The inverter no-load current is greater than the load current

A 75 kw micro can WIN - G9 inverter commissioning the strange phenomenon.Due to the input of the inverter is standard 50 hz sine wave,and the inverter output frequency and waveform permanent magnet motor are differs greatly with the input.Based on the principle of transformer is clip-on ammeter when measuring is dozens of times of the normal (different waveform and harmonic,frequency converter is produced by the thousand Hz level analog sine wave or square wave).If use resistor shunt type current meter measurement,error is not obvious.asynchronous motor As for runtime because of the reduced harmonic component,after feedback current waveform closer to sine wave,so the difference is small,if the series resistor shunt ammeter is basic and calculation results will be very close.(with a current transformer also can produce the same results as the clip-on sheet).Points out that caused by improper use instrument,the measuring error.Also thought that due to the problem of measuring instrument,can lead to inaccurate measurements.


Old electrician,sometimes are under the yoke of experience.But on the frequency converter operation panel display current and clip-on table by measuring current value is similar.The conventional current transformer measurement output current value is not very accurate.As noted.The output of the inverter is ten thousands of square wave voltage.After is connected to the load current is similar to sine wave.But the fundamental wave for the high frequency component.Clip-on ammeter,current transformer,will be used to conventional transformer.Due to the hysteresis effect,unresponsive to the change of high frequency current.Current transformer,the frequency converter of tailor-made,USES hall element to detect the current changes.There is plenty of strain rate.And in the subsequent circuit design has considered the characteristics of high frequency high efficiency electric motor current sampling.So only factory setting accurate,and can reflect the actual size of the current value.If not to pipe the size of the input current,the light output so much of the current,and after loading output current instead of smaller.What's your opinion? Feel free to comment.

Measurement techniques for five multimeter application skills

 Now most common triode is powder coating,how to accurately judge the triode three pin which is b,c,e? Triode b very easily measured,but how to judge which is c which is e? Here recommends three methods: the first method: for measuring triode hFE jack pointer table,first measure b pole,throw triode plug into motor vehicle spare parts the socket (b,of course,is very can plug accurate),measure hFE value,then the measuring tube upside down again,the measured values of hFE larger one,each pin insertion position is correct.The second method: to measure without hFE jack table,or is not convenient to insert the socket pipe is too big,can use this method: of NPN transistors,first measure b (the pipe is NPN and PNP b and its feet are easy to measure,isn't it?) ,put table in R x 1 k Ω gear,to connect the red pens and hypothetical e very (note that take the hand don't run into table of red pens and pen or pin),the fan motor black pens and answer the hypothetical c,at the same time hold the table with his fingers tip and the pin,will pick up the pipe,with the tip of your tongue lick a b,the header pointer should have a certain amount of deflection,if all the pens and you answer correctly,the pointer will be bigger,if wrong,the pointer will be smaller,the difference is obvious.

Which can determine pipe c and e.For PNP transistors to black pens and answer the hypothetical e very (hand don't touch the tip or pin),red pens and answer the hypothetical c,at the same time hold the table with his fingers tip and the pin,and then use the tip of the tongue lick a b,if the pens and correctly,header pointer will deflection is larger.Of course when measuring the pens and to discuss the test twice,comparative reading before final decision.This method applies to all appearance triode,convenient and practical.According to the clock deflection amplitude,but also can estimate the pipe amplification ability,of course it is by experience.The third method: first to determine the pipe after the NPN and PNP type a and b,put table at R x 10 k Ω,of NPN transistors,the black pens and connect e,red pens and pick up c extremely,the clock may have some deflection,the PNP transistors,electricalmotor1.blogspot.com black pens and c extremely,red pens and pick up e very,whose hands may have a certain amount of deflection,which in turn would have deflection.This can also determine triode c and e.But for the high pressure pipe,this method is not applicable.

Brushless synchronous generator is how to generate electricity?

