Inverter www.simo.org.cn<br>

AC asynchronous motor frequency conversion principle:

Inverter is the use of power semiconductor devices on-off function voltage and frequency of continuous AC voltage, frequency adjustable AC power supply.

The inverters currently used mainly use the cross-direct payment method (VVVF inverter or vector control inverter), and the industrial frequency AC power is first converted by the rectified DC power, and then the DC power supply frequency, voltage control AC power of the electric motor.



The inverter is mainly composed of rectifying DC (ac), filtering, rectifier (dcac), braking unit, driving unit, and detection unit micro-processing unit.







- direct payment

Rectifier circuit: A full-wave rectifier bridge that cannot be controlled by vd1-vd66 rectifier diodes. Rated 380V power supply, the diode reverse value should generally be reduced by 1200V voltage, the forward current of the diode is 1.414-2 times the rated current of the motor.



(2) Inverter components

Capacitor c1:

Absorption capacity, rectifier circuit output pulsating DC voltage, must be filtered,

A transformer is a common electrical device that can use some number of alternating voltages to convert the frequency of another numeric alternating voltage, and can also change the value of alternating current and impedance or the phase of change.

Varistor:

There are three roles, one voltage protection, two lightning resistance requirements, and three security testing needs.

Thermistor: Overheat protection

hall:

Installed in the sale includes two stages for detecting the value of the output current. Select about 2 times the rated current rating of the motor.

Charging resistance:

The function is to prevent the short-circuiting of the instant-on capacitor to ground, and the second end of the storage capacitor voltage 0v before the start of the capacitor is burned out; therefore, the current (initiation) is short-circuited to the ground capacitor. Without a rectifier bridge and an electrolytic capacitor between the charging resistors, the 380V power supply is directly shorted to ground. Infinitely a rectifier bridge now causes the rectifier bridge to blow up. The larger the power of the general inverter, the smaller the charging resistance. The general charging resistance range is: 10-300ω.

Storage capacitor:

Also known as the electrolytic capacitor, the main function and filtering of the energy storage charging circuit. The Pn voltage operating voltage range is 430VDC-700VDC, while the high voltage capacitor is about 400VDC, in order to meet the demand pressure must be two 400VDC capacitor series 800VDC. Ability to choose University of Florida at age 60 or more /

Balanced resistance: to prevent unevenness due to the storage capacitor voltage burn out the storage capacitor, because two identical electrolytic capacitors can not make it, so the voltage of each capacitor may be different, and the high withstand voltage fever is serious (capacitor equivalent series resistance) Or more pressure values ​​and injuries.

C2 capacitor;

Absorption capacity, the main role of absorbing igbt over-current and over-voltage energy.

(2) straight-paid part

Vt1 - vt6 inverter tube igbt (insulated gate bipolar power tube): The main component of the inverter circuit, the core elements of the inverter. DC inverter frequency, amplitude adjustable AC (ac).

Vt1 - vt6 freewheeling diode: The role of the heart is to return the braking process of the motor to the current DC supply channel and the inverter tube Vt1 - vt6 conduction and global alternate transformation process, providing a channel.

(3) Control section: power board, driver board, control panel (CPU)

Power board: The operation panel switches the power supply circuit. The main control board, drive circuit, detection circuit, and fan provide low-voltage power. The switching power supply low-voltage power supply provides:, plusmn; 5v, and plusmn; 15v, and plusmn; 24vCPU auxiliary circuit , control circuit, display panel to provide power, and so on.

Driver: Mainly the CPU generates the PWM pulse drive circuit to stimulate the output voltage generated by the igbt drive signal to meet the requirements.

