In the motor repair will encounter a variety of situations, such as to take a reasonable repair method, in the repair to avoid detours, to achieve a multiplier effect. Will be the routine maintenance work experience and experience, summarized as several practical methods of motor repair, including the motor insulation resistance is reduced, the stator winding slot has a grounding point, winding inter-turn short circuit, cage rotor broken bar, between the motor and Head cover blasting ", the old winding removal, rotor journal and end cap bearing chamber wear and other issues of treatment and repair methods for reference.

 

Now the motor maintenance, often meet the problem summarized, introduced in the repair work of several practical methods.

 

1 After the cover is installed, the motor insulation resistance is reduced

 

Cage-type motor repair is not installed before the end of the cover, the winding on the chassis insulation is good. After installation, the insulation resistance is reduced. This can determine that the fault occurred at both ends of the winding. Resulting in the reasons for the reduction of insulation resistance, may be enameled wire on the film has a local break or winding mode to make the end of the winding longer. After the end cap is covered, the inner wall of the end cap is close to or comes into contact with the fault point, so that the winding insulation resistance is reduced.

 

To rule out this failure, first determine the fault at which end of the motor. Judgment method is: first install an end cap, with 500V insulation resistance meter measured winding insulation resistance, such as very low, then this side of the winding fault exists. Then, remove the head cover, and then install the other end of the cover, measuring the winding insulation resistance, such as low, then the other side there is a fault there. In the demolition, loading the end of the process, the rotor can not be installed.

 

To determine the fault side, the general end of the winding a little shape, and coated with some insulating paint can be, if not solve the problem, you can easily outside the end of the winding end of the end of the cover with a layer of thin film green shell paper, Generally can be eliminated.

 

2 stator winding slot has a grounding point to find and deal with

 

Stator winding slot in the ground, generally occurred in the slot. As the tank insulation paper in the slot pad bias, damage, or in the slot due to off the assembly line, crossed inadvertently, the enameled wire into the slot insulation paper below, or when the groove wedge into the slot insulation paper, Causing ground fault.

 

For this failure, first of all to determine whether the motor winding moisture, if it is damp on the motor baking, the result is invalid, then determine the ground fault.

 

Find the location of the method has the following points:

 

(1) carefully check the lead and groove at both ends, found that the outlet is intact, slot at both ends of the slot insulation are no damage, the motor inside and outside is very clean, dust and oil everywhere, indicating that the grounding point in the tank.

 

(2) Unwrap the Y-type connection points of the stator windings, measure the relative insulation resistance, and detect the phase of the ground fault.

 

(3) with a single-phase voltage regulator, the output of the phase of the phase connected to the ground fault phase of the end of the lead-out line, the zero line connected to the motor chassis, and then the regulator from zero to boost, Smoke, which is immediately the regulator output voltage will be zero and cut off the power, smoke is the ground point. The entire operation should pay attention to safety, the motor should be placed on an insulation pad, cut off the power before the person can not touch the motor.

 

The method is: the ground groove of the wedge carefully removed, and then the motor into the oven heating, baking soft winding, and then carefully remove the inside of the slot, check the wire insulation. Insulation is broken to paint, dry, and then re-placed in the tank slot insulation paper, and then remove the line into the tank, into the groove wedge, winding dipping, drying.

 

If you find the enameled wire has been blown, to the two broken head were pulled to the end of the winding, and then find a wire diameter of the same enamel into the tank, the two ends of the winding wire. Joints to twist soldering, painting, drying, and then set the insulation sleeve. When bundling the end, pay attention to the bundled joints.

 

Judgment of Inter - turn Short Circuit Fault of Stator Winding

 

Stator winding inter-turn short circuit fault, generally by measuring the three-phase winding DC resistance to determine. But the larger capacity of the motor stator winding DC resistance is very small, coupled with instrument accuracy and measurement error and other relations, not easy to come to the correct judgments, but can be used to determine the following ways.

 

Do not break the motor, with a capacity of the appropriate single-phase autotransformer, from zero to gradually boost, to one of the low-voltage AC power. At the same time, with a clamp ammeter to measure the current, the current rise to the motor rated current of about 1/3. And then stop the boost, with a multimeter to measure the other two-phase induced voltage, if a phase has a short-circuit between the inter-turn fault, its induced voltage is lower than the other. And then exchange the same phase power, with the same method to measure the other two-phase induced voltage. Depending on whether the induced voltage is the same, it can be judged whether there is a turn-to-turn short circuit fault. Stator turn short circuit fault, in the maintenance of the general need to replace the motor winding.

 

4 judgment of rat cage

 

Cage rotor broken bar, the general is no-load operation is normal, but with a load, the motor speed is reduced, the stator current increases, the motor vibration, the temperature increases, and will be accompanied by abnormal noise. The greater the load, the more broken, the more serious the above phenomenon.

 

To determine whether the broken method is as follows:

 

(1) power method: with a capacity of the appropriate single-phase voltage regulator, to the motor-phase winding into the low-voltage alternating current. The regulator slowly from zero to boost, while measuring current with a clamp ammeter, so that the current rise to the motor rated current of about 1/2, stop the boost. And then slowly turn the motor shaft, observe the pointer ammeter pointer. If the pointer does not move or slightly swing, indicating that the rotor intact, if the pointer cyclically swing, and the swing range is large, then the rotor rod cage broken bar fault.

