The weak electricity system of intelligent buildings is a basic member of the intelligent group in intelligent buildings, and it is also a key component of intelligent buildings, and it is the main object of daily work of building electricians. Before the 1970s, the design of weak electricity only had telephone and radio design. By the 1980s, it added fire alarm and linkage control, shared antenna, security monitoring, and air-conditioning DDC control to its content. The design content of weak current design is expanding and expanding step by step. The technology is getting more and more new and the workload is getting bigger and bigger.
1. Why must the lighting switch be connected to the fire?
If the light switch is installed on the zero line, although the light does not turn on when the light is turned off, the phase line of the light head is still turned on, and people think that the light is off, they will erroneously think that it is in a power-off state. In fact, the ground voltage at each point on the luminaire is still a dangerous voltage of 220 volts. If people touch these actually live parts when the lamp is off, it will cause electric shock. Therefore, the switches of various lighting switches or single-phase small-capacity electrical equipment can only be secured if they are connected in series to the fire line.
2. How to install the single-phase three-hole socket correctly?
In general, single-phase electrical equipment, especially portable electrical equipment, should use three-pin plugs and matching three-hole sockets. There is a special protection zero (ground) jack on the three-hole socket. When the zero protection is used, someone often directly connects this hole in the bottom of the socket with the neutral line in the input socket. This is Extremely dangerous. Because if the zero line of the power supply is disconnected, or if the fire (phase) line and neutral line of the power supply are reversed, the metal parts such as the housing will also carry the same voltage as the power supply, which will result in electric shock.
Therefore, the dedicated ground jack should be connected to the dedicated protective grounding wire when wiring. When using zero protection, the zero line should be specifically drawn from the power supply, instead of using the zero line introduced into the nearest outlet.
3. Why are plastic insulated conductors forbidden to be directly buried in the wall?
(1) When plastic insulated wire is used for a long time, the plastic will be aged and cracked, and the insulation level will be greatly reduced. When the circuit is overloaded or short-circuited for a short time, it is easier to accelerate the insulation damage.
(2) Once the wall is damp, it will cause a large area of ​​electricity leakage, endangering personal safety.
(3) Directly buried plastic insulated wire is not conducive to line inspection and maintenance.
4. Why use a leakage protector?
Leakage protector, also known as leakage protection switch, is a new type of electrical safety device, its main purpose is:
(1) Prevent electric shock caused by leakage of electrical equipment and electrical lines.
(2) Prevent single-phase electric shock in the process of electricity use.
(3) The single-phase earth fault in the operation of electrical equipment is cut off in time to prevent electrical fire accidents caused by electrical leakage.
(4) Cut off the power supply in time to protect the equipment and personal safety, providing a reliable and effective technical means.
5. What are the main causes of electric shock?
(1) Lack of electrical safety knowledge, flying a kite near the high-voltage line, climbing high-voltage poles and gnawing the bird's nest; after the low-voltage overhead line is broken, the power line will not be turned off and used to pick up the fire line; the night-time live wiring hand touches the charged body; Plastic cover cutter.
(2) Violation of operating procedures, electrified connections or electrical equipment without taking necessary safety measures; access to damaged equipment or wires; miscarriage of live equipment; live illumination of lighting fixtures; repair of live tools with live power; electrified mobile electrical equipment; Wet hand bulbs and so on.
(3) The equipment is not qualified and the safety distance is not enough; the grounding resistance of the second-wire system is too large; the grounding wire is not qualified or the grounding wire is disconnected.
(4) The equipment is in disrepair, the wind blows off the circuit or the pole is not repaired in time; the bakelite damage of the plastic cover switch is not changed in time; the motor wire is broken and the shell is charged for a long time; the porcelain bottle is destroyed and the phase wire and pull wire are shorted. The device housing is charged.
(5) For other occasional reasons, the night-time walking touches live conductors that have fallen off the ground.
