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About China's inverter test requirements or technical standards

Aug 18, 2020

About China's inverter test requirements or technical standards

China National Power Electronics Standardization Technical Committee for Speed Control of Electric Drive Systems Semiconductor Power Converters was established in 2000 under the situation of rapid development of electric drive speed control products at home and abroad. The secretariat is affiliated with Tianjin Electric Drive Design Institute. Responsible for the organization and management of standardization technical work in the technical field of the national electric drive speed control system. The products involved are mainly AC and DC electric drive equipment for the basic industries of the national economy. Six national and industry standards for electric drive speed control systems have been formulated: GB/T3886.1-2002, JB/T10251-2001, GB/T12668.1-2003, GB/T12668.2-2003, GB12668.3- 2004, GB/T12668.4.


Starting from the quality control of the entire product process, the corresponding speed control device test methods, speed control device environmental conditions regulations, speed control device technical conditions, speed control device acceptance regulations, speed control device safety regulations and other supporting standards will be formulated in Gradual implementation during 2005-2007.

                

   At present, China is paying great attention to China's national compulsory product certification (3C certification), which is based on China's national standards and technical rules. China announced the first batch of mandatory product certification catalogs, including 19 categories and 132 products.


1. Scope of application of GB/T12668.2 standard

                    

"GB/T12668.2-2003 Adjustable Speed Electric Drive System Part 2: General Requirements-Regulations on the Rating of Low Voltage AC Variable Frequency Electric Drive System" is suitable for general purpose AC adjustable speed drive systems (see Figure 1), which consists of Power equipment (including converter parts, AC motors and other equipment, but not limited to feeder parts) and control equipment (including switch control-such as on/off control, voltage, frequency or current control, trigger system, protection, status monitoring , Communication, testing, diagnosis, production process interface/port, etc.). This standard does not apply to traction drives and electric vehicle drives; it is applicable to electrical drive systems connected to AC power supply voltages below 1kV, 50Hz or 60Hz, and load-side frequency up to 600Hz. This standard gives performance requirements for inverter ratings, normal use conditions, overload conditions, surge capacity, stability, protection, AC power grounding and testing.


This article introduces the parameter ratings and test requirements of related low-voltage inverters.


2. Inverter function characteristics

                

  Inverter should have some specified characteristics, which may include (but not limited to) one or more of the following:

     Timing acceleration;

     Timed deceleration;

     jog;

     Adjustable current limit;

      Dynamic braking;

     Reverse;

     Regeneration (braking);

     Power grid filtering;

     Input/output data processing (analog/digital);

     Automatically restart;

     (torque) increase;

     DC braking;

     Pre-charge circuit.

                    

   The frequency converter shall be equipped with the specified fault indication, which can be composed of two parts, the public alarm and/or the trip signal provided by the dry relay or the solid state relay. The fault indication usually acts due to one or more faults. The faults include (but are not limited to) the following:

     External failure;

     The output power part is faulty;

     Instantaneous overcurrent;

     Overheating (converter);

     No cooling air;

     Motor overload;

     Auxiliary power supply failure;

     Power supply overvoltage/undervoltage;

     Power supply lack phase;

     Internal control system failure;

   Regulator/power circuit diagnosis.

                    

  The frequency converter shall have the status indication signal of "drive on" (whether it is rotating or stopping); it can also have the status indication signal of "drive ready".

3. Conditions of use of inverter

               

  3.1 Electrical operating conditions

                    

The frequency change, voltage change, voltage unbalance, power supply impedance, power supply harmonics and some abnormal conditions should be considered: For example, the frequency is fLN±2%; the change limit of the rated input voltage is ±10%; the power supply voltage unbalance is not It should be able to operate if it exceeds 3% of the rated input voltage (ULN1) of the fundamental wave.


3.2 Environmental conditions

                    

Mainly include the use of climatic conditions and mechanical installation conditions: such as ambient temperature +5 °C ~ +40 °C; the frequency converter should be installed on a solid indoor base, ventilation or cooling in the installation area or additional enclosure The system will not cause serious impact. Abnormal environmental conditions, such as exposure to excessive dust, altitude >1000 m, etc., require specially selected structures or protective components.


3.3 Inverter storage

                    

   If the transport packaging box is not suitable for outdoor or unprotected storage, after receiving the inverter, it should be immediately placed in a place that can meet the storage requirements.

                

   Inverter storage should avoid rain, snow, freezing rain, corrosive materials, etc., and should not be stored in places above 3000m above sea level, and the total storage time should not exceed 6 months.