Control Panel (CPU board): Also known as the CPU board is a person's brain, processing a variety of signals and control procedures


[Note: The dcac - and gt; inverters are a better way! Thanks to Cai Gong for commenting here. Also welcome you to our editorial team to put forward more valuable comments and suggestions!Mym(2005.08.23)]



(3) The rotational speed of the motor can be freely changed?
*1: r/min
Motor speed unit: rotations per minute, can also be expressed as RPM.
For example: 2-pole motor 50 Hz 3000 r/min
4-pole motor 50 Hz 1500r/min

The dollar motor frequency is proportional to the speed of the motor. This refers to the motor of the AC induction motor, which uses the industry's motor of this type of motor. The rotational speed of an AC induction motor (hereinafter referred to as a motor) is approximately exactly the magnetic pole and frequency of the motor. The number of cars is fixed by the working principle of the motor. Since the extreme value is not a continuous value (2 times, such as 2-2), it is generally unsuitable to adjust the speed of the motor by changing the value.
In addition, the frequency is adjusted and then supplied to a car other than a car, and the rotational speed of this motor can be controlled freely.
Therefore, controlling the frequency converter is the preferred destination device motor speed control device.
N=60f/p
Nurse: Synchronization speed
F: frequency
P: motor logarithm

$ Changing the frequency and voltage is the best motor control method. If only changing the frequency does not change the voltage, reducing the frequency of the overvoltage will cause the motor (field) to cause the motor to burn out. So while the inverter changes the frequency, it must change the voltage at the same time.
The output frequency is higher than the rated frequency and voltage but cannot continue to increase. The maximum value can only be equal to the rated voltage of the machine.
For example: In order to reduce the rotational speed of half the motor, the output frequency of the inverter changes from 50Hz to 25Hz, then need to change the output voltage of the inverter from 400v to 200v

2. When the motor speed (frequency) changes, the output torque?
*1: Power supplied by commercial frequency power grid power supply (commercial power supply)
(4) Starting current When the motor is running, the inverter output current
------------Inverter Driven Starting Torque, Maximum Torque, Direct Manual Frequency Power Excitation ------------
The motor has a great influence on the start-up and acceleration of the commercial frequency power supply. When using the inverter, the impact will be less. Starting a power supply directly can generate a large starting current. When using an inverter, the inverter output voltage and frequency are gradually added to the motor, and the motor starting current has less influence.
Generally, the frequency (speed) at which the motor torque drops is reduced. Reduce the actual data of some inverters to the instruction manual.
By using the flux vector to control the frequency converter, it will improve the engine's low-speed torque shortage, even at low-speed motors can be sufficient torque output.

(5) When the speed control of the inverter exceeds 50 Hz, the output torque of the motor will decrease.

General Motors designs and manufactures 50 Hz voltage and rated torque in this voltage range. So the rated speed is called constant torque speed. (t=tep&liver transplantation;=PE)
The output frequency of the inverter is greater than 50 Hz, and the motor's frequency is inversely proportional to the frequency.
There is a frequency speed of more than 50 Hz When the motor is running, the motor load must be considered in order to prevent the motor from outputting torque.
For example, the motor torque is generated at 100 Hz to generate a torque of 1/250 Hz.
Therefore, the rated frequency is called constant power speed. (p=question*ie)

