GB/T 21707-2025 PDF English
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| GB/T 21707-2025 | English | 515 |
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Insulation specification for frequency conversion machine
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| GB/T 21707-2018 | English | 150 |
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Insulation specification for variable frequency adjustable speed definite purpose converter-fed three-phase induction motors
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| GB/T 21707-2008 | English | 359 |
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Insulation specification for variable frequency adjustable speed definite purpose converter-fed three-phase induction motors
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GB/T 21707-2025: Insulation specification for frequency conversion machine---This is an excerpt. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.), auto-downloaded/delivered in 9 seconds, can be purchased online: https://www.ChineseStandard.net/PDF.aspx/GBT21707-2025
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 29.160.01
CCS K 20
Replacing GB/T 21707-2018
Insulation specification for frequency conversion machine
Issued on: MAY 30, 2025
Implemented on: DECEMBER 01, 2025
Issued by. State Administration for Market Regulation;
Standardization Administration of the People’s Republic of China.
Table of Contents
Foreword... 3
1 Scope... 5
2 Normative references... 5
3 Terms and definitions... 6
4 Technical requirements... 10
5 Test methods and test equipment... 14
6 Inspection rules... 17
Appendix A (Normative) Measurement guidelines for waveform parameters of high-
frequency impact testers... 18
Appendix B (Informative) High-frequency impact test system and influencing factors
... 20
Appendix C (Informative) Testing of the volatile matter of impregnating resin... 22
Appendix D (Informative) Procedure for evaluating the thermal resistance of insulation
structures under special working conditions - Example of evaluating the thermal
resistance of insulation structures of drive motors for new energy vehicles... 24
Appendix E (Informative) Evaluation regulations for the insulation structure of variable
frequency motors... 30
Bibliography... 34
Insulation specification for frequency conversion machine
1 Scope
This document specifies the technical requirements, test methods, test equipment and
inspection rules for insulation of frequency conversion machine.
This document is applicable to frequency conversion machine with rated voltage of 1
140 V and below. It serves as a reference for the implementation of high-voltage
variable-frequency motors with a rated voltage higher than 1 140 V.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this
document and are indispensable for its application. For dated references, only the
edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
GB/T 4074.7-2024, Test methods of winding wires - Part 7.Test procedure for
the determination of the temperature index of enamelled winding wires
GB/T 5591.3-2018 Combined flexible materials for electrical insulation - Part 3.
Specifications for individual materials
GB/T 6109.1, Enamelled round winding wire - Part 1.General requirements
GB/T 7095.1, Enamelled rectangular copper winding wires - Part 1.General
requirements
GB/T 11026.4-2012, Electrical insulating materials - Thermal endurance
properties - Part 4.Ageing ovens - Single-chamber ovens
GB/T 17948.1-2018, Rotating electrical machines - Functional evaluation of
insulation systems - Test procedures for wire-wound windings - Thermal
evaluation and classification
GB/T 17948.3-2017, Rotating electrical machines - Functional evaluation of
insulation systems - Test procedures for form-wound windings - Thermal
evaluation and classification of insulation systems used in rotating machines
GB/T 20629.3-2019, Non-cellulosic papers for electrical purposes - Part 3.
Unfilled aramid (aromatic polyamide) papers
GB/T 22720.1-2017, Rotating electrical machines - Qualification and quality
control tests of partial discharge free electrical insulation systems (Type j) used
in rotating electrical machines fed from voltage converters
GB/T 22720.2-2019, Rotating electrical machines - Qualification tests for the
partial discharge resistant electrical insulation systems (Type Ⅱ) used in rotating
electrical machines fed from voltage converters
JB/T 10508-2020, Specifications for slot wedges used in small and middle size
electric machines
3 Terms and definitions
For the purposes of this document, the following terms and definitions, as well as those
given in GB/T 22720.1-2017, apply.
3.1
type Ⅰ insulation systems
The insulation structure, for converter-powered motors, which is not subject to partial
discharge during its service life.
3.2
type Ⅱ insulation systems
The insulation structure, for converter-powered motors, which is subject to partial
discharge in any part during its service life.
Note. Generally, motors with a rated voltage greater than or equal to 700 V are of
type Ⅱ insulation systems.
3.3
impulse voltage insulation class; IVIC
The safe peak-to-peak voltage, for inverter-powered motors, specified by the
manufacturer and related to the rated voltage, which shall be indicated in the
instructions and on the nameplate.
[Source. GB/T 22720.1-2017, 3.19, modified]
3.4
partial discharge; PD
3.12
rated voltage
UN
The voltage value of the motor under power frequency operating conditions, which is
specified by the manufacturer and marked on the nameplate.
Note 1.The rated voltage is the line end rated voltage and is the effective value.
Note 2.For electric vehicle drive motors, the rated voltage is the nominal voltage of
the DC bus declared by the manufacturer, in which case UN = Udc.
[Source. GB/T 22720.1-2017, 3.18]
3.13
overshoot factor; OF
The ratio of the motor terminal display voltage to the converter voltage.
[Source. GB/T 22720.1-2017, 3.24]
4 Technical requirements
4.1 Requirements for single materials
4.1.1 Electromagnetic wire
4.1.1.1 General requirements
In addition to meeting the requirements of Table 1, the electromagnetic wire shall also
withstand the tension during the winding process, and the paint film/insulation layer
shall have a certain degree of flexibility during the winding process, without cracking
or losing adhesion.
