Basic electrical knowledge

First, the basic knowledge of three-phase asynchronous motor
1. The motor is divided into small ( 80-315mm ), medium ( 355-630mm ) and large ( 630mm or more) according to the center height .

2 , according to the installation method is divided into: horizontal, vertical, vertical and horizontal

3. The following data is mainly marked on the nameplate of the AC asynchronous motor and its meaning is as follows:
( 1 ) Rated power ( P ): is the output power on the motor shaft. When the motor is operated under rated conditions, the mechanical power that can be output on its shaft is called the rated power. Refers to the mechanical load exceeding the rated power of the motor. At this time, the electromagnetic torque is smaller than the load torque, the slip rate is increased, and the stator current exceeds the rated value, so that the motor temperature is too high. The cause of the overload is the change of the production process conditions, the transmission belt is too tight, the center of the unit is not correct, the rotation of the shaft is not flexible, and the mechanical part is stuck. To this end, you should try to reduce the load, adjust the belt tightness, repair the mechanical equipment, and eliminate the jam.
( 2 ) Rated voltage : refers to the line voltage applied to the winding. The rated voltage is the line voltage value to be applied to the stator winding of the motor under rated operating conditions. Y series motors are rated at 380V . For motors with a power of less than 3 kW , the stator windings are all star-shaped, and more than 4 KW are triangular connections.
( 3 ) Rated current : stator winding line current. When the motor is rated for voltage and the rated power is output on its shaft, the value of the line current drawn by the stator from the power source is called the rated current.
( 4 ) Rated speed ( r/min ): Number of revolutions at rated load. The speed at which the rated operation is performed is called the rated speed.
( 5 ) Insulation class : refers to the highest temperature that the motor insulation material is tolerated . B pole 130K ( 65 °C + ambient temperature); F grade 155K ; bearing running maximum temperature 80 °C If accurate and reliable measurement, the actual temperature can be measured by infrared thermometer. Rough detection method: The operating temperature of the motor is too high, which seriously affects its service life and safe operation. If you touch the case by hand, you feel hot, but you can continue to contact for a short time, and the temperature will not rise any more, and will not overheat; if the hand is hot, it will be retracted immediately, and the small drops will drip up to make a "silk" sound, and immediately evaporate. Then the motor may be overheated.

( 6 ) Working quota : the working mode allowed by the motor. Refers to the way the motor operates. Generally divided into " continuous " (codenamed S1 ), " short-term " (codenamed S2 ), and " intermittent " (codenamed S3 )
( 7 ) Connection of the winding : Δ or Y coupling, corresponding to the rated voltage.

(8) Protection level :
Refers to the protection level that prevents the human body from contacting the rotating part of the motor, the charged body in the motor, and preventing solid foreign matter from entering the motor.
The meaning of the protective sign IP44 :
IP - characteristic letter, an abbreviation for " international protection " ;
44 - Level 4 anti-solid (to prevent more than 1mm solids from entering the motor); Level 4 waterproof (splashing water in any direction should be harmless).
(9) , LW value :
The LW value refers to the total noise level of the motor. The smaller the LW value, the lower the noise of the motor operation. The noise unit is dB .

( 10 ) Cooling channel :

When the motor is operated in a hot sun or poorly ventilated place with high temperature, it should try to improve its working environment. Such as scaffolding, clearing the dirt on the air outlet and the casing to improve the self-cooling condition of the motor.
Motors that are frequently started or reversed and run, because the intermittent time is very short, the heat generated by the large starting current cannot be dissipated, and the multiple temperature rises are superimposed, which is equivalent to several times of current and longer time overload.

4,   Model :
For example, in Y112M-4 , "Y" means Y series squirrel-cage asynchronous motor ( YR means wound-wound asynchronous motor), "112" means that the center height of the motor is 112mm , and "M" means the middle base ( L stands for long stand) , S means short machine base), "4" means 4- pole motor.
Some models on the motor base code and there are a number representing the number of cores, such as Y132S2-2 models "2" indicates that the following core length S 2 (core length 1 1).

Second, safe use of electricity

1. Safety voltage level: 6V , 12V , 24V , 36V , 42V , dual winding transformer

2 , the degree of damage to the human body: A , current intensity, current properties ( 40-60HZ ), current path, current duration

3 , leakage protector: 30Ma

Third, the loss of pressure delay protection (painting)

Class A device 1 second, Class B device 0 . 5 seconds; such as 1 ion membrane circulating alkali pump, pure water pump, light brine pump; new hydrogen chloride hydrogen pump, chlorine water circulation pump; steam alkali feed pump, etc.