(6) Inverter applications above 50 Hz We all know that the rated voltage and current rating of a particular motor are constant.
Ratings for frequency converters and motors: 15kw/380v/30, motor speed can exceed 50Hz when 50Hz frequency converter speed output voltage is 380v, current 30. At this time, if the output frequency is increased to 60hz, the maximum output voltage and current frequency converter is only a 380v/30. Obviously, the output power is constant. So we call it constant power speed regulation.
When the torque situation?
Because p=wt (t:w: angular speed, torque). Because p is a constant, w increases, so the force will decrease accordingly.
We can also change one point of view:
Motor stator voltage u = e + I * r (I currently, electronic resistance re induced potential)
We can see that you are the same as me and are the same.
E = k ** x, f (Kathy: constant, f: frequency, x: flux), so when from 50-f, gt; 60 Hz, x will reduce the motor accordingly, t = k * I * x (k: constant, I: current, x: flux), so the force t will follow the decrease of the magnetic flux decrease x.
At the same time, less than 50 Hz, u * f = e / f is constant in the constant flux (x) because I * r is small. Torque t is directly proportional to the current. This is why the converter flow capability often describes the ability to overload (torque). And is called constant torque speed (nominal current, and gt; maximum torque constant)
Conclusion: When the inverter output frequency increases to more than 50 Hz, the output torque of the motor will decrease.
(7) Other factors related to the output torque heating and cooling function of the inverter output current capacity, affecting the inverter output maximum torque.
Carrier Frequency of General-purpose Inverter: The highest rated current carrier frequency of the object, and the maximum ambient temperature can ensure continuous output value. By reducing the carrier frequency, the motor current will not be affected. But reduce heating components.
???Boundary temperature: Do not like because it is found at a relatively low temperature to increase the current value of the inverter protection.
Height: The height increases and the thermal insulation performance has an effect. Generally less than 1000 meters can not be considered. Every 1000 meters, more than 5% is enough.
(8) How does vector control improve the output torque of a motor?
*1: Increase torque This function increases the inverter output voltage (mainly low frequency) to compensate for the torque loss caused by the stator resistance voltage drop and increase the output torque of the machine.
U.S. dollar technology improves the output torque of low-speed motors. "Vector control," can make the motor output at low speed, for example (without speed sensor) 1 Hz (4-pole motor, about 30r/min) Torque is output at 50Hz power (up to approximately 150% of rated torque).
The voltage drop of the conventional v/f control motor is relatively increased with the loss rate of the motor, which results in a lack of excitation so that the motor cannot obtain sufficient rotational force. In order to make up for the shortage, it is necessary to compensate for the voltage drop caused by increasing the voltage of the inverter and decelerating the motor. When the function of the inverter is called, "The torque increases," (*1).
The torque increase function is to increase the output voltage of the inverter. Even if the output voltage is increased, the motor torque cannot be increased accordingly. Because the current motor torque component contains the motor and other components (such as excitation components).
And "Vector control," the distribution of the motor's current value, which produces the torque of the car's current components and other current components, such as field component values.
And "Vector control," can be optimized through the response of the voltage drop of the motor, allowing the motor to output torque without increasing the current situation. This feature also effectively increases the temperature rise of the motor at low speeds.
Basic knowledge of inverter
1. Inverter-based
1: Variable frequency speed control variable frequency conversion, meaning the change of voltage and frequency, which is called variable voltage frequency conversion.

2: CVCF constant voltage, constant frequency, constant voltage and constant frequency, which is called constant voltage constant frequency.

The power we use is divided into alternating current power and direct current power. Most of the direct current power is generally through an alternating current power transformer and is rectified and filtered. The power of people using AC power always uses about 95% of the power supply.

Home or for factories, single-phase AC power supply, three-phase AC power supply, voltage and frequency according to national regulations have certain standards, regulations in mainland China, direct users single-phase 220v AC (ac), three-phase AC voltage is 380 V, 50 Hz, other countries supply voltage and frequency may vary in voltage and frequency in our country, such as single-phase 100v/60 Hz, three-phase 200v/60 Hz, etc., standard AC mains voltage and frequency of AC power Frequency of.

In general, a device in which the voltage and frequency of a fixed-frequency AC is converted to a voltage or frequency-variable AC (ac) is called a "converter".

In order to generate a variable voltage and frequency, the device must first convert the source AC to DC, and this process is called rectification.
The equipment that converts dc to alternating current (ac), the scientific term "makes" (inverter).
The universal inverter DC power supply is reversed to a fixed frequency and voltage inverter power supply. Inverters with adjustable frequency inverters and adjustable voltages are called inverters.

Xi'an Motor Factory

Sine wave inverter output waveform simulation, mainly used for three-phase asynchronous motor drive, also known as frequency converter.
It is mainly used for the high demand of the frequency conversion inverter waveform of instrument test equipment. The wave arrangement can output standard sine wave and variable frequency power supply. The price of a universal inverter power inverter is 15-20 times.

Since the main device for changing the voltage or frequency of the inverter device is called "makes", the product itself is named "makes", ie. The inverter inverter can also be used for household appliances. Household appliances that use frequency converters include not only an electric motor (such as air conditioners) but also fluorescent lamps and other products.

The frequency converter controls the motor, can change the voltage, can change the frequency. However, most of the inverters used in fluorescent lamps are used to adjust the frequency of the power supply.


