Skip to product information
1 of 12

PayPal, credit cards. Download editable-PDF and invoice in 1 second!

GB/T 22720.1-2017 English PDF (GBT22720.1-2017)

GB/T 22720.1-2017 English PDF (GBT22720.1-2017)

Regular price $495.00 USD
Regular price Sale price $495.00 USD
Sale Sold out
Shipping calculated at checkout.
Quotation: In 1-minute, 24-hr self-service. Click here GB/T 22720.1-2017 to get it for Purchase Approval, Bank TT...

GB/T 22720.1-2017: Rotating electrical machines -- Qualification and quality control tests of partial discharge free electrical insulation systems (Type ???) used in rotating electrical machines fed from voltage converters

This Part specifies the assessment criteria for stator / rotor winding insulation systems fed from voltage-source pulse-width-modulation (PWM). This Part is applicable to the stator / rotor winding insulation systems of single-phase or multi-phase AC motors powdered by converters. This Part specifies the qualification and quality control (type and exit-factory) tests for typical samples or complete motors, so as to verify the degree of fitness with voltagesource converters.
GB/T 22720.1-2017
GB
NATIONAL STANDARD OF THE
PEOPLE REPUBLIC OF CHINA
ICS 29.160.01
K 20
GB/T 22720.1-2017 / IEC 60034-18-41:2014
Replacing GB/T 22720.1-2008
Rotating Electrical Machines - Qualification and
Quality Control Tests of Partial Discharge Free
Electrical Insulation Systems (Type I) Used in Rotating
Electrical Machines Fed from Voltage Converters
[IEC 60034-18-41:2014, Rotating Electrical Machines - Part 18-41:
Partial Discharge Free Electrical Insulation Systems (Type I) Used in
Rotating Electrical Machines Fed from Voltage Converters -
Qualification and Quality Control Tests, IDT]
ISSUED ON: NOVEMBER 1, 2017
IMPLEMENTED ON: MAY 1, 2018
Issued by: General Administration of Quality Supervision, Inspection and Quarantine;
Standardization Administration of the PEOPLE Republic of
China.
Table of Contents
Foreword ... 3
Introduction ... 6
1 Scope ... 8
2 Normative References ... 8
3 Terms and Definitions ... 9
4 Motor Terminal Voltage Generated during Converter Operation ... 14
5 Electrical Stresses in the Insulation System of Motor Windings ... 18 6 Types of Motor Insulation ... 22
7 Stress Categories for Type I Insulation Systems Used in Motors Fed from Converters ... 22
8 Qualification and Type Tests of Type I Insulation Systems ... 24
9 Test Equipment ... 25
10 Qualification of Type I Insulation Systems ... 27
11 Type Test Procedures of Type I Insulation Systems ... 32
12 Exit-factory Inspection ... 34
13 Analysis, Report and Classification ... 34
Appendix A (informative) Terminal Voltages of a Converter-fed Motor during Operation ... 35
Appendix B (normative) Test Voltages of Type I Insulation Systems ... 38 Appendix C (normative) Derivation of Allowable Voltages in Operation ... 47 Appendix NA (informative) Derivation and Example of Conventional Withstand Voltage Test of Motors with a Rated Voltage of 500 V ... 49
Bibliography ... 50
Rotating Electrical Machines - Qualification and
Quality Control Tests of Partial Discharge Free
Electrical Insulation Systems (Type I) Used in Rotating
Electrical Machines Fed from Voltage Converters
1 Scope
This Part specifies the assessment criteria for stator / rotor winding insulation systems fed from voltage-source pulse-width-modulation (PWM). This Part is applicable to the stator / rotor winding insulation systems of single-phase or multi-phase AC motors powdered by converters.
This Part specifies the qualification and quality control (type and exit-factory) tests for typical samples or complete motors, so as to verify the degree of fitness with voltage- source converters.
This Part is inapplicable to:
---Rotating electrical machines only started by converters;
---Rotating electrical machines whose rated voltage has an effective value of ??? 300 V;
---Rotor windings of rotating electrical machines with an operating voltage (peak value) ??? 200 V.
2 Normative References
The following documents are indispensable to the application of this document. In terms of references with a specified date, only versions with a specified date are applicable to this document. In terms of references without a specified date, the latest version (including all the modifications) is applicable to this document. GB/T 17948.7-2016 Rotating Electrical Machines - Functional Evaluation of Insulation Systems - General Guidelines (IEC 60034-18-1:2010, IDT)
IEC 60034-18-21 Rotating Electrical Machines - Part 18-21: Functional Evaluation of Insulation Systems - Test Procedures for Wire-wound Windings - Thermal Evaluation and Classification
IEC 60034-18-31 Rotating Electrical Machines - Part 18-31: Functional Evaluation of voltage, PDIV is defined as peak to peak voltage.
3.3 Partial Discharge Extinction Voltage
PDEV
Partial discharge extinction voltage refers to the voltage when the voltage applied to the sample gradually decreases from a certain relatively high value where partial discharge is detected to the voltage where no partial discharge can be detected in the test circuit.
