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This standard is developed in accordance with the rules given in GB/T 1.1-2009.
This standard replaces GB/T 12665-2008 Requirements of Requirements of Damp-heat Testing of Electrical Machine for Service in General Environmental Condition, and the following technical changes have been made with respect to GB/T 12665-2008 (the previous edition):
——Normative References, i.e. Chapter 2, is updated;
——"withstand voltage" is changed to "electrical strength" (see 3.3);
——cyclic damp-heat testing method is modified and Method 2 is added (see 4.2);
——Figure 2 is added;
——damp-proof humidifier is deleted and Note 1 is added (see 4.3 of 2008 edition);
——testing methods for leakage current after damp-heat test are added (see 4.4).
This standard was proposed by China Electrical Equipment Industry Association.
This standard is under the jurisdiction of the National Technical Committee 26 on Electric Rotating Machinery of Standardization Administration of China (SAC/TC 26).
The previous editions replaced by the standard are as follows:
——GB/T 12665-1990, GB/T 12665-2008.
Requirements of Damp-heat Testing of Electrical Machine for Service in General Environmental Condition
1 Scope
This standard specifies the methods, technical requirements and inspection rules for damp-heat testing of rotating electrical machine for service in general environmental condition.
This standard is applicable to various rotating electrical machines (excluding micro-control electrical machine, hereafter referred to as electrical machine).
2 Normative References
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 755 Rotating Electrical Machines – Rating and Performance
GB/T 2423.3-2006 Environmental Testing for Electric and Electronic Products - Part 2: Testing Method Test Cab: Damp Heat Steady State
GB/T 2423.4-2008 Environmental Testing for Electric and Electronic Products - Part 2: Test Method - Test Db: Damp Heat, Cyclic (12h+12h Cycle)
GB/T 12113-2003 Methods of Measurement of Touch Current and Protective Conductor Current
3 Technical Requirements
3.1 Insulation resistance
3.1.1 The insulation resistance value between complete electrical machine winding against enclosure and that between windings shall not be less than the following values:
a) For the electrical machine with rated voltage of 220V or above, it shall be determined according to Formula (1):
(1)
Where,
R——the insulation resistance of electrical machine winding, MΩ;
U——the rated voltage of electrical machine winding, V;
P——the electrical machine capacity, kW.
b) For the electrical machine with rated voltage greater than 36V but less than 220V, it's 0.22MΩ;
c) For the electrical machine with rated voltage less than 220V, it's 0.1MΩ;
d) Where multiple windings exist in the electrical machine, it shall be measured and calculated respectively.
3.1.2 Where parts and components of large electrical machine are subject to damp-heat testing, the insulation resistance converted to complete machine shall be determined according to Formula (2).
(2)
Where,
R′——the insulation resistance value converted to complete machine, MΩ;
n——the number of main shunt circuit of stator or rotor circuit (the number of shunt circuits shall be determined according to Table 1);
Rn——the insulation resistance value of each shunt circuit, which is calculated as the tested average insulation resistance of the specimen in case of parallel connection, divided by the number of branch circuits of such shunt circuit (the number of branch circuits shall be determined according to Table 2);
——the reciprocal sum of main parallel shunt circuit insulation resistances of stator or rotor circuit.
Table 1 Number of Main Shunt Circuits of Stator or Rotor Circuit
Name Main components Number of shunt circuits
DC electrical machine stator circuit Main pole assembly, electronic control and similar components 1
Current electrical machine armature circuit Commutator, armature winding, brush carrier assembly, commutating pole assembly, compensating winding, exciting winding, electronic control and similar components to them Calculated according to the actually existing main components in armature circuit
AC electrical machine stator circuit Stator winding 1
Winding-type asynchronous electrical machine rotor circuit Brush carrier assembly, collector ring and rotor winding 3
Synchronous electrical machine rotor circuit Brush carrier assembly, collector ring and magnetic pole assembly (or magnetic pole winding) 3
Table 2 Number of Branch Circuits of the Shunt Circuit of Stator or Rotor Circuit
Name Number of branch circuits
Commutator and collector ring 1
Main pole assembly, commutating pole assembly, compensating winding and exciting winding The same as number of poles
Winding-type asynchronous electrical machines rotor winding, DC electrical machine armature winding and AC electrical machine stator winding The same as number of slots
Brush carrier assembly The same as number of brush carriers
3.2 Leakage current
Leakage current of electrical machine shall not be greater than the limit value specified in relevant product standards.