3.4 Inverter transportation

                    

  The inverter should be able to be transported in the supplier's standard packing box, and the ambient temperature: -25 °C ~ +70 °C. Abnormal weather conditions,

                    

   If the transportation temperature is lower than -25°C, heating transportation or other methods should be used. The shock and vibration environment cannot exceed the specified limits.


4. Inverter rating

 

  4.1 Input rating

               

   Voltage; the manufacturer should state the input rating of the inverter, the preferred value is:

  

  A) 100, 110, 200, 220, 230, 240, 380, 400, 415, 440, 500, 660, 690V, for 50Hz;


b) 100, 115, 120, 200, 208, 220, 230, 240, 400, 440, 460, 480, 575, 600V for 60Hz.


Rated input current IVN value;

     Frequency;

     Phase;

     The minimum power supply impedance (or the maximum expected short-circuit current) and the maximum power supply impedance.


4.2 Output rating

                

   Maximum rated output voltage;

   rated continuous current;

     Overload capacity (overload capacity applies to the rated speed range);

     Frequency Range;

     Phase;

     rated power;

     Output phase sequence.


4.3 Operating frequency range


The manufacturer shall use the following parameters to give the operating frequency range when the inverter can maintain its specified steady-state output current:

                  fmin = minimum frequency;

                  f0 = fundamental frequency;

                  fmax = maximum frequency.


4.4 Efficiency and loss

                    

  The manufacturer shall give the loss or efficiency under rated load and basic speed.


5. Inverter test

                

  5.1 Test type

                    

   Test types include type test, factory test, sampling test, selection (special) test, workshop test, acceptance test, field commissioning test, and witness test.


1) Type test A test performed on one or several parts manufactured according to a certain design to show that the design meets specific technical requirements


2) Factory test A test performed on each component during or after manufacturing to determine whether it meets a certain criterion.


3) Sampling test A test conducted on some parts randomly selected from a batch of products.


4) Selection (special) test In addition to the type test and the factory test, the test is carried out in accordance with the intention of the manufacturer or after consultation between the manufacturer and the user or its agent.


5) Workshop test In order to verify the design, the test of components or equipment in the laboratory of the manufacturer.


6) Acceptance test The test specified in the contract to prove to the user that the component meets certain conditions in its technical specifications


7) On-site commissioning test A test performed on components or equipment on site to verify the correctness of installation and operation


8) Witness test Any of the above tests conducted in the presence of customers, users or their agents.


5.2 Inverter standard test


The standard test items of the frequency converter are shown in the following table:


The purpose of the insulation test is to check the insulation condition of the inverter. In order to prevent unnecessary damage, the insulation resistance of the tested part can be measured with a 1000V megohmmeter before the test. In the case of an ambient temperature of 20±5°C and a relative humidity of 90%, its value should not be less than 1MW, but the measured insulation resistance is only used as a reference for the withstand voltage test and is not for assessment.


The purpose of light load and function test is to verify whether all parts of the inverter's electrical circuit and the cooling system are connected correctly, whether they can operate normally with the main circuit, and whether the static characteristics of the equipment can meet the specified requirements. When this test is taken as a factory test, the inverter will only run under the rated input voltage, while in the type test, the function of the equipment should be tested at the maximum and minimum rated voltage.


The rated current test is to check whether the inverter can operate satisfactorily under the rated current.


The over-current capability test is a part of the load test. It is to apply a specified short-term over-current value at a specified time interval under the rated operation condition, and the inverter can work normally.

The measurement of ripple voltage and current is carried out when the user or his agent requests it, and is carried out in accordance with the provisions of GB/T3859.2 electrical test methods and product classification standards.

The power loss can be calculated on the basis of measurement, or directly measured. The power loss of the indirect cooling converter can be calculated from the measured heat transferred by the heat transfer medium (using the heating method) and the estimated heat flow through the inverter housing.


The purpose of the temperature rise test is to determine whether the temperature rise of each component exceeds the specified limit temperature rise when the inverter is running under rated conditions. The test shall be carried out under the specified rated current and working system, and under the most unfavorable cooling conditions.


Under normal circumstances, it is not necessary to measure the power factor. When the measurement is required, the total power factor l should be determined.


The measurement of the inherent voltage adjustment rate is calculated based on the data obtained in the light load test and rated current test when the inverter voltage is equal to the rated value (see GB/T 3859.2).


The inspection of auxiliary components is mainly to inspect the performance of auxiliary devices such as inverter electrical components, pumps, and fans. However, as long as these components have a factory certificate, only their operating function in the inverter can be tested, and there is no need to repeat the factory test.


