GB/T 38090-2019Technical requirements of permanent magnets for drive motor of electric vehicle (English PDF)

5.3 Resistivity

The resistivity of permanent magnets perpendicular to the direction of easy magnetization shall be not less than 1.22 µohm - m; the resistivity of permanent magnets parallel to the direction of easy magnetization shall be not less than 1.38 µohm - m.

5.4 Bending Strength

The bending strength of permanent magnets perpendicular to the direction of easy magnetization shall be not less than 220 MP; the bending strength of permanent magnets parallel to the direction of easy magnetization shall be not less than 180 MPa.

5.5 Product Magnetic Moment Consistency

Product magnetic moment consistency (at the temperature condition of 20 °C) shall satisfy the following requirements: the magnetic moment deviation of permanent magnets whose mass is above 10 g shall be less than 4%; the magnetic moment deviation of permanent magnets whose mass is between 5 g ~ 10 g shall be less than 6%; the magnetic moment deviation of permanent magnets whose mass is below 5 g shall be less than 8%.

5.6 High Temperature Irreversible Magnetic Loss

The high temperature irreversible magnetic loss of permanent magnets shall be determined by the demand-side and the supply-side through negotiation.

5.7 Plating (or coating) Thickness

After surface treatment, the thickness range of the central plating (or coating) of permanent magnets is 3 µm ~ 70 µm; plating (or coating) thickness at the corners is allowed to be different from the thickness of the magnetic body's central location, but this thickness difference shall be not more than 30 µm.

5.8 Corrosion Resistance

Corrosion resistance of permanent magnets shall satisfy the requirement of salt spray test time stipulated in Table 3. After the test, permanent magnets shall reach the requirements of protection rating and appearance rating Level-10 as stipulated in GB/T 6461-2002.

6.1 Magnetic Property

The test of main magnetic properties of permanent magnets shall comply with the stipulations in GB/T 3217 or GB/T 29628.

6.2 Temperature Coefficient

The test of temperature coefficient of permanent magnets shall comply with the stipulations in GB/T 24270.

6.3 Resistivity

The measurement method of electrical resistivity of permanent magnets shall comply with the stipulations in Appendix B.

6.4 Bending Strength

The test of bending strength of permanent magnets shall comply with the stipulations in GB/T 31967.2.

6.5 Product Magnetic Moment Consistency

The measurement of magnetic moment of permanent magnets shall comply with the stipulations in IEC 60404-14. Product magnetic moment consistency is the ratio of sampling product's magnetic moment range (the difference between the maximum value and the minimum value) and the average value.

6.6 High Temperature Irreversible Magnetic Loss

The measurement of high temperature irreversible magnetic loss of permanent magnets shall refer to the method described in Appendix C.

6.7 Plating (or coating) Thickness

The measurement of plating (or coating) thickness of permanent magnets shall comply with the stipulations in GB/T 6462.

If there are multiple metal plating, then, measure the total thickness of the plating.

6.8 Corrosion Resistance

The test of corrosion resistance of permanent magnets shall comply with the stipulations in GB/T 10125.

7.4 Inspection Result Determination and Re-inspection Rules

When each inspection item is qualified in product inspection, then, this batch of products shall be determined as qualified. If there are disqualified items, take double size of samples from this batch of products to conduct re-inspection of the disqualified items. In re-inspection, when all the re-inspection items are qualified, then, this batch of products shall be determined as qualified. If there are still disqualified items in re-inspection, then, this batch of products shall be determined as disqualified.

The result determination and re-inspection rules of type inspection shall be determined by the demand-side and the supply-side through negotiation.

8.1 Marking

8.1.1 Each batch of products shall be attached with product certificate and quality warranty; seals of inspector and quality inspection department.

8.1.2 Product certificate shall indicate:

a) Product name (or representative symbol), dimensions and batch number;

b) Quantity;

c) Date of inspection;

d) Manufacturer's name and address;

e) Inspector's code and inspection department's seal;

f) Serial number of Standard being implemented.

8.1.3 If applicable, quality warranty shall include:

a) Product name (or representative symbol);

b) Serial number of Standard being implemented;

c) Specifications and dimensions;

d) Quantity;

B.4 Measurement Procedures

Measurement procedures are:

a) As it is shown in Figure B.1, connect Contact End 1 and Contact End 2 with current supply; connect Contact End 3 and Contact End 4 with nanovoltmeter.

In accordance with the thickness of specimen, set the output current of current supply to be I12; meanwhile, read the reading on the nanovoltmeter U43;

b) Similarly, connect Contact End 2 and Contact End 3 with current supply; connect Contact End 1 and Contact End 4 with nanovoltmeter; re-set the output current of current supply to be I23; I23 shall be equal to I12. Meanwhile, read the reading on the nanovoltmeter U14;

c) In accordance with Formula (B.1), calculate electrical resistivity:

Where, rho---electrical resistivity, expressed in (µohm - m); d---specimen thickness, expressed in (mm);

U43---voltage between Contact End 4 and Contact End 3, expressed in (mV);

U14---voltage between Contact End 1 and Contact End 4, expressed in (mV);

I12---current between Contact End 1 and Contact End 2, expressed in (A);

I23---current between Contact End 2 and Contact End 3, expressed in (A).

C.3 Measurement Method 2

C.3.1 The ambient temperature of measurement is 20 °C. Before measurement, in order to make specimen temperature consistent with the ambient temperature, specimens shall be placed in room temperature environment for not less than 30 min.

C.3.2 Magnetize specimens, till they become saturated.

C.3.3 Adopt flux meter, match with Helmholtz coil, in accordance with IEC 60404-14, measure magnetic flux Phi0.

C.3.4 Place specimens on an iron plate, which has the thickness of 3 mm ± 0.1 mm and the texture of Q235. The N-pole and S-pole of each magnetic steel shall be interlaced; the interval is the longest side distance of magnetic steel. In addition, the direction of the magnetic pole shall be vertical to the iron plate plane. Place the specimens, along with the iron plate, into high-temperature chamber. Wait till the high-temperature chamber reaches the set measurement temperature 180 °C, conduct thermal insulation for 2 h. Temperature fluctuation of the high-temperature chamber shall be controlled within ± 2 °C.

C.3.5 After the thermal insulation is completed, take the specimens, along with the iron plate, out of the high-temperature chamber. Then, naturally cool them down to room temperature.

C.3.6 Measure magnetic flux Phit after the test. In accordance with Formula (C.1), calculate the magnetic attenuation.

C.3.7 Repeat C.3.4 ~ C.3.6 for 4 times in total.

C.3.8 In accordance with the above-mentioned methods, it is measured that after 5 high-temperature cycles, the average irreversible magnetic loss (magnetic attenuation) […]