NOTE: for sinusoidal voltage, PDEV is defined as the effective value of voltage; for impulse voltage, PDEV is defined as peak to peak voltage.
3.4 Peak (impulse) Voltage
Up
Peak (impulse) voltage refers to the highest voltage value that a unipolar impulse can reach (for example, Up in Figure 1).
NOTE 1: for bipolar impulse voltage, the peak (impulse) voltage is half of the peak to peak voltage (see Figure 2);
NOTE 2: the definition of peak to peak voltage is described in Chapter 4. 3.5 Steady State Voltage Impulse Magnitude
Ua
Steady state voltage impulse magnitude refers to the final magnitude of the impulse voltage (see Figure 1).
3.6 Voltage Overshoot
Ub
Voltage overshoot refers to the magnitude of the peak voltage value exceeding the steady state voltage impulse magnitude (see Figure 1).
3.7 Peak to Peak Impulse Voltage
U???pk/pk
Peak to peak impulse voltage refers to the peak to peak voltage at the impulse repetition rate (see Figure 2).
3.8 Peak to Peak Voltage
3.15 Formette
Formette refers to a special test model used for the evaluation of the electrical insulation systems for form-wound windings.
3.16 Motorette
Motorette refers to a special test model used for the evaluation of the electrical insulation systems for wire-wound windings.
3.17 (electric) Stress
(electric) stress refers to electric field strength, which is expressed in V/mm. 3.18 Rated Voltage
UN
Rated voltage refers to the voltage value of the motor under the conditions of power frequency operation. It is specified by the manufacturer and marked on the nameplate. 3.19 Impulse Voltage Insulation Class
IVIC
Impulse voltage insulation class refers to the safe peak to peak voltage specified by the manufacturer and related to the rated voltage for the motor fed from a specific converter. It is marked in the instruction manual and on the nameplate. 3.20 Fundamental Frequency
Fundamental frequency refers to the frequency in the spectrum obtained through the Fourier transform of the periodic time function. All frequencies in the spectrum are related to it.
NOTE: for this Part, the fundamental frequency of the motor terminal voltage determines the speed of the variable frequency motor.
3.21 Impulse Duration / Width
Impulse duration / width refers to the time interval between the first instant and the last instant when the transient impulse value reaches the specified value of the impulse magnitude or the specified threshold.
3.22 Jump Voltage
Uj
Jump voltage refers to the change of the voltage at the motor terminal at the beginning Key:
???---tr = 50 ns;
???---tr = 100 ns;
???---tr = 200 ns;
???---tr = 1,000 ns;
l---cable length;
Up /Ua---the ratio of peak voltages at the motor and at the converter terminals Figure 4 -- Voltage Increment at Motor Terminal due to Reflection as a Function of Cable Length for Different Impulse Rise Times
5 Electrical Stresses in the Insulation System of Motor
Windings
5.1 Overview
If the winding is subjected to short rise time impulse voltages with an extremely large magnitude, then, high voltage stresses will be generated in the following locations (Figure 5 and Figure 6):
---Between conductors in different phases;
---Between the conductor and the ground;
---Between adjacent turns in the line-end coil.
Due to the space and surface discharge generated in the insulation components, the electrical stress depends on not only the transient voltage itself, but also the peak voltage that the previous insulation withstands. Experience has shown that within a certain effective limit of the various frequency power supply system, the stress parameter is the peak to peak voltage. This is also the reason why the stresses generated by unipolar impulse and bipolar impulse at the same peak to peak voltage value are the same[1].
Key:
a---phase insulation / overhang insulation;
b---ground insulation;
c---turn insulation;
d---slot corona protection;
e---overhang corona protection (stress grading);
1---phase to phase;
2---phase to ground;
3---turn to turn.
Figure 6 -- An Example of Form-wound Winding Design
5.2 Voltage Stress on Phase to Phase Insulation
The maximum voltage stress on the phase to phase insulation is determined by the winding design and the characteristics of the phase to phase voltage.
5.3 Voltage Stress on Phase to Ground Insulation
The maximum voltage stress on the phase to ground insulation is determined by the winding design and the characteristics of the phase to ground voltage.
5.4 Voltage Stress on Turn and Strand Insulation