 

Second, electric shock and first aid
Electric shock is the current passing through the human body, forming a closed loop with the earth or other conductors. The electric shock to the human body mainly includes electric shock and electric shock. If the human body is unable to get rid of the power immediately, it will cause difficulty in breathing, and the heart will be paralyzed and die.
The precautions to prevent electric shock are:
　　 1. Before conducting electrical work, it is necessary to verify that there is no electricity beforehand;
　　 2 , the metal casing of the electrical equipment ( such as washing machine, refrigerator, etc. ) should be well grounded;
　　 3 , insulation with electrical lines and electrical equipment must be good. The live parts of the lamp holder, socket, switch, etc. must not be exposed to prevent the human body from touching the live part;
　　 4. Do not touch or operate electrical equipment with wet hands;
　　 5 , educate children not to play with electrical equipment;
　 6. Install an electric shock protector. If someone is found to have an electric shock, try to disconnect the power supply and then give first aid. The main method of first aid for unconsciousness is to immediately perform artificial respiration and promptly ask the doctor to check it out. It is strictly forbidden to inject a strong heart.

A. Routine maintenance inspection

The main point of daily maintenance inspection of the motor is to detect the abnormal state of the equipment early and handle it in time to prevent the accident from expanding. Maintenance personnel can find abnormal phenomena according to the action and signal of the relay protection device, and can also rely on the experience of maintenance personnel to judge the accident seedlings.

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1. Appearance inspection China hot spot mold network

The first is the visual inspection. The following abnormal phenomena can be found by visual inspection: whether the external fastener of the motor is loose, whether the parts are damaged, whether the surface of the equipment is oily or corroded. Whether there are discoloration, burn marks and smoke marks at the contact points and joints of the motor, these phenomena are caused by local overheating of the motor, poor contact of the conductor or burnt of the winding. If the meter indicates that it is normal and the voltmeter is not indicating or abnormal, it indicates that the power supply voltage is unbalanced, the fuse is blown, the rotor three-phase voltage is unbalanced, single-phase operation, poor conductor contact, etc.; if the ammeter is too large, the motor is overloaded. , bearing failure, winding turn-to-turn short circuit, etc. The motor stalls, causing power failure, single-phase operation, low voltage, too small motor torque, excessive load, single-phase motor centrifugal switch failure, excessive voltage drop, bearing burnout, mechanical jam, etc. . Mold hot spot network

2 . Check with a listening stick

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By listening to the sound bar, you can hear various noises of the motor, including electromagnetic noise, ventilation noise, mechanical friction sound, bearing noise, etc., so that the cause of the motor failure can be judged. The cause of the noise is: mechanical failure: bearing failure, mechanical imbalance, loosening of the fastening screw, coupling failure of the coupling, iron core rubbing, etc.; electrical: voltage imbalance, single-phase operation, The winding has an open circuit or breakdown failure, poor starting performance, and poor acceleration performance. This article comes from China hot spot mold network

3 . Olfactory check

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The smell and smell can be found by the sense of smell. The causes of this phenomenon are: motor overheating, winding burnout, single phase operation, poor lubrication, bearing burnout, winding breakdown, etc.

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4 . Check the hot spot mold net by touch

The temperature of the motor is too high and the vibration phenomenon can be found by touching the surface of the casing by touch.
The causes of vibration are: unbalanced mechanical load, looseness of various fastening components, insufficient strength of the motor base, improper connection of coupling points, uneven air gap or mixed debris, voltage imbalance, single-phase operation, winding failure , bearing failure, etc.
The cause of the motor temperature is too high: overload, cooling air duct blockage, single-phase operation, turn-to-turn short circuit, voltage too high or too low, three-phase voltage imbalance, poor acceleration characteristics, too long start-up time, fixed rotor core Phase rubbing, poor starter connection, frequent starting and braking or reverse braking, excessive inlet air temperature, mechanical jamming, etc.
When the temperature of the motor is estimated by hand to estimate the temperature, since each person's feeling is different and subjective, it is determined by experience. Usually the relationship between human hand feeling and temperature is shown in the table.
The relationship between the surface temperature of the motor casing and the hand feeling :
Case temperature ( °C )
30 slightly colder shell is lower than body temperature, so it feels lower than body temperature
40 milder and mild
45 gentle and feel touched by hand
50 when the hand is touched by a little hot, the palm turns red
55 heat can only touch 5-6s by hand
60 very hot can only touch 3 - 4s by hand
65 very hot can only touch 2 - 3s by hand, still feel hot after leaving
70 very hot with a hand to point out the touch, can only adhere to about 3s
75 very hot with a hand to point out the touch, can only adhere to about 1--2s
80 extremely hot, thinking that the motor burned out the finger and then wanted to leave
80--90 is extremely hot, suspected that the motor burned down and felt a little hot with a little touch of the finger.

