How does the multimeter detect the quality of the motor

1. How to quickly judge whether the motor is good or bad:

1. Use a multimeter to measure the DC resistance of the three-phase windings of the motor. The closer the results of the three measurements are, the better. The winding resistance is qualified within 2%, and when the phase difference is more than 10%, the phase with the smaller resistance may have an inter-turn short circuit.

2. Measure the insulation resistance between phases of the three-phase winding and the insulation resistance to the ground (to the chassis) with a 500v insulation shaker. The insulation resistance of the motor that has been stored for a long time should be more than 0.5 megohm, and it can be used. More than 0.1 megohm and less than 0.5 megohm indicate that the motor has been damp, and it can be used after drying. Very low insulation resistance indicates that the insulation has been damaged.

3. Rotating the motor rotor should be easy and free, and there should be no noise or friction, indicating that the bearing and air gap are normal.





2. Use a multimeter to test the motor

1. Resistance to ground (use ohm gear position): The insulation resistance between the motor winding (three-phase) and the shell is generally required to reach 2M or more. It can be lowered as appropriate when used in humid, acid-base and other environments. Not less than 0.5M.

2. Resistance between phases (in ohm mode): The insulation resistance between windings of different phases is generally required to be above 2M. It can be lowered as appropriate for use in humid, acid-base and other environments, generally not less than 0.5M.

3. Three-phase resistance value (use the low gear of ohm gear): the resistance value of the three-phase winding, which requires the resistance value of the three-phase winding to be roughly balanced (measured with a digital meter to get accurate data, different motor capacities require different requirements, generally The requirement does not exceed 2%).

3. How to detect the quality of the motor?

1. Shake the meter, just shake the meter at 500V. The insulation resistance of the wires on the three terminals to the motor shell should be above 0.5M ohm, which means there is no short circuit to the ground.

2. Multimeter measurement: Measure whether the resistance between the three phases of A/B/C is equal or not. It should be about the same. If there is too much difference, it can be turned, but it will not last long. Remember that the larger the motor, the smaller the resistance! But not all three phases are 0 ohms, unless you are very large, such as a motor above 50KW! Remember that if it is a speed-regulating motor, the resistance of the 6 terminals can be different!

3. Check the bearings and fans. Generally, the motor will be completely replaced if it is wrapped around it! Because sometimes the bearing locks will burn the motor!

4. The no-load current of the motor is generally 10% to 50% of the rated current. Sometimes the no-load current of the motor is still zero!

5. When the motor is running at the rated current, it is running at full load, and the output power is basically 100%. The running current is small, indicating that the output power of the motor becomes smaller, and it is running at light load.

6. There is no three-phase power, find a starting capacitor for the washing machine, and it can also be switched on 220V!

Fourth, how to detect the quality of a single-phase motor?

Use a 500V megohmmeter to measure the insulation resistance between the motor winding and the casing, and it should not be less than 0.5 megohm; use a multimeter to measure the leads of the windings, and there is no disconnection; the above all meet the requirements, and the motor is good.

It is more convenient to use a pointer multimeter to detect the quality of the capacitor (there are also digital meters with capacitance files, which can be directly measured).

Set the multimeter to the 1K or 10K resistance range, measure the 2 leads of the capacitor, and then turn the needle to the right quickly and then slowly return to the left. The capacitor is good; if it is always to the right, the capacitor is broken down; if the pointer does not move, the capacitor is broken. Internal disconnection or no capacity. Using this method can only judge the quality of the capacitor, and the size of the capacity needs long-term experience accumulation to estimate.

5. How to detect the quality of the ventilation fan motor?

There is a multimeter. Use the resistance file (X10) of the multimeter to measure the three wires of the motor. They should be interoperable, but the resistance values are different, red (connected to the live wire) and black (connected to the neutral wire) + blue (connected to the capacitor) And black (connected to the neutral wire) = the resistance of red and blue and black is greater than the resistance of red and black. Generally, it is possible that red and blue are connected (there is resistance), and if black is not connected to red and blue, then it is inside the motor. If the overheating protection is burned out, replace if there is a replacement, don’t need it if there is no replacement, just skip it.

6. How to detect the quality of the two-speed motor of the lathe?

1) The three-phase resistance value (U1, V1, W1) of the angle measurement connection should be the same.