The electrical stress of the winding insulation is determined by the jump value of the phase to ground voltage and the impulse rise time of this voltage at the motor terminal. For wire-wound windings, the transient voltage distribution depends on the relative position of individual turns in the slot. The impulse of short rise time causes the voltage distribution throughout the coils to be uneven, and high stress is distributed in the first turn or inter-turn (depending on the winding design) of split-phase winding. In fact, the first turn and the last turn may be adjacent to each other, and the inter-turn voltage is almost equal to the voltage that the coil withstands. Take the impulse rise time as a function; the volage applied to the inter-turn insulation in a variety of stators under the most severe circumstance is shown in Figure 7. The shown voltage is a part of the phase to ground jump voltage, and the data can be obtained through the graphs provided in Bibliography [2], [3] and [4]. For specially designed rotating electrical machines, if the manufacturer is aware of the voltage distribution in the coil with a function of the rise time, then, the data can be used to replace Figure 7 to calculate the jump voltage applied to the inter-turn insulation in the most severe circumstance (see Table B.6 of Appendix B). The jump voltage appears at both the rising and falling edges resistant composite insulating materials, the designer can allow the existence of partial discharges.
Another factor that may affect the insulation life is the high-frequency dielectric heating caused by the converter waveform. If the coils have slot corona protection and stress grading, then, the high-frequency current caused by the power supply in these materials may cause overheating and degradation. The repetition frequency and the frequencies related to the rise time of the rising edge will cause the insulating materials to overheat due to dielectric loss. The most severe areas are the main wall insulation, the inter-turn insulation and phase to phase insulation.
6 Types of Motor Insulation
This Part and IEC/TS 60034-18-42 divide winding insulations into two types. Type I winding insulation (Figure 5) is not expected to withstand PD at any part of the insulation during its life. Type II winding insulation (Figure 6) may have to withstand PD in certain parts of the insulation during its life, so PD-resistant materials shall be used. Motors with a rated voltage of 700 V and below may have both Type I and Type II winding insulations. Motors with a rated voltage of above 700 V usually have Type II winding insulation. The manufacturer specifies a rated voltage for each motor at a power frequency, which assumes that the voltage from the power supply is 50 Hz or 60 Hz sinusoidal voltage. When the motor is fed from a converter, although the manufacturer indicates a rated voltage of 50 Hz / 60 Hz and marks it on the nameplate of the motor, the conventional definition of rated voltage is no longer applicable to the winding insulation system. In order to solve this problem, the definition of impulse voltage insulation class is introduced, which is to be separately indicated on the instruction manual and nameplate as described in Appendix C. The classification of Type I insulation can be determined by the absence of partial discharges during operation or when subjected to the test procedures described in this Part. 7 Stress Categories for Type I Insulation Systems Used
in Motors Fed from Converters
In order to obtain sufficient reliability of the electric drive system, the strength of the motor winding insulation system shall be coordinated with the electrical stress that it bears. In other words,
---If the system supplier provides a complete electric drive system, it is responsible for coordinating the strength of the motor winding insulation system and the electrical stress, and ensuring the compatibility of the components, or; ---The drive system integrator shall explain to the motor designer the voltages that appear at the motor terminal, so as to ensure that its design satisfies the motorette or form-wound formette to conduct thermal cycling and treatment procedure tests. The treatment procedure tests include mechanical vibration, moisture exposure and high voltage test. The sample or the complete winding is used for diagnostic test, the purpose of which is the evaluate the existence of PD. The second stage is the type test of the complete winding or motor.
Based on the results of the qualification test and type test, determine the impulse voltage insulation class of the motor, which specifies the maximum allowable voltage applied to the insulation system under the power supply by the converter, expressed in UN (see Appendix C).
8.2 Qualification Test
For this Part, the qualification test is used to study the capability of the insulation systems to withstand various stresses. The qualification test of Type I insulation systems is based on the voltage stress obtained through the thermal cycle and PDIV test before and after other tests specified in IEC 60034-18-21 and IEC 60034-18-31, and one of the stress categories specified in Chapter 7, multiplied by the increase factor described in B.3. In accordance with IEC 60034-18-21 and IEC 60034-18-31, if the thermal class of the insulation systems has been determined, the thermal ageing test only needs to be conducted at any of the three ageing temperatures specified in IEC 60034-18-21 or IEC 60034-18-31.
8.3 Type Test
