Analysis of fault causes of short circuit of vibration motor winding

The vibration motor uses centrifugal force generated by high-speed rotation of shaft and eccentric block to produce exciting force. It has been widely applied in hydropower, thermal power, building, building materials, chemical industry, mining, coal, metallurgy, light industry and other industrial sectors. So what is the cause of the short circuit of the machine during the operation of the machine? How are we going to solve this problem again? What we share with you today is the cause and solution of the fault of the short circuit of the vibration motor winding.

 

First of all, the main reason for the failure is due to the insulation failure caused by too much current of the vibrating motor, too large supply voltage, single phase operation, mechanical bruise and poor manufacturing.

 

Second, what is the winding? Winding is part of the motor. Aging, wetting, heating, erosion, foreign matter intrusion and external force impact will cause damage to the windings. Motor overload, undervoltage, overvoltage and phase running can also cause winding faults. Windings faults are usually divided into winding grounding, short circuit, open circuit and connection error.

 

Now the fault phenomenon, the cause and the method of inspection are explained separately.

 

A: Windings grounding

 

The grounding caused by touching between winding and iron core or the damage insulation of the casing.

 

1. Failure phenomenon

 

The electric housing is charged, the control line is out of control, and the winding is short circuited by heating, which causes the motor to be unable to operate normally.

 

 

2. The causes

 

Moist decreases the winding insulation resistance; long-term overload operation; harmful gas corrosion; metal foreign matter intrude into winding and makes internal insulation damage; the winding insulation is damaged when rolling, and touched the of stator; the winding end touch base cover the stator and rotor friction caused by insulation; burn; lead wire insulation damage and shell together; over voltage (such as lightning). Insulation breakdown.

 

3. Inspection method

 

(1) The observation method. Through the visual winding ends and the line slot insulation for any damage and observe the blackened traces, if it is to take place.

 

(2) The method of multimeter inspection. Use the multimeter low resistance gear check, the reading is very small, it is ground.

 

（3）Tramegger Method. According to the different levels of insulation resistance with different tramegger measure each group resistance, if reading is zero, said the winding grounding, but to motor insulation damp or by accident and breakdown, to judge on the basis of experience, generally speaking pointer in the “0” place without swaying timing can think it has certain the resistance value.

 

(4) Light test method. If the test light is on, the windings are grounded, and if a spark or smoke is found somewhere, it is the grounding fault point of the windings. If the lamp is light, the insulation is grounded. If the lamp is not bright, but the test rod is connected to the ground, the spark also appears, indicating that the windings have not been penetrated, but are seriously dampened. Also available in the mouth of the hardwood shell tapping edge knock to a place, a light one out, that current when the broken, then it is take place.

 

(5) The method of current burning. With a voltage regulating transformer, after the power supply, the place is quickly heated, the insulation is the place where the smoke is the place. Special attention should be paid to the fact that a small motor must not exceed two times the rated current, and the time does not exceed half a minute. The large motor is rated at 20%-50% of current, or gradually increases the current, and the power is cut off immediately when the location is just smoked.

 

(6) The group elimination method. The burning of the burned copper wire is fused with the iron core for the place in the core and the burning of the core. The method used is to divide a phase winding of the ground into two halves, and by analogy, to find the connection place at the end.

 

In addition, there is high voltage testing method, magnetic exploration method, vibrating method and so on, here is not introduced one by one.

 

4. Treatment method

 

(1) The grounding should be dried first when the windings are dampened, and when it is cooled to about 60 - 70 degrees C, the insulating paint is poured and then dried.

 

(2) When the end of the winding is damaged, the insulation is retreated, painted, and then dried at the ground.

 

(3) Windings to place in the slot should be rewound, winding or replace part of the winding element.

 

Finally, different megabytes are used to measure and meet the technical requirements.

 

B:Short circuit of winding

 

Due to the over current of motor, power supply voltage variation, single-phase operation, mechanical bruise, and poor manufacturing, the insulation damage occurs. There are sub turn short circuits, short circuit between windings, short circuit between poles, and interphase short circuits between windings.

 

1. Failure phenomenon

 

The uneven distribution of magnetic field and the unbalanced three-phase current make the motor vibration and noise aggravate when running. When the motor is serious, the motor can't start, but the short circuit current in the short circuit leads to the rapid heating of the coil and the burning.

 

2. Causes

 

Motor overload for a long time, the aging loss of insulation; wire insulation damage caused by damp; winding insulation resistance decreased due to insulation breakdown; and the end of the interlayer insulating material is not damaged or plastic pad good; end connecting line insulation damage; overvoltage or lightning insulation breakdown; the rotor and the stator winding end Department of friction between the insulation damage caused by metallic foreign bodies into the interior of the motor; and too much oil.

 

3. Inspection method

 

(1) External observation method. Observe the junction box, the end of the winding is not burnt, the windings are dark brown after overheating, and have a bad smell.

