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2 The structure of the main motor The centrifugal refrigeration unit is mainly composed of the following parts: (1) evaporator; (2) compressor; (3) condenser; (4) energy saver; (5) venting system; Main motor; (7) lubricating device; (8) safety device; (9) energy control device.
The main motor is a special closed squirrel-cage three-phase induction motor. The special feature of the main motor is that the cooling of the motor is cooled by the refrigerant freon R. Due to the pressure difference between the condenser and the main motor, the liquid refrigerant enters the closed main motor cavity to cool the stator winding in the form of spray evaporation. The evaporated refrigerant gas and the residual liquid refrigerant flow back to the evaporator, and the main motor is long-term. Operates under conditions in which the refrigerant and the refrigerating machine oil coexist. Therefore, the main motor insulation structure has long been subjected to the gas phase and liquid phase refrigerant (R) and lubricating oil (refrigerating machine oil) and trace water, chemicals and the like. The stator winding of the motor is equipped with a temperature sensing element as a safety protection measure to prevent the winding from overheating. When the temperature rises to 80 e, the alarm will be issued, and at 105 e, the refrigeration unit will stop. The main motor stator insulation structure is specially designed to meet the requirements of the refrigeration unit under special conditions, and is also insulated with a special impregnating resin resistant to Freon.
Explosion-proof motor serial number Chemical name Trifluorochloromethane Difluoromethane Difluorochloromethane Molecular formula Appearance colorless, odorless, non-combustible, non-explosive toxicity Generally, non-toxic, non-toxic, R-toxic, slightly soluble in oil and The oily and oily is easily dissolved in any proportion, soluble in water, insoluble, and soluble in water. Other characteristics of the code are normal, liquid, stable, and generally have no corrosive effect, but in the case of electric spark, corona, etc., Cl, F are decomposed to form a hydride. It has a liquid specific gravity of 11 5 and is easily volatile. Its weight is 418 times that of air.
Critical temperature: 198e gas phase electrical strength: 101 8MVPm (three times nitrogen) is less harmful to the human body. Under normal circumstances, it has no corrosive effect. Only when the temperature reaches 400e or above and it is in contact with open flame, it will decompose toxic phosgene. If the content in the air exceeds 25% and 30%, it will also cause suffocation after two hours. A safe refrigerant, which is a water-insoluble substance, has a similar effect on metal and non-metal as R, and its leakage characteristics are similar to R. A methane derivative of a hydrogen atom, the evaporation temperature and the condensation temperature are lower than R under the same evaporation pressure.
The commonality of Freon: (1) insoluble in water, and strong infiltration; (2) soluble in oil, reducing the performance of lubricating oil; (3) when containing moisture, it is very corrosive to metals and non-metals; (4) It can dissolve a variety of organic substances and cannot be sealed with ordinary rubber.
The influence of Freon R on the insulation structure of the main motor. The commonality of Freon is that the strong penetrating power of Freon, which is highly corrosive when it is watery, and soluble in oil and dissolved in various organic matters, are directly related to the operation of the main motor. The service life of the insulation structure.
In general, it is relatively stable, but in the case of electric spark, corona, etc., Cl, F can be decomposed to form a hydride. R is easily dissolved in oil and grease. The lubricating oil (refrigerating machine oil) in the main motor is simultaneously brought into the inner cavity of the motor by R, and the rust, dirt and moisture generated by the main motor in the long-term operation are simultaneously applied to the main motor. Winding insulation will affect the insulation performance of the motor. The principle of action is the corrosion, softening and dissolution of the motor insulation caused by the decomposition products of freon, the oil-water mixture, etc., causing the phenomenon of motor insulation delamination, cracking, capillary phenomenon, adsorption of trace mixture, etc., resulting in a decrease in the insulation performance of the motor winding until Winding breakdown.
4Main motor maintenance It is well known that the use, maintenance and maintenance of the motor is directly related to the running effect and service life of the motor. Especially for the main motor of the refrigeration cycle compressor, maintenance and maintenance are more important. The main maintenance and maintenance measures are as follows: (1) The operator must be proficient in the instruction manual of the main motor and pass the training.
(2) The operator must be familiar with the structure and characteristics of the main motor, strictly abide by the operating procedures, avoid misuse, and be able to handle the occurrence of temporary accidents at any time.
(3) Strictly control the quality and performance specifications of Freon (R) and explosion-proof motor lubricating oil (refrigerating machine oil) injected into the main motor, and check the mixture regularly.
(4) Keep the main motor clean, monitor the running status of the main motor at any time, and make a record.
(5) Note: Absolutely avoid any voltage withstand test under vacuum.
5Main motor repair The refrigeration cycle compressor introduced by Daqing Petrochemical Company was put into operation in 1988. One of the main motors broke down in the stator winding in September 2002, causing a downtime accident and the stator winding repair was required.
Main technical parameters of 511 original main motor Rated voltage: 6 000V Rated power: 450kW Rated current: 5315A Pole number: 2p Heat resistance class: Class B cooling medium: Freon R working state: Continuous 512 stator winding surveying and mapping stator slot size and Number of slots, core length, stator winding structure and end dimensions.
Single glass polyester film wrapped with copper flat wire mica tape, polyester film with strong scales, powder mica with stator coil, anti-halation structure, 513 stator winding replacement, because the main motor is operated under special conditions for a long time, the replacement of the stator winding is required. The insulation structure shall have the following characteristics: (1) It shall have stable and reliable electrical properties, and maintain a sufficiently high insulation resistance and dielectric strength for a long period of time, in particular, it shall be able to withstand the high discharge and corona and other electrical corrosion caused by high field strength.
(2) It should have good thermal stability and ability to withstand mechanical vibration and various impacts.
(3) It should have the ability to withstand the effects of refrigerant (R) and refrigeration oil and trace moisture and decomposition products for a long time.
The newly designed insulation structure adopts a combination system of polyimide, mica and polyester imine. The insulating materials used are all screened by the fluorine resistance test and passed the insulation structure evaluation test.
Replace the stator winding test. The stator windings of the stator windings are made of white blank coils, and the analog coils are made according to the new insulation structure.
Test item Test conditions Unit test value Grounding resistance resistance Withstand voltage Through the dielectric loss electric strength 51412 machine test stator winding inlaid line, wire, after the whole solvent is impregnated with solvent-free resin vacuum pressure, immersed once. After the assembly of the whole machine, various types of tests were passed, and its electrical performance is shown in Table 4.
Test unit unit ground insulation resistance 2 500V megger The main motor operation of the stator winding is replaced by 515. After the main motor of the stator winding is replaced, the unit is calibrated to check the effect characteristics. When the compressor throughput reaches the rated value, The current of the main motor is 32A, which is significantly lower than the current of the main motor before repair. The original motor is close to the rated current value in this state.
The main motor that replaces the stator winding is embedded with PT100 platinum thermal resistance temperature measuring element in the stator winding. When the compressor is close to the processing capacity, the coil temperature is (6 718) e, and the original motor stator winding is embedded with bimetal, which is directly set. Alarm value and trip value, temperature cannot be detected at any time.
The main motor of the refrigerant cycle compressor is a kind of special motor, which has certain special characteristics in the process of use, maintenance and repair. The main motor after repair has been running well since it was put into operation.
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