Electric machinery serves coefficient National Electrical Manufacturers Association of United States of one word out (NEMA) write publish ” MG1-2009 electromotor and dynamo part ” standard, common calls NEMA MG1 the standard. The service coefficient that this standard elaborated AC motor in detail (Service Factor, or say to use coefficient, abbreviation S.F) the application that goes up in AC motor with service coefficient, its are main content is: The service coefficient of AC motor is a multiplicator. Multiply when it on when rated power, susceptive power load allows below the requirement that expresses to serving coefficient to set.
In normally use condition falls, move continuously by rated load. When voltage and frequency maintain the regulation on nameplate to be worth, electromotor but overload is multiplied to rated power on the service coefficient on nameplate. Electromotor is in any is more than the service of 1 moves below coefficient, factor of its efficiency, power and rotate speed can be different from the numerical value below rated load condition, but locked-rotor torsion and electric current and the biggest torsion will be maintained changeless. Electromotor is in any is more than when the service of 1 moves continuously below coefficient, will decrease anticipate service life. With by rated nameplate power next moving photographs are compared, insulation life and bearing life will decrease.
In addition still gave out to serve coefficient to be the 1.15 electromotor that reach above, when moving below the load that serves coefficient, the regulation that its temperature rise is worth: Insulation is 70 ℃ when grade class A; Insulation grade is 90 ℃ when B class; Insulation grade is 115 ℃ when F class, when if use F class to be isolated from,pointing out, answer to be mixed to bearing temperature lubricant etc give special consideration. Above is the coefficient of electric machinery service that NEMA standard place speaks of.
Tell popularly, the biggest load that coefficient of electric machinery service expresses to allow electric machinery to work for a long time continuously is led, it is to measure electric machinery a parameter of ability of successive and laden job. It is for field of contented and special application close or spare overload leads duty style, the ratio of power of permission the biggest output and rated power is on numerical value, duty type is operation pattern, do not answer with ability coefficient promiscuous together.
Be like: Power is the electric machinery of 30kW, if serve coefficient for 1.15, so its can output actually most high-power is 30×1.15=34.5kW.
Today, we discuss duty type and service coefficient, unscramble service coefficient through a few example, aim to coach electric machinery design is mixed reasonable use electric machinery.
Pneumatics Electromechanical machine serves coefficient example to unscramble
Electric machinery is common periodic duty of S7 of ～ of the duty when duty type has S1 successive duty, S2 weak point, S3, the successive periodic duty that not common gearshift having S8 becomes laden and S9 load, rotate speed is aperiodic sexual change duty. When operation pattern and duty of S9 of ～ of standard mode S1 medium any a kind not be identical, if ask electric machinery changes,bear moves continuously, can use “S1 successive duty + function of electric machinery of the combination tie such as service coefficient ” , token. Although “ duty + combination of service coefficient ” is a kind of duty type really actually, but cannot saying to serve coefficient however is duty type.
Serving coefficient is an integrated index, the biggest overload is equal to to lead on numerical value. According to the moving character of three-phase asynchronous electromotor, service coefficient size sets commonly for 1.15-1.25, because use the service coefficient of on the low side, do not have the applied efficiency of materiality actually; Serve coefficient on the high side, sex of aid of electric accident go by is not ideal.
It is with screw pneumatics machine exemple, the size of electromotor load shows periodic change, it changes to the demand of tolerance as the person that use, when the highest actuating pressure that achieved set of place of the person that use pneumatics machine begins to uninstall, machine of the pneumatics when the lowermost actuating pressure of set of place of the person that drop to use when the actuating pressure that manages a network is automatic to load.
The power of electromotor chooses even if make electromotor is in commonly below anticipated negative charge when the job efficiency factor of highest, power is bigger. But the axial power of electromotor at the same time must can full load moves, get used to the operating condition that overload of guest householder time runs namely. Normally, the choice of power of the electromotor when full load moves is to anticipate economy runs axial power to multiply on 1.1 times.
If use the 1.1 times “ that anticipates economy runs axial power to chose electromotor power to do not have our place to say to serve coefficient ” directly, the efficiency that is electromotor if really ever since and power factor compare on the low side, create the waste of the sources of energy and cost respect. Accordingly, ” of “ service coefficient is actual it is to ensure pneumatics aircraft is efficient the important parameter that economy runs.
Express 1 be 2 extremely coefficient of 15kW, IP23, service the actual measurement parameter of 1.15 electric machinery.
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From inside the watch data can see, what Dou Youming of temperature of stator winding temperature rise, bearing, housing temperature shows is elevatory. The test has according to standard electric machinery only when some electric machinery manufacturer do type to experiment, cannot the function index that accurate judgement electric machinery leaves in state of other service coefficient.
” of coefficient of service of electric machinery of “ of pneumatics machine industry goes regular
At present electric machinery of so called “ serves industry of Chinese pneumatics machine coefficient ” , it deviated from already completely actually the criterion of NEMA, it is the electric machinery that rated power is 110kW originally for instance, write into rated power 90kW on electric machinery nameplate, s.F mark is 1.2 or 1.25. Want possibly to the personage outside the industry to be illogical, is high-power electric machinery sells when small-power lose money in business? See 110kW compare 90kW power big 20kW from paper face actually, in aircrew input samer than power situation falls (it is 1 class likewise can effect) , of course the empty press of 90kW is energy-saving.
The GB19153-2009 that is about to carry out formally on July 1 this year ” cubage type air compresses value of functional effect demarcate to reach can effect grade ” standard, provided test value of power input of unit of circumgyrate pneumatics airplane, should be less than the value of big first gear of drive electromotor rated power. For instance 90kW of electromotor rated power, its are in when rated platoon runs pneumatics machine below baric force, aircrew power input must not exceed 110kW, this goes up from fountainhead keep within limits what electric machinery serves coefficient is malign expand. At the same time to obtain lesser aircrew power input (cooling fan electric machinery considers even for machine of cold to wind pneumatics) , need to use efficient motor. Especially machine of frequency conversion pneumatics, to satisfy cubage discharge 40% when can obtain better can effect index, that is to say electromotor is when low rotate speed electric machinery efficiency is very tall still, this uses electric machinery of permanent magnetism synchronism or the motor that have same effect with respect to need.
Anyhow, the “ that use and uses good motor serves coefficient ” , square but will empty press kind device control character is in of the regulation, move inside reasonable range. Otherwise, the initiative design of electric machinery is met necessarily deviate is actual bear state, electric machinery efficiency or cannot get sufficient play or cannot be competent ” of ” full load moves for a long time continuously.
Reference material
Efficient electric machinery gets the person that run, ” standard of new edition GB19153 is about to release, machine of cubage type pneumatics is energy-saving the “ that decrease a platoon more ground connection enrages ” " , 2019.11.27