The classification of electrical fault

According to the composition characteristics of electrical devices,from looking for electrical fault,from the viewpoint of the common electrical fault can be divided into three categories: 1.The power failure: lack of power,voltage,frequency deviation,the polarity of by phase line and neutral line and reverse,the lack of a power supply,phase sequence change,ac/dc mixed.2.The circuit fault: break,electric vehicle motor short circuit,short,grounding,connection error.3.The equipment and component failure: overheating burned,can not run,electrical breakdown,performance becomes worse.According to the fault phenomena analysis the cause of the problem,the key is to find electrical fault.Is based on the analysis of the basic theory of electrician,is for the electrical device structure,principle,performance,fully understand,ac electric motor is with the combination of the actual fault.


The causes of an electrical fault may be a lot of,it is important to find out the main reason in many reasons,and use approach to troubleshooting.For example,a three- phase cage asynchronous motor fault functioning,whatever the case,is the most concentrated performance motor does not work,but is not necessarily in the motor fault,and may be a power failure,may also be the failure of circuit or equipment and components.That is to say,the same failure form,failure of a variety of reasons.In these reasons,which is what reasons make the motor can't work,even after a deeper and more detailed analysis.For example: if the motor is used for acmotortrading.blogspot.com the first time,it should check power supply,circuit,the motor and load analysis; If the motor is used for the first time after repair,it should start from the motor itself check analysis; If the motor is running for a period of time suddenly can't run,it should check points off power supply and control components.Through the above process,then determine the specific cause of motor fault.

Repair and matters needing attention

After find out the fault point electrical equipment,will start to repair,commissioning,records,etc.,and then consign is used,but must pay attention to the following: (1) find out the fault point and permanent magnet generatorrepair failure,can't find the fault points should be paid attention to as a search for the end of electrical motor the fault must be further find out the root cause of the failure analysis.(2) find out the fault point,must according to different fault condition and the location corresponding to the correct

repair method.(3) in the motor run capacitor repair work of fault point,under normal circumstances should try to be recovered.(4) electrical fault repair finished,need electricity commissioning,cooperate with the operator,to avoid new failures.(5) after each troubleshooting,electricalmotor1.blogspot.com should be

timely sum up experience,and make the maintenance records.Records include: industrial machinery

model,name,number,the date of the failure,failure phenomena,parts,damage of electric appliance,the

cause of the problem,after the repair measures and repair operation,etc.Record purpose: as a file as

a reference for future maintenance,and through the analysis of all previous failures,take the

corresponding effective measures to prevent similar accidents from happening again or improvements

for the design of the electric equipment itself,etc.

Ac motor

To realize the mechanical energy and electrical energy transformation of mini electric motor mechanical communication. Ac motor is the most commonly used motor. Due to the status of the motor can pass, the same motor as a generator and motor. Ac motor according to the varieties could be divided into two types: synchronous motor and induction motor. Synchronous motor rotor rotational speed n s the same as the rotating magnetic field rotation speed, is called the synchronous speed. N s and pick up the frequency of the alternating current polarity logarithmic relationship between p and f motor for n s = f/p. In China, the power frequency 50 hz, so two pole motor synchronous speed is 3000 RPM, quadrupole motor synchronous speed is 1500 RPM, and so on. The speed of the rotor asynchronous motor is wholesalemotor.blogspot.com always less than or more than the speed of the rotating magnetic field, the difference between the two (called slip) usually within 10%. 

The speed of the ac motor (either synchronous or asynchronous) the restriction of the power frequency, and speed control is difficult. Ac motor generally adopts three-phase system, because of the three-phase ac motor compared with the single phase motor, no matter in such aspects as performance index, raw material use and price has obvious advantages. Large capacity synchronous motor are turning pole type, namely the rotor magnetic pole, is produced by passing a dc excitation winding, and synchronous machine very logarithm is the logarithmic rotor magnetic pole. Eight pole motor rotor is eight pole, 2 p = 8, namely the motor with 4 poles. Steam turbine generator is non-salient pole Dongfeng Electric type motor, more commonly a logarithmic rarely, generally for 1, 2, and n = 60 f/p, so his speed is high, up to 3000 RPM (frequency), and the number of considerable ac electric motor hydro-generator, for salient pole rotor structure, the process is more complex, because the number of his lot, so he has a very low speed, maybe only a few turns per second.

