1. Low-voltage electrical classification
Definition: The electrical components that control the regulation and protection in the power lines of 1200V or DC 1500V are called low-voltage electrical appliances.
Low-voltage electrical appliances can be divided into low-voltage distribution electrical appliances and low-voltage controllers:
Low-voltage power distribution equipment: This type of electrical equipment includes knife switches, transfer switches, fuses, automatic switches and protective relays. It is mainly used in low-voltage power distribution systems. It requires accurate operation, reliable operation and sufficient in the event of system failure. Thermal stability and dynamic stability.
Low-voltage control appliances include control relays, contactors, starters, controllers, voltage regulators, main electrical appliances, varistors and electromagnets. They are mainly used for power transmission, requiring long life, small size, light weight and reliable operation.
The correct choice of low-voltage electrical appliances:
Safety principle: Safe and reliable use is the basic requirement for any switchgear; ensuring the reliable operation of the circuit and the electrical equipment is an important guarantee for the normal operation of production and life.
Economic principles: Economic considerations can be divided into the economic value of the switchgear itself and the value generated by the use of switching appliances. The former requires reasonable choice and application; the latter considers that it must be reliable in operation, not to cause production failure or damage to equipment, endangering personal safety and other economic losses.
Classification of general types of low-voltage electrical appliances:
Knife switch
Function: It is used for isolated power supply in equipment power distribution, and can also be used for infrequently switching on and off the rated current below the load.
Features: The fault current cannot be cut off and can only withstand the electric power caused by the fault current.
Transfer switch
Function: It is an electrical appliance for two or more power sources or load conversion.
Features: Simplify the control loop or measurement circuit and avoid operational errors.
Fuse
Definition and function: An appliance for breaking or short-circuit protection by means of a melt that melts when the current exceeds a limit value.
Characteristics: The fuse's fusing time is related to the magnitude of the fusing current, and its law is inversely proportional to the square of the current.
Master device
Definition and function: It is used to switch control circuits, through which commands or signals are sent to control the start, run, stop or state change of the electric drive system and other control objects. It is an electric appliance that specifically sends action commands.
Features: Mainly used to control the electromagnetic coil (relay, contactor, etc.) electromagnetic coil and power supply connection and disconnection.
Type: According to its function, it can be divided into control button (button switch), universal transfer switch, travel switch, master controller, other main controller (such as foot switch, reverse switch, etc.).
Contactor
The definition of the contactor: an electric appliance that can automatically control the starting, running and stopping of the motor from a long distance.
Classification: The contactor is divided into two types: AC contactor and DC contactor according to the type of current it controls.
Structural composition: contact system, arc extinguishing system, magnetic system, housing, auxiliary contacts (usually two or more pairs, normally open and normally closed)
Working principle: The coil on the iron core generates a magnetic force by a current to attract the movable armature, and the moving contact contacts the static angle head through the lever to open the circuit.
thermal relay
Function: to protect the overload of the motor and control the heating state of other electrical equipment.
Category: Bimetal and thermistor
Structural composition: bimetal, heating element, guide, normally open or normally closed static contact, reset adjustment screw, adjustment knob, compression spring, push rod, etc.
Working principle: The current is heated to make the contacts act.
Automatic switch (air circuit breaker)
Function: When the circuit is abnormal, such as overload, short circuit and under voltage, it can automatically break the electrical equipment of the circuit.
Structural composition: sensory component, transmission component, actuator
Working principle: When the circuit is short-circuited, overloaded or under-voltage, the magnetic coil generates suction after the specified value range is exceeded, so that the armature acts, and the lock buckle is tripped, thereby breaking the main circuit.
Leakage protector (electromagnetic leakage switch)
Function: It is used to protect personal electric shock and to prevent fire accidents caused by electrical equipment or wiring.
Structural composition: zero sequence current transformer, leakage release, main switch, insulated housing
Working principle: detecting components. The detected leakage or leakage current is converted into a voltage or current of the secondary circuit, causing the drive release to operate, and an electric shock or leakage signal is generated, so that the power is cut off.Wire harnesses are commonly used in the electronics industry, the automotive industry, in the manufacture of construction machinery and industrial equipment, as well as in the manufacture of white goods such as washing machines and dryers, refrigerators, and other household appliances.A industrial wire harness is typically designed to simplify the manufacture of a larger component, and is designed based on the geometric and electrical requirements of the equipment it is to be installed in.
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