Common fault inspection and treatment of the hotte

Inspection and treatment of common faults of drum generator

1 The failure of the generator to generate power is mostly caused by the disappearance of remanence or internal wiring errors. The following methods can be used to check:

1) check whether the fan belt tightness is appropriate. If it is too loose, the generator speed will be insufficient, resulting in weak power generation

2) check the coordination between commutator and carbon brush. It has been proved that most generator faults occur here. Remove the dust cover and focus on the following aspects:

① observe the surface of the commutator. If there are carbon black ablation marks or oil stains, it will directly affect the current output. It should be polished with 00 sandpaper and wiped with a cleaning cloth dipped in gasoline. If there is a glossy purple gray oxide film, it can not be worn out because of its good wear resistance

② check the combination pressure of carbon brush and commutator. Use your finger or screwdriver to pressurize the two carbon brushes. If the power generation is immediately normal, it indicates that the carbon brush spring is too soft or the carbon brush is excessively worn, and you should replace it with a new accessory. In case of transportation or field operation, iron wire can be used to lift the fixed end of the carbon brush spring and connect it with the wiring screw of the carbon brush holder as a temporary remedy

③ observe the spark between the carbon brush and the commutator to check whether they fit closely. Control the engine above medium speed, and then lap the armature and magnetic field terminal to increase the output current. At this time, there should be weak sparks between the carbon brush and the commutator joint surface. If there is a large arc spark, the carbon brush and commutator will burn out quickly, affecting normal power generation. At this time, you can pressurize the carbon brush with your fingers. If the spark is eliminated and the power generation is normal, it indicates that the bonding pressure of the carbon brush is too small; If the spark still cannot be eliminated, it indicates that the commutator surface is out of round, the mica protrudes, or the armature coil is partially short circuited, powered off, and touches the iron

3) if the above inspections are normal and still do not generate electricity, the wiring and internal conditions of the generator can be checked by the fire wiping method. When checking, the year-on-year decrease is about 45%, remove the regulator, connect the armature terminal and the magnetic field terminal with a wire to collide with the battery terminal respectively, and observe the spark condition

there is also an obvious drop phenomenon. There are four phenomena: ① blue and white small sparks, indicating that the excitation circuit is well connected. ② No spark indicates that the excitation circuit is open circuit. At this time, connect the magnetic field wire head to the battery terminal, and then remove the column head of the magnetic field terminal on the generator to collide with the chassis. If there is spark, it means that the wiring is intact, but the excitation coil is open circuited; If there is still no spark, it indicates that the wiring is open circuit. ③ If a small dark red spark is emitted, it indicates that there is a poor contact somewhere in the excitation circuit. This problem is often caused by false welding. ④ A strong spark accompanied by a sound indicates that the excitation circuit touches the iron. At this time, the wire head of the magnetic field terminal on the generator should be removed, and the wire head of the magnetic field at the regulator should be collided with the battery terminal again. If there is a spark, it is proved that the magnetic field coil touches the iron

there are also four phenomena when the wire end of the armature is collided with the battery terminal:

① blue and white sparks are emitted, indicating that the armature line is well connected

② no spark, indicating that the armature circuit is open circuit. At this time, the armature wire head should be connected with the battery terminal. After the wire head on the motor armature terminal is removed, it collides with the damaged sample removed from the housing. If there is spark, it indicates that the wiring is intact, and it proves that the carbon brush lead on the armature coil or its terminal is open circuit. If there is still no spark, it indicates that the wiring is open circuit

③ a small blue and white spark indicates a poor contact somewhere in the armature line

④ sends out strong white sparks, indicating that the armature line touches iron somewhere

2. Check for abnormal power generation of generator

1) grounding and fire scratch method: stabilize the engine speed above the medium speed, then temporarily short circuit the armature magnetic field wire post of the generator, and touch the armature wire post with the chassis instantly with a screwdriver. If there is a strong blue and white spark, it indicates that the power generation is normal; If there is a small dark red spark or no spark, it means no power generation. At this time, tighten the fan belt a little, remove the armature and magnetic field terminal, go up to the wire end of the regulator, and then try again according to the above method. If the spark is normal, it means that the belt is too loose or the armature and magnetic field wiring to the regulator touches iron. If there is still no spark, the generator is faulty. The grounding ignition method is simple and easy, but it can not accurately detect the fault of insufficient power generation of the starting motor