The performance test of the control equipment is best to use a motor of similar rated power to test the equipment, or a lower power motor can be used to conduct the test with the feedback amount properly converted.


The inspection of the protection device mainly includes the overcurrent setting of various overcurrent protection devices; the correct action of the fast fuse and the fast switch. The correct operation of various overvoltage protection facilities; the normal operation of the protection facilities of the cooling system; the correct setting of the grounding device and the switch as a safe operation, and the coordination of various protective devices.


Electromagnetic immunity is to verify the performance of the various sub-components of the inverter through experiments, such as the immunity of power electronic circuits, drive circuits, protection circuits, control circuits, and display and control panels to electromagnetic disturbances. Electromagnetic disturbance has low frequency disturbance and high frequency disturbance. Low-frequency disturbances include harmonics and commutation gaps/voltage distortion; voltage changes, fluctuations, voltage drops and short-term interruptions; voltage imbalances and frequency changes and the impact of power supplies. High-frequency disturbance includes immunity to public environment, industrial environment and electromagnetic field.


The electromagnetic emission should be adapted to its actual working environment conditions as much as possible. In order to ensure the basic protection requirements, low-frequency basic emission limits and high-frequency basic emission limits for public and industrial environments are respectively specified.


The audio noise test is carried out in a place with no sound reflecting surface within 2 m. When testing, try to avoid the interference of turnover environmental noise on the measurement results.


Additional tests are requirements for other properties not included in the above test items, which should be put forward when ordering, and an agreement should be obtained.


5.3 Inverter related tests

                

  1) Steady state performance

                    

   The steady-state performance of the inverter transmission variables, such as output speed, torque, etc., should be tested. Use the selected deviation band (steady state) to illustrate the steady state performance of the feedback control system. Should meet the specified work and use the variable range of the deviation band.


2) Dynamic test

                

  Current limit and current loop These tests are used to characterize the dynamic performance of the inverter, and have nothing to do with the equipment being driven. The following three items can be tested, which should be carried out at close to 0, 50% basic speed, 100% basic speed and field weakening maximum speed (NM).


a) Current limit

                    

   Increasing the load will make the inverter reach its preset current limit point. (Another method is to increase the speed step to a sufficiently large moment of inertia to generate a transient load and make the inverter reach the set current limit point). At this time, the current rise time, overshoot and duration, and damping characteristics can be analyzed.

                    

  B) Current loop bandwidth Through the harmonic analysis of the response between current setting and current measurement (feedback), the bandwidth of the current loop can be determined. The amplitude and displacement must be checked. The test should be carried out in the linear or quasi-linear region.


c) Step response to current setting

  

  Speed ring

                    

  Provide and correctly select the given step of speed to suit the following test. The test can be carried out under no-load or light-load conditions.


a) Reach the current limit and check;


b) In the case of not reaching any limit, measure the transmission output speed response (usually at 50% basic speed, 100% basic speed and maximum field weakening speed NM).


Torque ripple

                    

     If a very sensitive speed measuring device is coupled to the shaft, the relevant level of air gap torque pulsation can be measured by the change of speed under no-load conditions.


Automatic restart

                    

     If there is an automatic restart function, it should be tested during the specified power-off period. This function should be coordinated with the emergency stop and can be stopped if necessary.


3) Energy consumption braking and energy consumption deceleration

Energy consumption braking and energy consumption deceleration are two operating functions, and their characteristics should be negotiated by the user and the manufacturer/supplier. Other performance requirements are determined by the buyer or the manufacturer and the buyer together,


6. Product information

                

  6.1 Logo

                    

  The following items should be marked on the nameplate of the inverter:


a) Name of manufacturer

    b) Inverter model, serial number, year of manufacture

    c) Enter the rated value

    d) Output rating


6.2 Items to be provided

                    

   The following information shall be provided with the equipment:

  

   specifies the information required for calibration components, devices and components adjusted by the user;

     Appropriate selection of the information needed for input and output protection and grounding;

     Instructions for use, including all the information needed to operate the equipment;

     EMC information specified in GB 12668.3;

     Security warning;

    Output phase sequence.

    should provide or make it possible for users to obtain the following information

    Maintenance and operation instructions, including information on finding and replacing faulty components or electronic components; the language should be the language of the country of origin, or the language agreed upon by the manufacturer and the customer;

     The energy absorption rating of the energy consumption braking deceleration and energy consumption braking parking circuit