4.1.1.2 High-frequency impact resistance
The chemical structure and coating process of the electromagnetic wire paint film shall
enable the electromagnetic wire to effectively withstand the long-term impact of high-
frequency impulse voltage. Under the conditions described in 4.3.1.2, the high-
When using mica tape for insulation, its general performance shall meet the technical
requirements of the relevant mica tape product standards.
4.1.4 Slot wedge
The heat resistance grade of the slot wedge shall not be lower than 155(F), and its
conventional performance shall meet the technical requirements of JB/T 10508-2020.
4.1.5 Lead wire
The conductor inside the lead wire shall be guaranteed to operate continuously at a
temperature not lower than 125 ℃. The connection between the lead wire and the
winding wire can be protected by corresponding thermal-setting adhesive tape, and its
general performance shall meet the relevant product technical requirements.
4.1.6 Casing
The heat resistance grade of the casing shall not be lower than 155(F), and its
conventional performance shall meet the relevant product technical requirements.
4.2 Technical requirements for insulation structure
4.2.1 Heat resistance grade
The heat resistance grade corresponding to the continuous use design life of the
insulation structure shall not be lower than 155(F).
4.2.2 Technical requirements for type Ⅰ insulation systems
Type Ⅰ insulation systems shall meet the technical requirements of GB/T 22720.1-2017.
4.2.3 Technical requirements for type Ⅱ insulation systems
Type Ⅱ insulation systems shall meet the technical requirements of GB/T 22720.2-2019.
4.2.4 High-frequency impact resistance requirements
The design and manufacturing process of type Ⅱ insulation systems shall enable the
insulation structure to effectively withstand long-term impact of high-frequency
impulse voltage. For the high-frequency impact resistance of the insulation structure
evaluated under the conditions described in 4.3.6.2, the insulation structure shall meet
the requirements of Table 4.
Bipolar high-frequency impulse voltage is preferred for testing. If the test voltage is too
high to meet the requirements, such as exceeding 20 kV, the test method in Appendix C
of GB/T 22720.2-2019 may be used after consultation between the supply and demand
parties, and its requirements shall be met.
5 Test methods and test equipment
5.1 Evaluation of high-frequency impact resistance of electromagnetic wire
5.1.1 Test sample
For the evaluation of the high frequency impact resistance of electromagnetic wire,
prepare the test samples as follows.
a) Enameled round copper wire. Prepare into "twisted pair" form according to the
provisions of 5.1.1 of GB/T 4074.7-2024.
b) Enameled rectangular copper wire. Prepare into "back-to-back" form
according to the provisions of 5.1.2 of GB/T 4074.7-2024.Straightening can
be done by stretching the sample by no more than 1% of its total length, and
tying the two lines tightly together with a high-temperature binding wire that
can withstand long-term use of 155°C and above. The length of the "back-to-
back" straight part is 150 mm.
5.1.2 Test conditions
In an aging oven at a temperature of 155 °C (the aging oven shall meet the relevant
provisions of GB/T 11026.4-2012), the electromagnetic wire samples are continuously
tested using a high-frequency impact tester with the parameters shown in Table 5.The
measurement guidelines for waveform parameters of high-frequency impact testers are
given in Appendix A.
5.1.3 Test results
When evaluating the high-frequency impact resistance of 5 samples, take the median
and minimum values as the sample results.
5.2 Determination of volatile matter of impregnating resin
The method for determining the volatile matter of the impregnating resin is shown in
Appendix C.
5.3 Heat resistance assessment of insulation structures
The heat resistance assessment of insulation structures shall be carried out in
accordance with the provisions of GB/T 17948.1-2018 or GB/T 17948.3-2017.
For the heat resistance assessment of insulation structures under special working
conditions, Appendix D provides an example of the heat resistance assessment of the
insulation structure of the drive motor of a new energy vehicle.
5.4 Evaluation of type Ⅰ insulation systems
Appendix E briefly describes the evaluation procedures for type Ⅰ insulation systems
and type Ⅱ insulation systems of variable frequency motors.
Evaluate the type Ⅰ insulation systems according to the procedures of GB/T 22720.1-
2017, as described in E.2.Based on the identification test results, obtain the impulse
voltage insulation class of the insulation system according to the method described in
E.2.3.
5.5 Evaluation of type Ⅱ insulation systems
Evaluate the type Ⅱ insulation systems according to the procedures of GB/T 22720.2-
2019, as described in E.3.
5.6 Evaluation of high-frequency impact resistance of insulation structures
5.6.1 Test products and test samples
The test may be carried out using a randomly wound dummy coil (motorette), a formed
wound dummy coil (formette), an actual motor stator winding or a portion of an actual
winding. The test product is a complete fixture containing a test sample, and the test
sample is the coil in the test product. Each test product may contain several individual
test samples.
5.6.3 Test results
For the model coil, 5 test samples shall be used to evaluate the high-frequency impact
resistance performance. For the actual winding, 3 test samples shall be used to evaluate
the high-frequency impact resistance performance. The median and minimum values
shall be taken as the test results.
6 Inspection rules
6.1 Inspection of single insulating materials and electromagnetic wires
The high-frequency impact resistance of electromagnetic wires shall be tested during
the first batch of purchase confirmation and annual random inspection.
For other insulating materials, follow the normal incoming inspection method.
6.2 Inspection of the overall insulation structure
Inspection of the overall insulation structure of the motor shall be carried out during
motor product identification and when the insulation structure is changed.
......
Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al.
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