printing equipment2

① General knowledge of electrical maintenance

In the daily repair of printing equipment, the electrical part accounts for a large proportion. With the continuous development of printing technology and equipment, the degree of automatic control is higher and higher, and the control system is also more complex. Therefore, electrical maintenance personnel are required to have high technical skill level and quality, understand computer principle and be able to operate. For the electrical personnel of printing maintenance, the following points should be paid attention to in the daily maintenance work:

a) Carefully read the electrical schematic diagram and relevant documents of the equipment, and master the electrical principle and control system principle of the equipment in principle. Find out the location of electrical components, wiring, pipe layout, number and direction.

b) For the faults of machinery and equipment, carefully analyze the possible parts of the fault, find the components and circuits that may cause the fault according to the electrical schematic diagram and wiring diagram, diagnose and eliminate them one by one.

c) In electrical repair, first check the power supply voltage? Whether the current is normal, whether the air pump pressure meets the standard, whether the oil pressure of the lubrication system meets the standard, etc. if necessary, the load can be disconnected, which is helpful to judge whether the mechanical overload is caused

Electrical fault or protection caused by load.

d) The web offset press adopts PC for automatic control, which brings a lot of convenience to the troubleshooting of electrical faults? Generally, there is a LED in the control cabinet for fault prompt, and the fault position can be found according to the prompt? In more advanced equipment, you can first find the prompt on the console display screen, or "talk" with the industrial computer in the control cabinet with a laptop to find the system with fault? Parts, and then eliminate them one by one?

e) Common electrical faults can be summarized as follows: fuse damage, contactor and relay contact damage, loose wiring and poor contact, failure of button and limit switch, failure of control switch at a certain position in safety protection system, failure of optoelectronic detection in tension control system and paper breaking system, air leakage and damage of solenoid valve, etc.

f) Motors are the source of power in printing equipment. The common faults of DC motors and AC motors are briefly introduced below.

There are two common faults in DC electric operation: mechanical and electrical. Mechanical faults mainly include bearing heating, motor vibration, collision between armature and stator core, abnormal noise, etc. It is generally caused by the rotation of the armature. During the inspection, rotate the armature manually to observe whether the armature collides with the stator, and judge whether the vibration is caused by the motor itself or by the poor transmission device. The motor is less likely to vibrate due to its poor dynamic balance. It often vibrates due to the poor concentricity of the transmission device. This phenomenon is easy to cause the motor bearing damage and even the armature output shaft deformation.

The most common electrical fault of DC motor is the spark between brush and commutator. During normal operation, the spark between brush and commutator is light blue, weak and dense. The contact surface of brush is smooth and bright, and a layer of reddish brown oxide film will be formed on the surface of commutator. When the motor operates abnormally, the spark size and color will change. When the fault is slight, the spark will appear yellow red and bright, and the surface of the commutator will be black and burned. If the spark is serious, a large number of red and green sparks will be sprayed, mixed with flash fire and accompanied by rattling. If the machine is not shut down in time for inspection, the commutator, brush and brush holder will be burned out soon. When the brush position deviates from the geometric center line, serious sparks may occur in case of open circuit and short circuit in the armature winding. In addition, the failure will be caused by the inconsistent brand and performance of the brush, too large and too small brush pressure, poor brush grinding, too little contact area and other reasons.

The mechanical fault of AC three-phase asynchronous motor is basically the same as that of DC motor. Here is a brief introduction to common electrical faults. First, single-phase operation fault, that is, one phase of the three-phase winding of the motor is disconnected. At this time, the motor torque decreases significantly, the speed slows down, the sound is abnormal, and the motor will burn out due to serious heating for a long time; Second, the motor is seriously heated and even gives out paste odor. This fault may be caused by too heavy load or too low or too high power supply voltage.