The working principle of the inverter is widely used in various fields. The power source of the computer power supply, for example, in the application program, the frequency converter is used to suppress the reverse voltage, frequency, power fluctuations and power moments.
Why (9) The rotation speed of the motor can be freely changed?
N=60f/p(1)N: motor speed f: frequency p: motor pole pair s: motor

Motor speed = 60 (in seconds) * Frequency (Hz) / Motor pole pair - Sliding

Motor speed unit: rotation per minute, rpm can be expressed as RPM

The speed of the motor is proportional to the slip frequency of the synchronous motor torque is 0, synchronous motor speed = 60 (in seconds) * frequency (Hz) / motor pole pairs

The asynchronous speed is lower than the speed of the synchronous motor.

For example: Step 4 Three-phase motor 60 Hz Less than 1800r/min 4-pole 50 Hz three-phase asynchronous motor is less than 1500r/min
This article refers to the motor of the AC induction motor, and the motor of the industrial field using this type of motor.
The rotational speed of an AC induction motor (hereinafter referred to as a motor) is approximately exactly at the pole pair number and frequency of the motor.
The logarithm is fixed by the motor's working principle of the motor poles. Since the logarithm of the motor pole logarithm is equal to 2, the number of motors is not a continuous value (2 times, such as 2-2), so the motor speed is not adjusted by the discomfort and the changed value.
In addition, the motor power frequency, so that the value outside the car can be adjusted, and then supply the motor, the motor speed can be controlled freely.
Therefore, the purpose of controlling the frequency converter is to select the motor speed control device.
(10) Changing the frequency and voltage is the best motor control method If only the frequency is changed, the motor will be burned. Especially when the frequency decreases, this problem is very prominent. In order to prevent engine combustion accidents, the inverter must change the voltage at the same time while changing the frequency.

For example: In order to reduce the rotational speed of half the electric motor, the output frequency of the inverter must change from 60 Hertz to 30hz, then must change the output voltage of the inverter from 400v to 200v.

If you want to use the correct inverter, it is necessary to seriously consider the heat dissipation problem.

Inverter failure rate increases with temperature and exponentially. The service life index decreases with temperature. The ambient temperature is 10 degrees and half the service life of the converter. Therefore, we should attach great importance to the cooling problem!

The current inverter work through the inverter is very large, the heat generated by the inverter is also very large, can not ignore the impact of heat

Typically, the sensor is mounted in a control cabinet. We need to know what the thermal value of the drive is. You can use the following formula to estimate:

Calorific value=approximate (in kilowatts) of inverter capacity, times; 55[w] Here, if constant torque load is the inverter capacity (flow 150%*60s) if the inverter DC or AC reactor, reactor? Also in the cabinet, the heat will be greater. It is better to have a reactor installed on it or a converter.

This time can be used to estimate: Inverter capacity (kW), times; 60 [w], because the inverter hardware manufacturers are similar, so each brand type. Note: If there is a braking resistor, because the braking resistor has a lot of heat, it is best to install the location and the best inverter is isolated, such as on the shelf or beside.

(11), then, howtoadoptcanlowercalorificvalueincontrolcabinet?

Whentheinverterinstalledinthecontrolcabinet,wanttoconsidertheproblemoffrequencyconvertercalorificvalue.

Theincreaseofvalueaccordingtotheheatinsidethecabinet, toappropriatelyincreasethesizeofthecabinets.Therefore, toreducethesizeofthecontrolcabinetasfaraspossible, itisnecessarytomakethecabinetasmuchaspossibletoreducetheheatinvalue.

Ifinstalledinfrequencyconverter, theconverterradiatorpartsontheoutsideofthecontrolcabinet,willmakethefrequencyconverterhas70%oftheheatreleasedtotheoutsideofthecontrolcabinet.Duetothelargecapacityinverterhasagreatdealofheat,soforlargecapacityinverterismoreeffective.

Youcanalsouseisolationplateseparatesontologyandradiator,radiatorcoolingdoesnotaffecttheinverterontology.Thiseffectisverygoodalso.

