I. The main inspection tests of china permanent magnet synchronous motor are:

Determination of the insulation resistance between the windings and the casing as well as between the windings themselves; Measurement of the DC resistance of the winding in the actual cold state; No-load test; Dielectric strength test of insulation between windings and the casing and between windings. When necessary, conduct inter-turn insulation dielectric strength tests of the windings.

Ii. Inspection and Test Methods for china permanent magnet synchronous motor:

a) Visual inspection: Check if the shape is complete, if the marking at the outlet end is correct, if the screws, bolts and nuts used for fastening are tightened, if the rotor rotates flexibly, the radial deflection of the motor shaft extension and the vibration condition, etc. For wound-rotor motors, the assembly quality of brushes, brush holders and collector rings should also be inspected, as well as whether the contact between brushes and collector rings is good. For closed self-fan-cooled motors, the exhaust system should be inspected.

b) Measurement of insulation resistance: For repaired motors, generally only the cold-state (normal temperature) insulation resistance between phases and between phases and ground of the windings is measured. For wound-rotor motors, the insulation resistance of the rotor windings should also be measured. For multi-speed winding motors, the insulation resistance of each winding should be measured separately and one by one. For large electric motors, it can be determined whether the windings are damp by measuring the insulation resistance. For motors with a rated voltage of less than 500V, a 500V megohmmeter is generally used for measurement, while for motors with a rated voltage between 500 and 3000V, a 1000V megohmmeter is used. A 2500V megohmmeter should be used for motors with a voltage of over 3000V. For motors with a voltage of 500V or less, the insulation resistance should not be lower than 0.5MΩ. All replaced windings should not be less than 5MΩ.

c) Measurement of DC resistance: The measurement of the DC resistance of the motor winding is generally carried out in a cold state. The ratio of the error between the measured resistance values of each phase to the average value of the three phases shall not exceed 5%. If the resistance values differ too much, it indicates that there is a short circuit, open circuit, poor welding or contact in the winding, or the number of turns in the winding is incorrect, etc. If the resistance of all three phases exceeds the specified range, it indicates that the winding wire is too thin.

d) Withstand voltage test: When the stator windings of an electric motor are insulated with insulating materials between phases and between phases and ground, and can withstand a certain voltage without breakdown, it is called withstand voltage. Both AC withstand voltage and DC withstand voltage are withstand voltage tests and are methods for assessing the insulation strength of power equipment.

Dc withstand voltage test: It has a relatively high voltage and plays a special role in detecting certain local defects in insulation. It can be conducted simultaneously with the leakage current test. Compared with AC withstand voltage tests, DC withstand voltage tests have the advantages of lightweight test equipment, less damage to insulation and easier detection of local defects in equipment. Compared with AC withstand voltage tests, the main drawback of DC withstand voltage tests is that due to the different voltage distribution inside the insulation under AC and DC conditions, the test of insulation by DC withstand voltage tests is not as close to reality as that by AC.

Ac withstand voltage test: The AC withstand voltage test is a very strict test for insulation and can effectively detect more dangerous concentrated defects. It is the most direct method for assessing the insulation strength of electrical equipment, which is of decisive significance for determining whether the electrical equipment can be put into operation. It is also an important means to ensure the insulation level of the equipment and avoid insulation accidents. Sometimes, AC withstand voltage tests may further develop some weak points in insulation. Therefore, before the test, the test samples must be tested for insulation resistance, absorption ratio, leakage current and dielectric loss, etc. Only when the test results are qualified can the AC withstand voltage test be carried out.

1) Stator winding: During handover tests, take 1 kilovolt for rated voltages of 0.4 kilovolts and below, and 10 kilovolts for rated voltages of 6 kilovolts. For motors in operation and those with stator windings not replaced or partially replaced during major overhauls, take 1.5 times the rated voltage, but it must not be lower than 1000 volts. For motors with all stator windings replaced, take twice the rated voltage plus 1000 volts, but it must not be lower than 1500 volts. For low-voltage motors with a capacity of less than 100 kilowatts that are not very important, the AC withstand voltage test can be conducted using a 2,500-volt megohmmeter.

