition conditions, position new state.
24, low-voltage electrical appliances refer to the operating voltage in the DC 1500V or AC 1200V or below a variety of electrical appliances.
25, the contact according to its main contact through the type of current, can be divided into DC contactor and AC contactor.
26, relay contactor control circuit is composed of a variety of buttons, travel switches, relays, contactors, fuses, and other components, to achieve the power drag system start, speed, braking, reverse control, and protection, to meet the production process for power drag control requirements.
27, the thermal relay is the use of the thermal effect principle of the current to work the protection of electrical appliances, it is mainly used in the circuit as a three-phase asynchronous motor of the overload protection.
28, speed relay is mainly used as reverse brake control.
29. Time relay refers to the electrical appliance used to achieve contact delay on or delay disconnect control.
30, the machine electrical control system is made up of many electrical components following certain requirements, to achieve automatic electrical control of the machine. To facilitate the design, analysis, and research of the control system, installation and commissioning, use, and maintenance, it is necessary to connect the electrical components and their interconnection, with the state-mandated text, symbols, and graphics. This diagram is an electrical control system diagram. The electrical control system diagram includes an electrical schematic, an electrical component wiring diagram, an electrical component layout diagram three kinds of diagrams.
31, in the machine electronic control, short-circuit protection with the fuse, overload protection with thermal relay, overcurrent protection with the Overcurrent relay . ..
32, PLC each scanning process is divided into three stages, namely: input sampling phase, program execution stage, and output refresh three stages.
33, the electrical control chart is generally divided into the main circuit and control circuit two parts.
34, the structure of the contact form has bridge contact, finger contact.
35, contactors are used to switch on or off the MAIN and high-capacity control circuits frequently over long distances.
36. The rated on-off capability of the contactor refers to the current value of its main contact that is reliably switched on and off under the prescribed conditions.
37. Relay is a control element that utilizes various physical changes to convert changes in power or non-electricity into electromagnetic forces or to make step changes in the output state, thereby causing the movement of other devices or devices in the same circuit or another circuit using its contacts or mutations.
38, relay adjustment device to change the relay’s action parameters.
39, low-voltage electrical appliances by use: low-voltage distribution appliances, low-voltage control appliances.
40, electromagnetic relay reflects the electrical signal, when the coil reflects the voltage signal, for the voltage relay, when the coil reflects the current signal, for the current relay.
41, electromagnetic voltage relay coil and connected to the circuit voltage, used to reflect the size of the circuit voltage.
42, electromagnetic current relay coils are connected in the circuit, used to reflect the size of the circuit current.
43,three-phase rat cage-type asynchronous motor Y-Y-zi buck start-up current is 1/3 times the direct start-up current, this method can only be used for stator windings using the method of the motor.
44, CMC-MX soft starter starting mode: current limit start, voltage ramp starting;
45, Xichi one body high-voltage solid-state soft starter is the switch cabinet and starting cabinet into one.
46, when selecting the contactor should start from its working conditions, control the AC load should choose the AC contactor, control the DC load should choose the DC contactor.
47. When the contactor is selected, the rated operating voltage of its main contact should be greater than or equal to the voltage of the load circuit, the rated operating current of the main contact should be greater than or equal to the current of the load circuit, and the rated voltage of the attracting coil should match the voltage of the control circuit.
48. The role of intermediate relays is to turn an input signal into multiple output signals or to amplify the signal.
49,cage-type asynchronous motor commonly used braking methods are electrical braking and mechanical braking.
50, according to the national standard, the “stop” button must be red, “start” button must be green.