Theinverterinthedesignofheatdissipationisbasedonverticalinstallation,acrossthecoolingwillbeworse!
Ab0utthecoolingfan(12)
Generalpowerslightlybiggerfrequencyconverter, withcoolingfan.Atthesametime,alsosuggestedthatinthecontroloncoolingfanoutletinstallation.Airinlettoaddmeshtopreventdustfromenteringthecontrolcabinet.Awareofthecontrollerandfrequencyconverterfanare,notwhosubstitute.Otherquestionsab0uttheheatdissipation

1, atanaltitudeofover1000m,becausetheairdensityisreduced,soshouldincreasethecoolingairvolumeofthecabinetinordertoimprovethecoolingeffect.Theoreticallytheinverteralsoshouldconsidercapacity,1000mper-5%.Butactuallybecauseofthedesignontheinverterloadcapacityandheatcapacityisbiggerthanactualusedcommonly,soalsodependsonthespecificapplication.Forexample,inthe1500m,buttheperiodicload,suchaselevators,therewouldbenoneedtodrop.

2, switchfrequency: fevermainlycomesfromtheigbtinverter, igbtfeverhavefocusedonandoffinstantly.Sohighswitchfrequencywhentheororificvalueofnaturalfrequencyconverter.Somemanufacturerthatcanreducetheswitchingfrequencyexpansion,itisforthisreason.

Vectorcontrolishowtomakethemotorwithlargetorque
(13)torque
Thisfunctionincreasetheinverteroutputvoltage,andtheoutputtorqueofthemotortomaketherelationshipisdirectlyproportionaltothesquareofthevoltageincrease,toimprovetheoutputtorqueofthemachine.Toimprovethetechnologybythelackofthemotoroutputtorquelowspeed

Use&quot;Vectorcontrol&quot;,canmakethemotoratlowspeed,suchas(withoutspeedsensor)1hz(for4polemotor,thespeedofab0ut30r/min)theoutputtorqueofthemotorcanbeachievedin50hzpowersupplyoutputtorque(mostab0ut150%oftheratedtorque).

Forconventionalv/fcontrol,motorofthevoltagedropwiththelossofthemotorspeedandrelativelyincreased,thisleadstotheshortageofexcitationandmakethemotorcan'tgetenoughrotatingforce.Tocompensatefortheshortage,requirebyraisingthevoltagefrequencyconverter,motorcausedbythereducedspeedtocompensateforvoltagedrop.Theinverterofthefunctioniscalled"ascension"torque.

Torqueincreasefunctionistoincreasetheoutputvoltageofinverter.Yetevenraisealotofoutputvoltage, themotortorquecannotanditscurrentcorrespondingincrease.Becausethemotortorquecomponentofcurrentcontainsthemotorandothercomponents(suchasexcitationcomponent).

Thevectorcontrolofthemotorcurrentvalue, soastodeterminethetorqueofthemotorcurrentcomponentandothercurrentcomponent,suchasexcitationcomponentvalues.&quot;Vectorcontrol&quot;Canpassontheresofthemotorofthevoltagedrop, optimizingcompensation,withoutanyincreaseinthecurrentcircumstances,toallowthemotoroutputtorque.Thisfeatureisalsoeffectivetoimprovelowspeedwhenthetemperatureriseofthemotor.
(14) inverterbrakingcondition
1:theconceptofthebrake

Referstothepowerfromthemotorsideflowtotheinverterside(orthepowersupplyside),thenthespeedofthemotorishigherthanthesynchronousspeed.

Loadenergyintokineticenergyandpotentialenergy.Kineticenergy(bythespeedandweighttodetermineitssize)accumulationwiththemovementofobjects.Whenthekineticenergyisreducedtozero,thethingisinstopstate.

Cima Motor

Themethodofmechanicalbrakedeviceistheobjectwithbrakekineticenergyconversion??frictionandcanconsume.

Fortheinverter, iftheoutputfrequencyisreduced,frequencyalsoreducethemotorspeedwillfollow.Thenwillproducebrakingprocess.Thepowergeneratedbythebrakewillreturntotheinverterside.Thepowercanuseresistanceheatconsumption.

Classloadinascension, thefalls, energy(potentialenergy)willreturntotheinverter(orpower),carriesonthebrake.

Theoperationmethodiscalled"regenerativebraking",andthismethodcanbeappliedtotheinverterbraking.