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Note: When the casing is steel, the temperature should be reduced by 5 °C .

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two. Routine maintenance check hotspot mold network forum

Routine maintenance inspections of electric motors include daily inspections, monthly or periodic inspections, and annual inspections.
In the daily inspection, the main inspection of the lubrication system, appearance, temperature, noise, vibration and abnormal phenomena, but also check the ventilation cooling system, sliding friction and the fastening of each part, carefully check the records.
During monthly or regular inspections, check whether the switch, wiring, grounding device, etc. are loose, whether there is any damaged part, if there are plans and repair measures to be proposed; check the dust accumulation, clean it in time; check the lead wire and Wiring is damaged or aging. Test the insulation resistance and record it, check the wear of the brush and the collector ring, and whether the brush is flexible in the brush holder.
In addition to the above items, the annual inspection contents should also check and replace the lubricant. If necessary, disassemble the motor for core inspection, clean or clean the grease, check the insulation resistance, dry it, and check the rust and corrosion of the parts.

This article comes from China hot spot mold network

(1) Routine maintenance of the motor

Routine maintenance is very important to reduce and avoid the failure of the motor during operation . The most important part is the patrol inspection and
Exclude any abnormal phenomenon of the root cause. Serious accident analysis after the accident, to take measures, it is reducing the number of accidents and repair
It is an indispensable technical work to improve the efficiency of motor operation when stopping the machine . The daily maintenance of the motor is very important for its normal operation , but
Motors in operation often encounter many unexpected situations , such as short circuit , overload , and equalization . In order to make the motor in these conditions
Not to be damaged , some operational protection measures must be taken
Keep the motor clean . Do not allow water , oil , dust, etc. inside the motor , and regularly remove dust inside and outside the motor .
Note that the load current should not exceed the rated value .
Pay attention to check the bearing heat , oil leakage, etc. , especially to refuel according to regulations .
The temperature rise of the motor cannot exceed the rated value .
( 2 ) Causes of asynchronous motor overload
The causes of asynchronous motor overload are roughly divided into the following cases. 1 caused by the mechanical equipment being dragged. If the water pipe of the irrigation and drainage machinery is blocked, the shaft of the machine is not the same, causing the motor load to be too large or even blocked. 2 Due to the poor working conditions of the motor itself. If the ventilation is poor, the ambient temperature is too high, the motor is partially overheated, and the motor is overheated and the insulation level is lowered. Even short circuit. 3 Due to the poor quality of the power supply network, such as the voltage is too low, the three-phase unbalance and other reasons caused by the increase in motor current.

( 3 ) Basic principles for the correct selection of electric motors
The mechanical characteristics, starting, braking, speed regulation and other control performance of the motor shall meet the requirements of mechanical characteristics and production process. The influence of the motor on the power supply quality during operation (such as voltage fluctuation, X-wave interference, etc.) shall be Within the allowable range;
According to the predetermined working system, cooling method, the motor power determined by the situation in Kiev, the temperature rise of the motor should be within a limited range;
According to the environmental conditions, operating conditions, installation methods, transmission methods, the structure, installation and protection of the motor are selected to ensure reliable operation of the motor;
Considering the cost of a single investment, the entire drive system is economical, energy efficient, reasonable, reliable and safe.
( 4 ) Basic technical requirements for electric motors
The basic technical requirements of the motor include : rated value ; working system and rating ; operating conditions ; insulation level and temperature rise ; dielectric properties ; enclosure protection level ; cooling method ; structure and installation form ; line end mark and rotation direction ; shape and installation dimensions and tolerances; limit noise and vibration; electrical performance; deadlines or reliability; apparent mass; safety performance of the motor.