Repair Of Broken Bar And Engine Cover Of Miniature DC Geared Motor

In the long-term use of the micro speed regulating motor, the squirrel cage may be damaged and the hood may fail. What should I do if it is urgent and can be repaired by myself?

Question 1: How to judge the broken bars of the squirrel cage?

After the cage rotor is disconnected, no-load operation is usually normal, but under load, the motor speed decreases, the stator current increases, the motor vibrates, the temperature rises, and it is accompanied by abnormal noise. The greater the load, the more broken bars, and the more serious the above phenomenon.

Alternative: Find a motor rotor with the same casing number and the same iron core, and replace it with the faulty motor installed. All of the above failures can be eliminated by the same load test. This proves that there is something wrong with the rotor cage of this motor.

Power-on method: connect the low-voltage alternating current to the single-phase winding of the motor with a single-phase voltage regulator of appropriate capacity. The voltage regulator is gradually boosted from zero, and the current is measured with a clamp-on ammeter. When the current rises to about 1/2 of the rated current of the motor, stop boosting. Then slowly turn the motor shaft by hand and observe the pointer of the clamp ammeter. If the pointer does not move or wiggle slightly, the rotor is intact. If the pointer swings periodically and a lot, it indicates that the rotor cage has a broken bar.

Second question: motor fix after "and hood"

After the wound motor and headband come out of the short circuit, the end of the wire usually burns for a while and the length of the wire can be repaired. The specific method is as follows:

Use 1-2 250W IR bulbs to partially soften the rotor end to release the gun, remove the copper foam, then slightly bend one end of the fired (flat) copper wire (for soldering). The length of wire can be silver soldered or soldered. During the welding process, care should be taken to protect the windings so as not to burn out (protected with wet asbestos cloth (rope)). Flatten the seam after welding. After straightening the copper wire, wrap it with a layer of glass tape, apply insulating paint, and blow dry with an infrared light bulb. With the wire in its original position, place a green film underneath, then cut off the excess copper wire, place and solder the sleeve. Paint and dry on site. The copper shell is applied to the hood and made to original size. Before production, copper sheets should be tinned.

Usually, soft windings have to be baked before the wire can be removed. However, with larger capacity motors it is more difficult to soften and disconnect the wires, so the old windings can be removed by:

Use a flat scraper to remove one end of the winding so that the cut is flush with the notch. Cut the other end of the winding with metal scissors, then drive the enameled wire into the groove with a suitable copper rod to clear the groove. The wires in each slot can be punched together if the copper rods are suitable and done correctly. When using a flat shovel, be careful not to touch the stator core.

When the pipeline is dismantled by the above method, the drying process before dismantling can be omitted, which saves time and electricity, and the dismantling is relatively labor-saving. But this method is suitable for motors below 7.5KW. Due to the small casing of the micro-speed motor, it is inconvenient to use a flat shovel to operate.