 

(2) alternative method: is to find a motor with the same seat, with the heart of the motor rotor, replace the installation of this fault on the motor. With the same load test, the failure to eliminate all. Thus proving that there is a problem with the rotor rod cage of this motor.

 

5 between the motor "and the head of the blasting" after the repair

 

Winding motor and the hood between the breakdown after the short circuit, the general will burn a thread, repair can be used to take a long way, the specific approach is as follows:

 

With 1-2 250W infrared light bulb local heating softening the rotor end of the blasting, remove the copper foam, and then burn the (flat) copper wire slightly bent (to facilitate welding). Long wire can be used for silver welding or soldering. When welding, pay attention to protect the winding, so as not to burn (available wet cotton cloth (rope) protection). After welding the welding scar. The copper wire straightened, wrapped around a layer of glass ribbon, coated with insulating paint, with infrared light bulb drying. Wire into the original position, the next layer of thin film of green paper, and then cut off the excess part of the copper, set and headgear, soldering. Finally in the repair office painting, drying can be. And the head of the application of copper according to the original size of the production, should be made before the copper stamping.

 

And the head of the motor, the capacity is relatively large, demolition, equipment are more difficult, the method suitable for on-site repair.

 

6 motor removal of the old winding

 

Generally have to first bake the soft winding and then disassemble. But the larger capacity of the motor, baking soft and stitches are more difficult, it can be used to remove the old winding the following method.

 

Use a flat shovel to remove one end of the winding, and the incision is flush with the slot. The other end of the winding is cut with an iron scissors, and then the enameled wire in the slot is washed out with a thick copper bar. If the copper rod is suitable, the operation method is correct, the wires in each slot can be washed out together. When using flat shovels, be careful not to shovel the stator core.

 

With the above method of disassembly, you can save the pre-demolition of the baking process, save time, save energy, and dismantling more effort. However, this method is suitable for the capacity of 7.5KW below the motor, because the small motor or micro-motor chassis is small, the use of flat shovel inconvenient operation.

 

7 new brush grinding

 

DC motor or rotor is winding motor update brush. When the brush and the commutator surface perpendicular to the grinding brush method is: the commutator on the surface of a sandpaper, holding the same type of new brush along the commutator axial reciprocating friction, brush The grinding surface will soon be grinding out with the commutator surface coincides with the arc. First with coarse sandpaper, after the use of fine sandpaper. Grinding, hand brush to be positive and horizontal movement along the direction of the commutator axis, can not be skewed, reciprocating trip not too long. Care should be taken to prevent the brush powder from entering the armature and commutator grooves. After grinding, brush the brush into the brush, start the motor running for a few minutes, remove the brush check, the contact surface generally account for more than 80% of the total area of ​​the job, otherwise, to re-grinding until qualified.

 

When the motor brush and the commutator surface is not vertical, it is appropriate to use the following methods: the sandpaper on the plane, holding the brush by brushing the angle of grinding out a slope. And then put the brush into the brush grip, hand the motor rotor, so that the brush will be grinding on the slope of the bright spots, and then polished with bright sandpaper (knife can also be used to scraping). After grinding, then the brush into the brush grip, hand the motor rotor, the same will be grinding out bright spots, the area than the first large. So several times, the contact surface of the brush will be more and more, gradually forming a curved. Polished bright spots, each time do not polish too much, especially to the last time, be sure to be careful, as long as a little rub with a fine sandpaper can be. Such as wiping more, the contact surface but will become smaller. Practice has proved that this method of grinding the tilt of the brush, time is fast, the effect is good.

 

8 Rotor journal and end cap bearing chamber wear emergency repair

 

The specific methods and steps are as follows:

 

(1) first with ethanol or gasoline repeatedly washed to be Tu Tu Department.

 

(2) the ternary nylon ethanol solution heated into a transparent liquid, with a small brush dip this liquid thin coating at the wear, for a little wear and tear, may be appropriate to extend the heating time to make the solution a little thick and then coated. Generally need to be painted several times to achieve the required thickness so far, after the first painted, need to place about 3 minutes, to dry their own, to sticky hands can be painted the second time.

 

(3) after drying, can be heated method (temperature does not exceed 80 ℃, time is 0.5-1 hours), but also allow it to dry naturally (room temperature 20 ℃, placed in the ventilation room about 36 hours).

 

(4) wear within 0.10mm, coated dry, you can use. Wear more than 0.10mm, in order to ensure that the motor assembly, the stator and the concentricity, after the coating also need to be turning. (If the original bearing outer ring and inner ring size are within the tolerance range), the repair of the end bearing bearing chamber can be processed according to P6, such as repair the journal, you can press r6 processing.

 

Coated nylon solution to be completely dry, that is, with sufficient hardness and hardness, fully able to ensure that the requirements of motor assembly.

 

This method is only suitable for the amount of wear is not, only zero a few millimeters of the situation.