Principle and application of common electrical components in crane

Circuit breaker, contactor, relay, thermal relay, buttons, lights, universal switch and switch is the eight most common electrical control components in the circuit. Here are some of the principles and applications of commonly used electrical components for cranes, by understanding their role in the electrical circuit to grasp the normal operation of these components.

Crane electrical components Circuit Breaker

Low voltage circuit breaker, also known as automatic air switch, can be manually switched, and can also be used to distribute electric energy, do not start asynchronous motor frequently, protect power lines, motors, etc., and automatically cut off circuits when they are seriously overloaded, short circuited or under voltage.

The character symbol of the circuit breaker is: QF

Crane electrical components Contactor

The contactor consists of electromagnetic mechanism and contact system. The most common coil voltage of contactor is AC220V, AC380V and DC220V.

The electromagnetic mechanism of contactor is composed of coil, iron core (armature) and static core. The contactor contact system is composed of the main contact and auxiliary contacts. The main contact is used to control the main circuit and the auxiliary contacts are used to control the circuit. The character symbol of the contactor is: KM

Crane electrical components Thermal Relay

Thermal relay is a relay that uses the heat effect principle produced by the current through the element to counter the time limit action.
Thermal relay character symbol: FR

Crane electrical components Intermediate Relay

The principle of an intermediate relay is a relay that turns an input signal into multiple output signals or amplifies the signal (that is, to increase the contact capacity of the relay). Its essence is a voltage relay, but it has more contacts (as many as 8 pairs), the capacity of the contact can reach 5-10A, and the action is sensitive.

When the contact numbers of other electrical appliances are not enough, the logarithm of their contacts can be extended by means of intermediate relays, and the expansion of contact capacitance can also be realized through intermediate relays.

Intermediate relay character symbol: KA

Crane electrical components Button

In practical applications, the buttons are usually selected according to the number of contacts required, the use of the occasion and the color. Commonly used LA18, LA19, LA20 and other series of buttons, suitable for AC500V, DC440V, rated current 5A, control power in the AC300W, DC70W control loop.

Button literal symbol: SB

Button color requirements:

• The "stop" button and the "hurry stop" button must be red. When the red button is pressed, the device must be stopped running or power off.
• The color of the "start" button is green.
• The buttons for "start" and "stop" alternates must be black, white or gray, and no red and green buttons should be used.
• The button of "point movement" must be black.
• "reset" (such as the reset button for protective relays) must be blue. When the reset button is stopped at the same time, it must be red.

Crane electrical components Indicator Light

The function of the indicator light:

• Indicating the running or stopping state of the equipment.
• Monitor and control the electrical power supply is normal.
• The use of red light to monitor the normal trip circuit, using green light to monitor the closing circuit is normal.

Crane electrical components Switch

The universal conversion switch is composed of an operating mechanism, a panel, a handle and a number of contacts.

The word symbol of the universal switching switch is: SA

The breaking state of the contacts when the handle is transferred to different gears is expressed in black point, with the black point of the contact closed, without a black point indicating that the contact is disconnected.