GB/T 22720.1-2017Rotating 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 (English PDF)

Foreword

Electrical Insulation Systems Used in Rotating Electrical Machines Fed from Voltage

Converters is divided into two parts.

---GB/T 22720.1 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;

---GB/Z 22720.2 Rotating Electrical Machines - Qualification and Acceptance

Tests for Partial Discharge Resistant Electrical Insulation Systems (Type II)

Used in Rotating Electrical Machines Fed from Voltage Converters.

This is Part 1 of Electrical Insulation Systems Used in Rotating Electrical Machines

Fed from Voltage Converters.

This Part was drafted in accordance with the rules in GB/T 1.1-2009.

This Part serves as a replacement of GB/T 22720.1-2008 Rotating Electrical Machines

- Qualification and Type Tests for Type I Electrical Insulation Systems Used in Rotating

Electrical Machines Fed from Voltage Converters. In comparison with GB/T 22720.1-

2008, the main technical changes are as follows.

---The Scope is modified (see Chapter 1; Chapter 1 of Version 2008);

---The term "Impulse Voltage Insulation Class" is added (see 3.19);

---The temperature selection for qualification test is modified (see 8.2; 8.2 of

Version 2008);

---The "pre-diagnostic test" is added (see 10.4.2);

---The procedures for the type test of Type I insulation systems are modified (see

Chapter 11; Chapter 11 of Version 2008);

---The "exit-factory test" is added (see Chapter 12);

---The "requirements for the application of impulse voltage" are added (see B.2);

---The "partial discharge test enhancement factors" are added (see B.3);

---Appendix C is added (see Appendix C);

---Appendix NA is added (see Appendix NA).

This Part uses the translation method in the identical adoption of IEC 60034-18-

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.

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)

3 Terms and Definitions

The following terms and definitions are applicable to this document.

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.

4 Motor Terminal Voltage Generated during Converter Operation

Due to the switching characteristics of power semiconductor devices, the rise time of

the current converter output voltage can be within the range of 0.05 µs ~ 2 µs. IEC/TS

61800-8 may be used to calculate the motor terminal voltage fed from the converter,

and the motor terminal voltage depends on several characteristics of the power supply

system, such as.

5 Electrical Stresses in the Insulation System of Motor Windings

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.

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.

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,

8 Qualification and Type Tests of Type I Insulation Systems

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).

9 Test Equipment

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.

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