2) Rotor winding: During the handover test, take 1.5 times the rated voltage for irreversible rotors and 3 times the rated voltage for reversible rotors.

Note: For the AC withstand voltage test of the rotor coil of a synchronous motor, the test voltage should be 7.5 times the excitation voltage, but it should not be lower than 1200V and should not exceed 75% of the factory test voltage.

e) Inter-turn insulation test: Increase the power supply voltage to 130% of the rated voltage and let the motor idle for 5 minutes. If no short circuit occurs, it is called an inter-turn insulation test. Its purpose is to assess the insulation performance between turns.

f) Determination of rotor open-circuit voltage: When measuring the rotor open-circuit voltage, the rotor remains stationary, the rotor winding is open-circuited, the starting rheostat is disconnected, and the rated voltage is applied to the stator winding. The voltage between each line is measured between the rotor and the stator rings. For motors with a rated voltage above 500V, the voltage applied to the stator winding can be appropriately reduced.

g) No-load test: A no-load test involves applying a three-phase balanced voltage to the stator windings of an electric motor to operate it without load. The purpose of this test is to determine the no-load current and no-load loss, and to separate iron loss and mechanical loss (including wind and friction loss) from the no-load loss.

During no-load tests, it is necessary to observe the operation of the motor, listen for any abnormal sounds, whether the core is overheating, the temperature rise of the bearings and whether the operation is normal. For wound-rotor motors, it is necessary to check whether there are sparks and overheating phenomena in the brushes.

For repaired asynchronous motors, when conducting no-load tests, it is usually only necessary to measure the no-load current to check the quality of the motor after repair. No-load loss tests should only be conducted when necessary.

Iii. General Inspection Before DC Motor Test

a) Conduct a general inspection of the assembly quality of the motor (such as whether the fasteners are tightened and whether the rotor rotates flexibly); The brush grips should be firmly and precisely fixed on the brush frame. The lower edge of the brush grips should be parallel to the surface of the commutator, and the distances between each brush grip should be equal. The brush should be able to move freely up and down within the brush holder, but it should not be too loose. The surface of the brush should fit well with the commutator. The spring pressure at the top of the brush should be adjusted appropriately. The surface of the commutator should be clean and smooth. The mica sheets between the commutator segments must not protrude above the commutator surface, and the recessed depth should be 1-1.5mm. Check whether the outgoing wires of the motor are correct.

b) Use a plug gauge to check the air gap under each magnetic pole on the circumference of the armature, and measure at both ends of the motor's axial direction each time. The maximum allowable deviation value of the air gap should not exceed ±10% of its arithmetic mean.

The following tests are usually conducted on the repaired DC motor:

a) Check the polarity of the motor windings and the correctness of their connections; Check the correctness of the connection between the main magnetic pole and the commutator winding; Check the correctness of the connection between the series-excited and shunt windings (or between each shunt winding). When determining and measuring the insulation resistance between the windings and the casing as well as among the windings themselves, in addition to measuring the insulation resistance between each winding and the casing and among them, the insulation resistance between the wire clamps of the armature winding and the commutator, between the commutator tight coil and the commutator segments, and between the brush holder and the casing (at this time, the brush should be lifted) should also be measured. The insulation resistance value should not be lower than the value calculated by the following formula, that is, R=UN/ (1000+PN/100), where R is the insulation resistance (MΩ). UN - Rated voltage of the motor (V); PN - Rated Power of the motor (KW);

b) Measure the DC resistance of the winding using a double-arm bridge. The measurement should be conducted three times, with the arithmetic mean taken. At the same time, the ambient temperature should be measured with a thermometer. When all the windings of the motor are correctly connected, to ensure the good operating performance of the motor, the brushes of the motor must be placed at the geometric neutral line position. If there is a need to replace the windings, inspect the commutator, or have doubts about the insulation of the windings, conduct a withstand voltage test between each winding and the commutator and the casing, as well as between each winding.

c) If all the above tests are qualified, the motor can be powered on for no-load testing.

d) Generally, DC motors that have undergone maintenance do not need to undergo load tests.

china permanent magnet synchronous motor https://www.juyueenergy.com/Permanent-magnet-synchronous-motor