6. What rescue measures should be taken when an electric shock occurs?
In the event of an electric shock, while ensuring the safety of the ambulance itself, it is necessary to first try to get the electric shocker out of the power quickly, and immediately perform the following repair work:
(1) Untighten the tight clothing that prevents the electric shocker from breathing.
(2) Check the mouth of the person who has received the electric shock and clean up the mucus in the mouth. If there is any denture, remove it.
(3) Immediately on-site rescue, such as respiratory arrest, using mouth-to-mouth artificial resuscitation method, if the heart stops beating or irregular tremor, artificial chest compression can be rescued, and must not be interrupted for no reason.
If a second person is present in addition to the rescuer at the scene, the following work should also be carried out immediately:
(1) Provide tools and equipment for first aid.
(2) Dismiss the casual staff at the scene.
(3) Keep enough lighting on site and maintain air circulation.
(4) Report to the leader and ask the doctor to come to the rescue.
Experimental studies and statistics show that 90% of people can be saved if treatment is started from 1 minute after electrocution, and only 10% of rescue opportunities are available from 6 minutes after electrocution; 12 minutes after electrocution, The possibility of survival is minimal. Therefore, when someone is found to have an electric shock, they should fight against the seconds and use all possible methods.
7. What are the basic requirements for a leakage protector?
Technically it should meet the following requirements:
(1) The sensitivity of the electric shock protection should be correct and reasonable. The general starting current should be in the range of 15~30 mA.
(2) The operating time of the electric shock protection should not exceed 0.1 second under normal circumstances.
(3) The protector shall be equipped with necessary monitoring equipment to prevent loss of protection when the operating state changes. For a voltage type electric shock protector, a neutral grounding device shall be installed.
8. How to prevent electrical fire accidents? What should I do after a fire breaks out?
First of all, when installing electrical equipment, use qualified electrical equipment. Damaged switches, lamp caps, and damaged electrical cords must not be used. Wire connections must be securely connected and secured with insulating tape. Wiring the wiring pile heads and terminals must be tightened to prevent poor contact due to loose wiring.
Second, don't place oil, cotton, sawdust, wood, and other contaminated items near the low-voltage lines, switches, sockets, and fuses.
Before the electric fire, there is a kind of precursor. Special attention should be paid to the fact that the electric wire will scorch the insulation sheath first because of overheating, and emit a bad smell that burns rubber and burns plastic. Therefore, when you smell this odor, you should first think that it may be caused by electrical reasons. If you do not find any other reason, you should immediately switch off the power until you find out the reason and handle it properly before switching on.
In case of a fire, whether it is caused by electricity or not, first of all, we must think of ways to quickly cut off the power within the scope of the fire. Because if the fire is caused by electricity, the power supply is cut off and the fire source is cut off. If the fire is not caused by electricity, the insulation of the wire will be burned. If the power is not cut off, the burned wire will cause damage. A short circuit to the touch causes a wider range of wires to catch fire. In the event of an electrical fire, cover soil, cover sand or fire extinguishers should be used, but foam fire extinguishers must not be used because the extinguishing agent is electrically conductive.
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primarily radial and axial loads, often used in pairs, reverse installation,
inner and outer ring can be installed separately, in installation using radial
and axial clearance can be adjusted; Big cone angle mainly bear axial load
primarily of axial and radial load, is generally not used to bear alone the
pure axial load, as to the pair (end with the same relative installation) can
be used to carry pure radial load.
Tapered roller bearings are
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Range of size are below:
Single row tapered roller
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Inner diameter range: 20mm ~
1270mm.
Outer diameter range: 40mm ~
1465mm.
Width: 15mm ~ 240mm.
Double row tapered roller
bearing:
Inner diameter range: 38mm ~
1560mm.
Outer diameter range: 70mm ~
1800mm.
Width: 50mm ~ 460mm.
Four row tapered roller
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1600mm.
Diameter range: 200mm ~
2000mm.
Width: 150mm ~ 1150mm.
The precision we can produce
P0~P2.
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