Three-phase brushless synchronous generator excitation system are connected by a coaxial communication issue of ac exciter,after rotating rectifier rectifier for direct current (dc), Then sent to the generator exciting winding.Ac exciter is rotating armature type of three-phase medium frequency generator,the diesel generators prices frequency of www.dongfeng-motor.com generator frequency three times Left electricalmotor1.blogspot.com and right sides,which can improve the perkins diesel generator setexcitation response speed.Exciting winding is stationary,controlled by the automatic voltage regulator AVR excitation.Rotating rectifier Have high reliability,using the three-phase half wave bridge rectifier and three-phase full-wave bridge rectifier,firmly fixed on the rotor,with the current measurement And fault indicating device.

Family circuit design

2000 years ago,the circuit design is commonly:into the line 4-6 was,1.5 was lighting,socket was 2.5,air conditioning was 4 line.2000 years later,the circuit design is single phase ac motor commonly:into the line 6-10 was,2.5 was lighting,socket was 4,air conditioning was dedicated line 6.Air switch,also called

automatic www.facebook.com/dongfeng.motor switch,low voltage circuit breaker.Working principle is:when the current exceeds the rated current,short circuit,loss of pressure,and so on and so forth,to cut off the circuit automatically.At present,the main switch common with knife switch with porcelain insurance already was washed out () or single phase electric motor the air switch (with small leakage protection circuit breaker).Now family use DZ series air magnetic generator switch,common have the following model/specification:C16,C25,C32,C40,C60,C80,alkane,C120,such as specifications,including C said tripping current,namely the takeoff current,C32 takeoff current 32 security,for example,general installation 6500 w heater with a C32,installation of 7500 w,8500 w with C40 open water heater.

motor startup mode,auto voltage reducing total pressure direct start starting

Total pressure directly starting:At both capacity and load of power grid allows total pressure

directly under the condition of starting,can consider to use the direct starting.Advantage is that

control is convenient,simple maintenance,And more economic.Mainly used in small power motor starting from saving energy point of view,should not be greater than 11 kw motor by this method. Auto voltage reducing starting:Using the autotransformer tapped the reduced pressure,can adapt to the needs of different load starting,and can get electric vehicle motor a bigger starting torque,is a kind of is often used to starting larger capacity The decompression starting mode of the motor.Its the biggest advantage is starting torque is bigger,when the tap at 80%,starting torque can be up to 64% of direct starting.and And can be tapped to adjust starting torque.Are still widely used. Y-delta starting:For the normal operation of the stator winding for delta connection squirrel-cage asynchronous motor,if at the time of starting the stator windings into star,waiting for start to end to pick up again Into a triangle,can reduce the starting current,reduce its impact on power grid.Such starting way is called star triangle decompression starting,or simply the star delta starter (y-delta Start).Using star delta starter,starting current is only according to the delta connection directly when starting a third of the original.If direct starting at the time of starting current to 6~7 meter,ie In the star triangle is starting,the starting current is 2~2.3 times.This means using star delta starter,starting torque is reduced to the original starting directly based on the www.dongfeng-motor.com triangular connection A third.

Suitable for the occasion of no load or light load starting.And compared with any other decompression starter,its structure is the most simple,the price is the cheapest.In addition,the star

A further advantage of triangle starting way,that is,when the load is lighter,can let the motor run

in y connection.At this point,the rated torque and load can match,so Can make the motor efficiency is

improved,and thus save the electricity consumption. Soft starter:This is using the phase shift voltage regulating principle of silicon controlled to realize the regulating of the motor starting,it is mainly used for motor starting control,starting effect is good but the cost is higher.Due to the Use the thyristor,thyristor harmonic interference is larger at work,have a certain influence on power grid.Additional power fluctuations will also affect the 8500w gasoline generator thyristor conduction,special How much is in the same grid thyristor devices.So the thyristor failure rate is higher,because involving power electronic technology,thus to maintenance technicians Please also is higher. Converter:Inverter is the highest technical content of modern motor control field,most complete control function,the best control effect of motor control device,it by changing the frequency of the power grid Power saving motivation of rotational speed and torque.Because of involving power electronic technology,computer technology,so the cost is high,too high to the requirement of maintenance technicians,mainly used in accordingly Need to speed and areas of high speed control requirements.

MC Series Aluminium housing single-phase capacitor start asynchronous motors

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