2) no load voltage method: first, adjust the tightness of the fan belt appropriately, remove the armature and magnetic field terminals leading to the regulator, and then short circuit the armature and magnetic field terminals on the generator with wires. In the positive grounding system of the battery, connect the negative probe of the DC voltmeter (550V) to the armature or field terminal of the generator. Connect the positive probe to the housing and observe the reading of the probe. The rotor speed of 220 watt generator is 1250 rpm, and the voltage should be 12.5 v. When the speed reaches 2800 rpm, it can reach 35 volts. The 150 Watt generator can reach 27 volts at 1650 rpm. If the voltage value is more than 3 volts lower than the required value, the generator is abnormal

3) motor test method: after the generator armature and field terminal are shorted, connect an ammeter in series to the negative pole of the battery, and the positive pole of the battery is connected to the motor shell. If it is checked on the locomotive, the three terminals of the regulator should be short circuited with wires. After the circuit is connected, the generator rotates smoothly immediately. The current of 150 Watt generator is not more than 6.5 a, and that of 220 watt generator is not more than 5.5 a. If the generator does not turn, it means that the motor is internally short circuited, disconnected or connected incorrectly; If the sound is normal and the current is large, it indicates that there is a short circuit between the excitation coil or armature coil; If the current is normal and there is noise, it indicates that the bearing is lack of oil; If the current is large and there is noise, it indicates that the bearing clearance is too large, resulting in rotor sweeping or friction due to improper assembly of some parts; If the sound is normal but the current is small (34 A), and there is a large spark in the commutator, it indicates that the armature winding is partially open circuit. When using this method to check the fault of the generator, we should pay attention to two points: ① the current and sound are normal, and sometimes it still can't generate electricity, because the magnetic pole core of the generator can't be magnetized. When the iron core of the magnetic pole is of poor quality, or the magnetic molecules are seriously disordered due to violent impact, the magnetic field established by the excitation coil under the voltage of 12 volts cannot magnetize the iron core. In this way, the iron core has no remanence and cannot generate electricity. At this time, the magnetization voltage should be doubled. ② The speed of the DC generator during the DC motor test is directly proportional to the power supply voltage and inversely proportional to the magnetic flux of each pole. Therefore, when the generator is running, if the magnetic field wire is removed, the magnetic field will suddenly decrease, and the motor speed will suddenly increase. At this time, due to the weak magnetic field and the low back EMF of the motor, the current to the armature increases a lot, so the magnetic field line should not be disconnected when doing this test

3. Overheating of generator during operation

overheating of generator is a common fault, which is mostly caused by the following reasons:

1) excessive output current. Usually, the voltage regulation in the regulator fails, and the exciting current is too large, which increases the output current. It may also be due to the short circuit of the armature and field terminal of the generator, or the artificial forgetting to remove the short circuit of the armature and field

2) short circuit between turns of exciting coil and armature coil

3) because the bearing clearance is too large, the armature iron core and magnetic pole may rub against each other, and the bearing grease may also be used incorrectly. Because the rotor speed is very high, high temperature resistant sodium base or compound calcium base grease should be used. Ordinary grease is easy to flow out and deteriorate at high temperature, resulting in bearing heating

4) strong sparks between carbon brushes and commutators will also cause overheating of armature coils and commutators. When the temperature exceeds the melting point of the solder, the solder at the joint is melted, and the solder is thrown out under the centrifugal force of the high-speed rotation of the rotor

4. After the generator is used for a long time, the joint of the inner and outer rings of the bearing with the cold charging well is often worn. In case of emergency, the following methods can be used for repair:

1) weld a thin layer of solder on the outer ring of the bearing or the shaft diameter of the rotor, and increase the outer diameter of the bearing or shaft diameter

2) treatment with throwing method. One pole of the battery is connected to the bearing, and the other pole is pitted with the outer ring of the bearing intermittently through the carbon rod. The large instantaneous current wraps the outer ring out of the pit, thus increasing the outer diameter. The outer diameter of the shaft can also be increased by the same method

3) in the absence of the above conditions, use a punch to punch several hemp pits out of the end cover seat hole and journal for temporary first aid