Duringdeceleration, theconsumptionofthepowerifnotoverheatmethodconsume,butreturnedtotheenergymethodofinverterpowersourcesideiscalledcalled "powerreturnregenerationmethod".Inpractice,theapplicationneedstobe"energyfeedbackunit"option.

Howtoimprovethebrakingability(15)?

Inordertouseheattoconsumptionofrenewablepower,needtoinstallbrakingresistorintheinverterside.

Inordertoimprovethebrakingcapacity,shouldnotexpectconverterbyincreasingthecapacitytosolveproblems.Pleasechoose"brakingresistance","brakeunit"or"renewablepowerconverter"andotheroptionstoimprovetheinverterbrakingcapacity.

(16) whenthemotorrotationspeedchange, theoutputtorque?

Theinverterdrivestartingtorqueandmaximumtorquethanthedirectlaborfrequencyfrequencypowerdrivewhenstartingtorqueandmaximumtorque.

Weoftenhearab0utthefollowingstatement: "themotorinthepowersupply, powerfrequencyofstartingandacceleratingtheimpactisverybig, andwhentouse ??? frequencycounterpowersupply, theimpactwillbeless" .Ifwithlargevoltageandfrequencyofthestartermotor, makedirectlaborfrequencypowergridpowersupply, forexample, canproducealargestartingshock (largestartingcurrent) .Andwhenusingtheinverter, theinverteroutputvoltageandfrequencyisgraduallyaddedtothemotor, sothemotortorquelessthanthetorqueva1ueofthepowerfrequencypowersupply.Sotheinverterdrivenmotorstartingcurrentissmall.

Usually, motor???torquetoreducewiththedecreaseofthefrequency(speed)toreducetheactualdatainsomefrequencyconverterwillgiveinstructionsinthemanual.

Throughtheuseofmagneticfluxvectorcontrolfrequencyconverter,willimprovethemotoratlowspeedtorquewheninsufficient,eveninthelowspeedmotorcanalsobeenoughtorqueoutput.

Whentheinverterspeedcontrolto20%greaterthantheratedfrequency,theoutputtorqueofmotorwillbereduced

Generalmotorsisinaccordancewiththedesignandmanufactureofratedfrequencyvoltage,theratedtorqueisalsogiveninthisvoltagerange.Sounderratedfrequencycontrolofmotorspeed??forconstanttorquespeed.(t=tep&lt;=PE)inverteroutputfrequencyisgreaterthanthertherfrequencyfrequency50Hz) (suchasourcountry'smotor, motorandtorquetothelinearrelationshipoffrequencyisinverselyproportionaltodrop.

Whenthemotorisrunning,withgreaterthan20%ratedfrequencyspeedmotorload??smallmustgiveconsideration,inordertopreventthemotoroutputtorque.

Forexample,ratedfrequency50hzmotortorquegeneratedina100hztoreducetoab0ut50hzofthetorqueareproducedwhenthe1/2.Soabovetheratedfrequencyspeedregulationiscalledconstantpowerspeed.(p=ue*ie)



Frequencyconversioniscansaveelectricity?

Answer: ifthefrequencyofthefundamentalfrequencyis50hz, sobelow50hzistheconstanttorquerunning ,, thatis, theoutputtorqueiscertain, asthefrequency, theoutputspeedalsofell, musthavetheoutputtorque, outputpowerdecreases, andso, theinvertercansaveelectricity, and, therefore, onthe22kwmotorandbelow50basebandfrequencyofvariablefrequencymotoroutputtorqueisthesame, t = 9550p / n, tfortheoutputtorque, p ?? power, nfortheoutputrotationalspeed, and, ifthefrequencyishigherthanthefundamentalfrequency50hz, theoutputpowermustbe, Torquewillbesmaller

Constantpowerandconstanttorque(17)?

Withspeedloopandvoltageloopandcurrentloopofadependentexcitationdcmotorspeedcontrolsystemoftwokindsofrunningcondition.

Whenaconstantmagneticfieldandthearmaturecurrentisconstant,bychangingthearmaturevoltagecontrol,fortheconstanttorquespeedregulation,thertherconditionofconstanttorqueoperation.