For parts and components of large electrical machine, leakage current values are not assessed.
3.3 Electrical strength
The insulation of electrical machine winding against enclosure and that between windings shall be able to withstand 85% of the test voltage specified in GB/T 755 for 1min without breakdown.
The insulation of parts and components of large electrical machine shall be able to withstand 85% of the test voltage specified in GB/T 755 for 1min without breakdown.
3.4 Operation performance
Electrical machine shall be able to operate normally and be free from clamping stagnation or other phenomenon affecting its normal operation, and its performance shall reach the requirements of relevant product standards.
Note: for the electrical machine equipped with damp-proof heater, damp-heat testing assessment may not be conducted.
3.5 Others
Where relevant professional products are subject to steady-state damp-heat testing according to 4.2, corresponding test cycle and technical requirements after damp-heat testing shall be specified but shall not be lower than those specified in this standard.
Large turbo-generator and hydro-generator may not be subject to damp-heat testing and whether heater will be installed shall be determined through negotiation between the user and the manufacturer.
4 Test Methods
4.1 Preparation before test
4.1.1 Test equipment and apparatus
Damp-heat testing chamber shall meet the requirements of Chapter 4 in GB/T 2423.4-2008.
The voltage grade of tramegger for measurement of insulation resistance shall meet those specified in Table 3.
Table 3 Voltage Grade of Tramegger for Measurement of Insulation Resistance
Rated voltage of electrical machine
V Working voltage of tramegger
V
≤36
>36~500
>500~1 000
>1 000 250
500
1 000
25 000
4.1.2 Specimen requirements
Where the parts and components of large electrical machine is subject to testing, aluminum foil electrode shall be adopted for measurement of high-voltage stator winding and DC electrical machine compensating winding; the coil for slotted insulation and that dipped in paint shall be made into simulated slot; the length of aluminum foil electrode and simulated slot shall be the same as the actual core length generally. Where limited by product dimension, the smaller simulator with the same material, insulation structure and process may also be adopted for testing.
4.1.3 Specimen pretreatment
Before damp-heat testing, the specimen shall be placed in damp-heat testing chamber for preheating treatment at the temperature of 25~35℃ for a period not be less than 8h, as counted when the temperature of damp-heat testing chamber reaches 25℃.
4.2 Methods for damp-heat testing
Cyclic damp-heat testing shall be conducted according to GB/T 2423.4-2008; 40℃ is generally selected as the high temperature and 55℃ may also be selected according to severe degree of service occasion; there are two methods (See Figures 1 and 2) for temperature reduction, and either of them may be selected for testing; see Figures 1 and 2 for the testing cycle, and 6 cycles shall be conducted. Complete electrical machine or its parts and components (only for large electrical machine) shall meet the requirements of 3.2~3.5 after being subject to damp-heat testing specified in this clause.
Method 1 (see figure 1):
Temperature shall drop to 25±3℃ within 3h~6h. The cooling rate in the first 1.5h shall be in accordance with Figure 1 and the temperature within 3h±15min reaches 25±3℃. The relative humidity in the first 15min shall not be less than 90% and that in the remaining time shall not be less than 95%.
Method 2 (see figure 2):
Temperature shall drop to 25±3℃ within 3h~6h, but there are no additional requirements for the first 1.5h as specified in Method 1, and the relative humidity shall not be less than 80%.
Note: refer to GB/T 2423.4-2008 for the selection of Method 1 or 2.
According to the electrical machine service occasion conditions, product may also be subject to steady-state damp-heat testing at the temperature of 40±2℃, and humidity of 90%~95% for 48h according to GB/T 2423.3-2006.