 

(2) The method of detecting temperature. Run for 20 minutes (when it is found to be abnormally should stop), and use the back of the hand to see if the parts of the windings exceed the normal temperature.

 

(3) The method of electrifying experiment. By measuring the current meter, if the phase current is too large, it shows that the phase has a short circuit.

 

(4) Bridge inspection. To measure the DC resistance of the windings, the general difference should not exceed 5%. If the resistance is over, a phase with a small resistance has a short circuit fault.

 

(5) Short circuit reconnaissance device. When the measured winding has short circuit, the steel piece will produce vibration.

(6) Multimeter or megabyte method. The insulation resistance between any two phases windings is measured. If the reading is very small or zero, it is indicated that there is a short circuit between the two phases windings.

 

(7) Voltage dropping method. The three windings are connected in series with low voltage secure alternating current, and a group of small reading has short circuit fault.

 

(8) Current method. When the motor is running at no load, the three-phase current is measured first, then it is measured and compared in the two phase exchange. If there is no change with the power supply, a large current phase winding will be short circuit.

 

4. Short circuit treatment method

 

(1) The short circuit point is at the end. The insulating material can be separated from the short circuit point, and the insulation line can be rewrapped, and then the paint is dry.

 

(2) Short circuited online slot. After the softening, find the short circuit point repair, re-put into the line slot, and then dry the lacquer.

 

(3) Cut off all short lines when the short circuit turns less than 1/12, and connect the conduction part to form a closed loop, so that the supply is urgent.

 

(4) Winding short-circuit point turns over 1/12, to be removed to rewind.

 

C: Winding circuit breakage

 

Due to bad welding or using corrosive flux, welding and not clean, it may cause the pot welding or loose; mechanical stress or collision coil short circuit, short circuit and ground fault also lead can be burned, one or several wire short circuit in a few wires and burned in, several other wires due to current increases with the temperature rising caused by heating and winding circuit. In general, it is divided into the end of phase winding, short circuit between switches, circuit breaker in parallel branch, a number of wires and a circuit breaker in the burning, and a rotor broken cage.

 

1. Failure phenomenon

 

The motor can not start, the three-phase current is unbalanced, abnormal noise or large vibration, temperature rise exceeds the allowable value or smoke.

 

2. Cause

 

(1) Break or make manufacture quality problems during maintenance.

 

(2) Winding of each element and pole (phase) group and winding and lead wire connection head poor welding, long running hot de-soldering.

 

(3) The windings are damaged or broken by mechanical and electromagnetic forces.

 

(4) Short circuiting and grounding of the interphase or interphase cause serious burning or fuse of the winding.

 

3. Inspection method

 

(1) The observation method. Breakpoints occur mostly in the winding end, check whether there is breakpoint and de-soldering point.

 

(2) The method of multimeter. The resistance profile of the "Y" type connection rod with a table in the shape of "Y" on the central point, the other one is connected sequentially in three-phase winding end, infinite phase for the breakpoint; "delta" type connection short connection, were measured in each winding infinity is, the circuit breaker point.

 

(3) Light test method. With the former method, such as a circuit breaker is not bright.

 

(4) Megabyte method. A phase in which the resistance tends to be infinitely large (that is, not zero) is a circuit breaker.

 

(5) The ammeter method. When the motor is running, it uses the ampere meter to measure the three-phase current. If the three-phase current is unbalanced, and there is no short-circuit phenomenon, there will be some short open circuit faults with a smaller current.

 

(6) Bridge method. When a phase resistance of the motor is larger than that of the other two phases resistance, it is indicated that the phase winding has some breakdowns.

 

(7) Current balance method. For the "Y" type connection, the three-phase windings are connected in parallel, the low voltage high current alternating current, if the current in the three-phase winding is greater than 10%, one small current circuit breaker; for delta connection, the first one contact of stator winding apart, then gradually is in low voltage and high current, the current small one phase circuit breaker.

 

(8) Checking the cage reconnaissance device. When the rotor is broken, the readings of the milli voltmeter should be reduced when the rotor is checked.

 

4. Circuit breakage processing method

 

(1) The circuit breaker in the end, after connecting welding, insulation package, sleeve insulation tube, binding, and drying.

 

(2) Use new winding to replace the old winding, the short circuit and the grounding of the windings, which cause the serious burning of the winding.

 

(3) Emergency treatment is done for breakpoints in a slot with a small number of breakpoints. The breakpoint is found by grouping elimination method, and is connected to the broken ends of the windings and used after insulation is qualified.

 

(4) the cage shaped rotor can be repaired by welding method, cold connection method or strip changing method.

 

To sum up, the main reason for the malfunction is due to the excessive vibration motor current, excessive supply voltage, single-phase working, mechanical bruise, poor manufacturing and so on. Therefore, we should check all the preparations before running the machine, and we should always pay attention to the change of machinery in the course of operation.