Abovethebaserate, intotheweakmagneticacc, thearmaturevoltageconstant, speedregulationbychangingmagneticfield, fortheconstantpowerspeedregulation.Atthistimeoftherunningcondition,fortheconstantpoweroperation.

Understanding andmisunderstanding:

Saidseparatelyexciteddcmotorunderthebasespeedisconstanttorqueoperation,itisaprerequisite,thearmaturecurrentisconstant,constanttothearmaturecurrent,mustbeacurrentloopcontrolsystem,weknowthatdcmotortorqueproportionaltothearmaturecurrentexcitationcurrentoftheproduct,howcanwithoutcurrentlooparmaturecurrentconstant,imagineaseparatelyexcitedmotor,themagnetic,totalpressurestarting,armaturecurrentcanreachseveraltimesorevenmore,howcanisaconstanttorque?

Bythesametoken, the "abovethebasespeedisconstantpoweroperation"isalsoaprerequisitefor,

Thearmaturecurrentisconstant, thearmaturevoltageconstant, power(andthereforeisaconstant)

Complementtoanswer:

Havenotused6ra70, nomatterwhattypeofsystem, aslongasitiswithaspeedloop, thevoltageloopandcurrentloopofadependentexcitationdcmotorspeedcontrolsystemisthesprinciple.



Whatisthemotorcapacity,frequencyconvertercapacity?Howtocalculate?

Isthemotorratedpower, thepowerratingoftheinverterinkw.Thenameplatehave,youlookcloselytosee.



Howfrequencyconverterselection?

Howfrequencyconverterselection?
Frequencyconverterselectionisveryimp0rtant, iftheselectionisnotreasonable, causedthelossofmoneyandtime,lightweight, productionaccident,damage.
Theinverterchoiceshouldconsiderthefollowingaspects:
(18)invertertypeselection
Invertercanbedividedintogeneralandspecial,generallyrequirehighmechanicalloadandoverloadcondition,selectionofgeneralinverter.Canbedividedintothepumpspecial,specialelevatorspecialinverter,tensioncontrol,special,etc.Tochooseaccordingtotheirownapplicationenvironment.
(19)invertercapacitytochoose
Frequencyconvertercapacityisoneofthemostimp0rtantchoice,startfromtheactualloadcurrent,loadtorque,reasonablecontrolmodetochoose.Ifloadisfan,waterpump,pumpspecialandmotorwithpower;Rootsblowerandpumpshouldchoosepumpspecialonegreaterthanthemotorpowerinverter.Optionsstarttorqueiseasytooverlook,thebiginertiaload,invertermightbebetterthanmotorpowerincreasethenumberoffiles.Ifyouhaveanyquestions,[email protected]
(20)invertercost-effectivechoice
Anyoneinverterpriceisguess.Hereisnotmuchsaid,don'tlookatads,toseewhetherthetherapy???.
(21)inverterafter-salesserviceselection
After-salesserviceisthekeytochoosethebrandoffrequencyconverter,imp0rtedbrandwithreliablequality,highprice,goodafter-salesservice,butafterwarranty,maintenanceofpricehighveryhigh.Homebredbrandqualitygoodandbadareintermingled,hasgoodqualityandimp0rtedbrand,thelowqualityisbadtosaid.Goodafter-salesservice,evenbeyondthewarrantyperiod,maintenanceandpriceisreasonable.[/size][/size]



Why(22)ofthemotorrotationspeedcanbefreetochange

N = 60f / p, n: synchronousspeed, f: ??? thesourcefrequency, p: thenumberofmotor, changethefrequencyandvoltageistheoptimalmethodofmotorcontrol.Ifonlychangethefrequency, themotorwillbeburnout.Especiallywhenthefrequencydecreases, theissueisveryoutstanding.Inordertopreventmotorburnaccidents, inverterinthechangefrequencyatthesametime, mustwanttochangethevoltageatthesametime, forexample, inordertohalvetherotationspeedofthemotor, theinverteroutputfrequencymustchangefrom60hzto30hz, theinverteroutputvoltageisthenmustchangefrom200vto100v.Forexample: inordertohalvetherotationspeedofthemotor, theinverteroutputfrequency ??mustchangefrom60hzto30hz, theinverteroutputvoltageisthenmustchangefrom200vto100v.