For Type I insulation systems, partial discharge test needs to be conducted to prove that there is no partial discharge[5][6]. The complete winding or motor is subjected to a voltage suitable for the selected stress category (Table 4), multiplied by the safety factor (Table B.2). For example, for a motor driven by a voltage-source converter, the stress factor of its terminal voltage is 1.3 (benign); the overshoot factor used to calculate the test voltage is 1.5 (overshoot) and 0.3 ??s (see the rise time in B.1). 9 Test Equipment
9.1 PD Measurement at Power Frequency
When a 50 Hz or 60 Hz sinusoidal waveform voltage is applied to the sample, the conventional partial discharge measuring instrument in the laboratory uses a high- voltage coupling capacitor or a radio frequency current transformer. See IEC/TS 60034-27 for the details of the test equipment and methods. The 50 Hz or 60 Hz test voltage and the partial discharge test method described in IEC/TS 60034-27 shall be exclusively used for capacitive samples of single coil, wire-wound motorette and form- wound formette.
9.2 PD Measurement at Impulse Voltage
Generally speaking, the sensitivity of the partial discharge detector decreases with the decrease of the load impedance (or the increase of the capacitance). For reference, the expected sensitivity of the qualification and type tests involved in this Part, at 50 Hz/ 60 Hz, should be 1 pC per nF capacitive load, and the lowest sensitivity is 1 pC. The measurement system that can achieve this sensitivity is considered to be sufficiently sensitive to perform PD test on inductive loads with equal impedance. 9.5 PD Test
9.5.1 Power frequency voltage
When measurements are conducted at 50 Hz / 60 Hz, for the inter-turn samples, wire- wound motorette and form-wound formette samples, this Part specifies that the partial discharge shall be less than 5 pC. These values are also the highest noise level allowed during the measurements. In accordance with the procedures in IEC/TS 60034-27, conduct the partial discharge test.
9.5.2 Impulse voltage
In accordance with IEC/TS 61934, use impulse voltage for PD test; the background noise level is expressed in mV. In accordance with IEC/TS 61934, record the background noise level and the sensitivity.
10 Qualification of Type I Insulation Systems
10.1 Overview
For Type I insulation systems, electrical breakdown test is not used in the qualification of the failure. The samples are subjected to thermal, mechanical cycles and various electrical tests in accordance with IEC 60034-18-21 and IEC 60034-18-31. After each sub-period, perform a partial discharge diagnostic test on the samples. When the partial discharge inception voltage is lower than the test voltage specified by the selected stress category, the end of the test appears.
The qualification test is to compare the performance of a reference system specified in 4.3 of GB/T 17948.7-2016. This reference system has been qualified under the conditions of 10.4. The system to be tested shall withstand the same or a longer ageing cycle as the reference system, and there shall be no partial discharge under the specified test value; the inception voltage is the lowest voltage when the partial discharge can be detected. At the power frequency, in accordance with IEC/TS 60034- 27, within the sensitivity limit stated in 9.4, conduct the measurement. Under the impulse voltage, in accordance with IEC/TS 61934, conduct the partial discharge measurement, which describes the sensitivity checks and reporting requirements. Successful operating experience allows the manufacturer to specify the stress category for the motor with a specially designed insulation system. Under this The partial discharge test performed on the impregnated twisted pair samples cannot be used to evaluate the impregnation resin and manufacturing processes used in the wire-wound motorette, form-wound formette or complete winding. It is allowed to use the wire-wound motorette, form-wound formette or complete winding for this evaluation. 10.3.3 Wire-wound motorette / form-wound formette or complete winding
Use the same materials and processes as the actual coil for sample preparation. When two coils of different phases are located in the same slot, phase to phase insulation will be used, and the model or complete winding shall replicate this design characteristic. When the motor uses impregnated windings, the impregnated sample shall be tested. The phase to phase insulation and the main wall insulation shall replicate all creepage distances and electrical clearances (phase to phase) in the finished windings. For each type of insulation being tested, the sample shall replicate the insulating materials and the thickness used in the product. Under the circumstance of testing the complete winding, in accordance with the procedures provided in 11.2 and 11.3, conduct the test.
10.4 Qualification Test
10.4.1 Overview
The purpose of the qualification test is to conduct a thermal ageing test on the insulation system components and related parts in accordance with IEC 60034-18-21 or IEC 60034-18-31, so as to determine at what point partial discharge inception occurs below the specified test voltage. In the test conclusion, the stress categor...

View full details