How to change the direction of rotation of three-phase motor

Direction of the rotation of the rotor of the motor is determined by the direction of rotation of the

asynchronous motor stator rotating magnetic field established,and the direction of

the rotating electricalmotor1.blogspot.com magnetic field with the three phase

current phase sequence.This www.facebook.com/guohong.trading changed the current

phase sequence that change the direction of the rotating magnetic field,synchronous

motorwhich changed the direction of rotation of the motor.

The estimation of three-phase ac asynchronous motor rated current

Whether need to reverse braking mode;6.Use environment and conditions,in indoor or

outdoor,temperature,humidity,size,how much dirt or dust,corrosive gas,explosive gas or liquid such as fever or smoke.Possible reasons: the power supply voltage is too low,three-phase ac asynchronous motor rated current estimates under the rated load caused by temperature rise is too high;Poor ventilation Or the environment humidity is too high;Motor overload or single phase operation;Number of frequent motor starting or positive &negative too much;Stator and rotor phase.2.4 low insulation resistance.Possible reasons: winding be affected with wholesalemotor.blogspot.com damp be affected with damp or pour water into the motor internal;There is dust on winding,oil engine-grease;The stator winding insulation aging.Often encountered in the practical work of agricultural machinery with dynamic problems,that is The choice of three phase asynchronous motor.On the premise of meet the requirements of production machinery,the basic principle of choosing motor is practical,economic and security,there are four factors to consider: type,rated power,rated voltage,rated speed.A,familiar with the requirement to the power of agricultural machinery to understand: (1) driving load the required power;(2) the type of work load,the load Is a continuous work,a short work,work load change or intermittent,etc.;(3) whether you need load demand work speed and speed regulation,there is a

speed adjustment and stepless speed regulation,etc.(4) starting way,frequency;(5).Second,according to

the requirement of the load motor asynchronous motor with squirrel cage and winding type two

kinds,selection method is as follows: 1) priority choose low price, Simple structure,convenient

maintenance of Y series three-phase ac squirrel-cage rotor asynchronous motor,but the downside is

speed control difficulty,low power factor,the starting performance is poorer.As a result,the

three phase generator mechanical properties is hard and no special requirements of the general production machinery and drag,such as agricultural and sideline products processing,ventilator,conveyor,conveyor belt,water pump is widely used in production machinery Pan.

The basic structure of three phase asynchronous motor three-phase asynchronous motor is made up of stationary stator and pivoting of rotor in two parts.A.the stator's structure: the three-phase asynchronous motor stator consists of frame,the stator core and stator

winding.B.rotor structure: the three-phase asynchronous motor rotor by the rotor iron core and rotor

winding and the rotor shaft parts.C.three-phase asynchronous motor by the bearing cover,junction

box,end cover,the stator core,stator winding,shaft,bearings,rotor,fan and casing.Common fault analysis 2.1 2 motor starting difficulty,rotational speed is low.Possible reasons: low power supply voltage;Originally the Angle of by misconnection into a star;The squirrel-cage rotor cage bar end sealing off,loose or break.2.2 after connect electric Machine can't start,have a hum.Possible reasons: not all plug in into single-phase starting;Motor overload;Being dragged mechanical stuck;Wound rotor motor rotor circuit broken into bolt;Inside the stator head end location wrong,or have a break,short circuit.Rated current of the motor.The motor rated current (A) is A "double motor power",namely "A kw two amps.tong Often refers to the commonly used 380 at about 0.8 v,the power factor of three-phase asynchronous motor ",the number will kw and double "is the rated current of the motor.For example: a model for Y112M - 4 three-phase motor fan asynchronous motor,the power rating of 4 kw,rated voltage of 380 v,so its rated current is about 8 a left and right sides.2.The experience formula of the motor rated current (A) = motor capacity X 2 (kW).The simplified formula and empirical formula is the use of the result is consistent,calculate the rated current and motor nameplate was very close to the actual current values,conform to the practical requirements.For example: "a Y132S1 -2 kW motor,using the simplified formula or empirical formula is the rated current of 5.5 x 2 = 11 a.Rated (three-phase ac asynchronous motor Current estimates and experience formula @ Li Enhua is < > in actual work,usually because of the damage and loss of the three-phase asynchronous motor nameplate,or the lack of practical maintenance electrician manuals and other data,can't know for sure the rated current of the motor.

2.2 kw YC/YC2 capacitors series single phase ac electric motors

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