Theissuesoftheinverterbraking(23)

(1) theconceptofbraking: referstothepowerfromthemotorsideflowtotheinverterside (orthepowersupplyside), thenthespeedofthemotorishigherthanthesynchronousspeed.Loadenergyintokineticenergyandpotentialenergy.Kineticenergy (bythespeedandweighttodetermineitssize) accumulationwiththemovementofobjects.Whenthekineticenergyisreducedtozero, thethingisinstopstate.Themethodofmechanicalbrakedeviceistheobjectwithbrakekineticenergyisconvertedtothefrictionandcanconsume.Fortheinverter, iftheoutputfrequencyisreduced, frequencyalsoreducethemotorspeedwillfollow.Thenwillproducebrakingprocess.Thepowergeneratedbythebrakewillreturntotheinverterside.Thepowercanuseresistanceheatconsumption.Classloadinascension, thefalls, energy (potentialenergy) willreturntotheinverter (orpower) ,brake.Theoperationmethodiscalled&quot;Regenerativebraking&quot;,andthismethodcanbeappliedtoinverterbraking.Duringdeceleration,theconsumptionofthepowerifnotoverheatmethodconsume,butreturnedthetheenergymethodofinverterpowersourcesideiscalled&quot;Powerret Urnregenerationmethod&quot;.Inpractice,theapplicationneeds&quot;Energyfeedbackunit&quot;Option.

(2) howtoimprovethebrakingcapacity?

DC

Inordertouseheattoconsumptionofrenewablepower,needtoinstallbrakingresistorintheinverterside.Inordertoimprovethebrakingcapacity,shouldnotexpectconverterbyincreasingthecapacitytosolveproblems.Pleasechoose&quot;Brakingresistor&quot;,&quot;Thebrakingunit&quot;Or&quot;Renewablepowerconverter&quot;Suchasoptionstoimprovetheinverterbrakingcapacity



(24) vectorcontrolishowtoimprovingthecapabilityoftheoutputtorqueofthemotor?

*1:enhancingthetorque

Thisfunctionincreasetheinverteroutputvoltage(mainlylowfrequency),tocompensateforthestatorresistancevoltagedropcausedbythetorqueloss,improvetheoutputtorqueofthemachine.

$technologyimprovethemotoroutputtorqueatlowspeed

Use&quot;Thevectorcontrol??&quot;,canmakethemotoratlowspeed,suchas(withoutspeedsensor)1hz(for4polemotor,thespeedofab0ut30r/min)theoutputtorqueofthemotorcanbeachievedin50hzpowersupplyoutputtorque(mostab0ut150%oftheratedtorque).

Forconventionalv/fcontrol, motorofthevoltagedropwiththelossofthemotorspeedandrelativelyincreased,thisleadstotheshortageofexcitationandmakethemotorcan'tgetenoughrotatingforce.Tocompensatefortheshortage, requirebyraisingthevoltagefrequencyconverter,motorcausedbythereducedspeedtocompensateforvoltagedrop.Frequencyconverterofthefunctioniscalled&quot;Torqueincrease&quot;(*1).

Torqueincreasefunctionistoincreasetheoutputvoltageofinverter.However,evenifalotofoutputelectric???,doesnotthemotortorqueanditscurrentcorrespondingincrease.Becausethemotortorquecomponentofcurrentcontainsthemotorandothercomponents(suchasexcitationcomponent).

&quot;Vectorcontrol&quot;Distributionofthecurrentvalueofthemotor,soastodeterminethetorqueofthemotorcurrentcomponentandothercurrentcomponent,suchasexcitationcomponentvalues.

&quot;Thevectorcontrol???&quot;Canpassontheresofthemotorofthevoltagedrop,optimizethecompensation,theincreaseincurrent,allowingthemotoroutputtorque.Thisfeatureisalsoeffectivetoimprovelowspeedwhenthetemperatureriseofthemotor.

Three-phase asynchronous motor summary â–¼ reproduced