2) When measuring the three-phase resistance value of the double star (measure U2, V2, W2, U1, V1, W1 short circuit), the three-phase resistance value should be the same.

3) The ground insulation resistance of the motor windings should be greater than 5 megohms.

Seven. How to detect the quality of the air conditioner fan motor?

The motor has three wires, two sets of coils, one set is the starting coil, one set is the running coil, and the coil connected to the capacitor is the starting coil. The resistance value is a bit larger than the running coil. The two sets of coils must have resistance values with a multimeter. , About 200 ohms ---400 ohms. 6. How to detect the quality of 36V and 48V brushless controllers for electric vehicles? Turn on the electric door lock, and the 48V battery DC is input to the controller through the electric door lock cable, one way is sent to the ③ pin of U6 through R3, R13, R4, etc. for battery undervoltage detection, and the other is sent to U13, U14, U15 output + 15V and +5V supply power to IC and final stage driver. The pins ⑨ and ⑩ of the single-chip microcomputer PICl6F72 are connected with a 16MHz crystal, and the pins are connected with R13 and C25 to form a reset circuit, the electric door lock is unlocked, and the single-chip microcomputer enters the initialization self-check state after it is powered on. It mainly detects:

  1. The battery undervoltage detection circuit composed of R3, R73, R4, R11, C2l, etc. (typical value U6 pin 3 inputs 3.8V).

  2. The final current detection and overcurrent protection circuit composed of R5, R6, U1, etc. (the ⑦ pin of the normal value Ul outputs 0V, and the ① pin outputs about 3.6V).

3. Turn the reset signal (input the low level of about 0.8V to the ⑥ pin of the normal value U6).

4. Brake reset signal (normal value U6 pin ⑦ input 4.8V high level).

5. The phase signal of the brushless motor detected by the motor Hall element (at least one Hall wire input is 4.1V under normal conditions, and the others are 0V).

The status after self-check is displayed by LED2. The following is the reference value (the specific display is related to the program design of the microcontroller).

flash l stop l-self-check passed normally

flash 2 stop l--undervoltage

flash 3 stop l--LM358 failure

flash 4 stop 1-motor Hall signal failure

flashes 5 stop l-down tube failure

flashes 6 stops l--upper tube failure

flash 7 stop 1-over current protection

flash 8 stops l--brake protection

flash 9 stop 1-the hand is disconnected from the ground wire

flashes 10 stops 1-the handle signal and the handle power cord are shorted

flashes l stop 11-the handle signal is not reset when power is on

I detect the quality of DC motors, which can be divided into static detection and dynamic monitoring.

Static detection:

1. A megohmmeter is required to measure the insulation resistance (between the armature and the excitation; between the motor, the excitation and the housing);

2. Observe the commutator, it is smooth without scars;

3. Check the degree of wear of the carbon brushes and whether the "small braid line" is loose or damaged;

4. Check whether the internal connection with the output lead terminal is firm.

Dynamic detection:

1. Judgment of geometric centerline, judgment of voltage symmetry under the same given forward and reverse directions;

2. There is a problem when the no-load current is judged to be greater than 10%, and the normal no-load current should be less than 10% to be normal;

3. Run to the rated speed with no load, stop freely after power failure, check the operation of the motor's drive train bearing and determine whether the dynamic balance meets the requirements. There should be no obvious vibration and noise in the motor during taxiing. First look at the excitation current and armature current. If it is not large, you can be sure that the motor coil is not broken. Check whether the mechanical part is flexible. If there is no problem, check the driver. 1. Of course, the higher the insulation resistance, the better. Generally tens of megohms is normal, but for some southern regions in humid seasons, a few megohms can also operate; in special cases 500K to 1 megohms, it can also operate, but it cannot operate normally, but to improve the insulation resistance of the baking machine , It is low-voltage no-load operation. (This is for low-voltage motors below 400V)

4. As far as experience is concerned, the dynamic balance test of the motor adopts no-load, high-speed, and then power-off and coasting. You can judge. However, if the dynamic balance is corrected, it must be carried out on the dynamic balance machine. There are many ways to detect and adjust the geometric centerline of a DC motor, and there are also wonderful descriptions in the past essence posts here. It seems to be 3 or 4 kinds. I generally judge and adjust the position of the geometric centerline by checking whether the forward and reverse rotation speeds are consistent through forward and reverse conversion under the same setting. At this time, the given speed should not be too high, just 10% of the rated speed.