Evolution of technical standards for oil-immersed power transformers

1, JB500-1964 transformer public standard

The JB500-1964 transformer process standard was the ministerial standard of the former Ministry of Machinery Industry in 1964. Its performance data is comparable to the original Soviet national standard IOCT401-1941. This series of transformers has high loss and low efficiency. It is called a high-energy-consumption transformer and has been eliminated and is no longer used. In order to understand the development history of transformer technology performance, the technical performance of the partial capacity of SJL6 and 1OkV series transformers designed according to this standard is listed in Table 2-1 for reference.

2. CB1094-1971, CB1094-1979, JB1300-1304-1973 standard

GB1094-1971 transformer process standard is the national standard revised in 1971. Later it was changed to GBID94-1979, the technical performance of the product complies with the ministerial standard JB1300-1304-1973 (three-phase oil-immersed power transformer drop parameters and technical requirements). The technical performance of this series of transformers is much improved compared to JB500-1964. It is called medium loss transformer and was eliminated in the early 1980s.

3. GB1094*1~5-1985 and GB6451*1~5-1986 national standards

Since 1979, China's transformer industry has identified new targets for small and medium-sized transformers, and has begun to design energy-saving and low-voltage transformers. The joint design was completed in 1981, and the prototype was made in 1982. So we have established 10~35kV national unified design SL7 and SLZ, low loss transformers, as a national promotion project. lOkV level

The no-load loss of the transformer is reduced by about 40% compared to the high-energy SJL series transformers manufactured according to JB500-1964. At the same time, the load loss is also reduced by more than 10%, called a low-loss transformer, into an energy-saving transformer.

The main measures for reducing the loss of iron core material used is cold rolled grain oriented silicon steel sheet, steel sheet good performance, loss of small units. And improve the iron core production process, that is, the use of 45-degree oblique joints, as far as possible to make the magnetic flux along the silicon steel sheet rolling direction 45 degrees through the core joint, thereby greatly reducing the no-load current. At the same time, the core is not punched, and the structure of the tie is used to improve the utilization of the core. Moreover, the silicon steel sheet is not painted, and the insulation film of the silicon steel sheet itself is used to reduce the gap between the silicon steel sheets. When the silicon steel sheet is sheared, the burr is strictly avoided, and the joint of the core is smooth and tight, thereby achieving the goal of reducing the no-load loss and the no-load current. Since the utilization of the core is improved, the volume of the core is reduced, the coil is reduced, and the load loss is also reduced.

On the basis of the development of S7 low-loss transformer, China issued a new transformer process standard GB1094·1-5-1985 and a new oil-immersed transformer technical parameter GB6451·1~5-1986, which is the S7 transformer from 1985 to 1986. National standard. This standard has also been phased out.

A dumbwaiter is a small freight elevator or lift intended to carry objects rather than people. Dumbwaiters found within modern structures, including both commercial, public and private buildings, are often connected between multiple floors. When installed in restaurants, schools, kindergartens, hospitals, retirement homes or in private homes, the lifts generally terminate in a kitchen.

The term seems to have been popularized in the United States in the 1840s, after the model of earlier "dumbwaiters" now known as serving trays and lazy Susans. The mechanical dumbwaiter was invented by George W. Cannon, a New York City inventor. Cannon first filed for the patent of a brake system (US Patent no. 260776) that could be used for a dumbwaiter on January 6, 1883. Cannon later filed for the patent on the mechanical dumbwaiter (US Patent No. 361268) on February 17, 1887.Cannon reportedly generated a vast amount of royalties from the dumbwaiter patents until his death in 1897.

A simple dumbwaiter is a movable frame in a shaft, dropped by a rope on a pulley, guided by rails; most dumbwaiters have a shaft, cart, and capacity smaller than those of passenger elevators, usually 45 to 450 kg (100 to 1000 lbs.) Before electric motors were added in the 1920s, dumbwaiters were controlled manually by ropes on pulleys.

Early 20th-century codes sometimes required fireproof dumbwaiter walls and self-closing fireproof doors and mention features such as buttons to control movement between floors and locks on doors preventing them from opening unless the cart is stopped at that floor. Dumbwaiter Lifts in London were extremely popular in the houses of the rich and privileged. Maids would use them to deliver laundry to the laundry room from different rooms in the house. They negated the need to carry handfuls of dirty washing through the house, saving time and preventing injury.

A legal complaint about a Manhattan restaurant's dumbwaiter in 1915, which also mentions that food orders are shouted up and down the shaft, describes its operation and limitations as follows:

[There is] ... great play between the cart of the dumb-waiter and the guides on which it runs, with the result that the running of the cart is accompanied by a loud noise. The rope which operates the cart of the dumb-waiter runs in a wheel with a very shallow groove, so that the rope is liable to and does at times slip off. ... The cart has no shock absorbers at the top, so that when it strikes the top of the shaft or wheel there is a loud report. ... [T]he ropes of the dumb-waiter strike such wall at frequent intervals with a loud report. ... [T]he dumb-waiter is often negligently operated, by running it faster than necessary, and by letting it go down with a sudden fall.

More recent dumbwaiters can be more sophisticated, using electric motors, automatic control systems, and custom freight containers of other kinds of elevators. Recently constructed book lifts in libraries and mail or other freight transports in office towers may be larger than many dumbwaiters in public restaurants and private homes, supporting loads as heavy as 450 kg (990lbs)

Dumbwaiter Lifts

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