OSM transformers are step-down armored, rod, or toroidal transformers designed to power lighting, control, and automation circuits. They are designed for power from 0.063 to 4 kV ยท A. Depending on it, transformers differ in size, mounting method and special impregnation with moisture-proof insulating varnish. The primary winding is designed to operate at voltages from 220 to 660 V. The secondary can work from 12 to 260 V. It is possible to design with several secondary windings for different voltages. Thus, the scope of transformers is quite wide.
What are OSMs?
What OSM transformers are, you can understand from the name itself. In this case, O is single-phase. C - means dry, not using transformer oil. This is due to low power and has a positive effect on weight and size. To protect against moisture and oxidation, a special varnish is used. M means it is multi-purpose.
According to the type of protection against electric shock, they belong to class I, and the degree of protection corresponds to IP00, however, the customer can manufacture a transformer with protection on the IP20 contacts. It should be borne in mind that transformers are not designed for installation in explosive atmospheres.
Withstand vibration load with a frequency of 10 to 60 Hz. The maximum acceleration should not exceed 2g. Able to withstand a shock whose acceleration does not exceed 8g.
Note that in addition to the armored type design, there are also OSM T. transformers. In this case, T means that it is of the toroidal type. Roughly speaking, it has the shape of a donut. With the same power, such transformers are lighter and smaller in size.
Design
The transformer OSM 0.25, 1 or 4 kV ยท A can be armored, rod or toroidal type. The choice of one or another option depends on the manufacturer, its capabilities and equipment. The type used does not have a significant effect on performance or reliability.
Cores for all options are made of electrical steel. In rod and toroidal type transformers, the winding encloses a core. But in the armored, on the contrary, the core contains a winding.
Coils have a frame structure. The material used is copper. The wire is enclosed in heat-resistant insulation.
On the upper part of the transformer, the beginning of the secondary and primary windings is indicated. The first corresponds to the designation "O", and the second to "U".
Installation Features
The transformer is intended for installation in equipment in which all protective equipment: from electric shock, water and overload, is carried out by the equipment itself. The windings are impregnated with moisture insulating varnish, carried out in a vacuum chamber. It is not recommended to install transformers in conditions involving the presence of vapors containing alkali and acids that can damage the materials of which the components of the device are made.
Each block clamp is designed to connect no more than two aluminum or copper wires. Their maximum cross-section should not exceed 2.5 mm. The case of the device must be grounded. The terminal of the secondary winding is also grounded if it is used for lighting. For safe operation, the insulation resistance should not be less than 0.5 Mฮฉ.
Transformers from 1.6 kV ยท A are designed for installation only on a horizontal surface. Models with a power of 1 kV ยท A and below can be installed on both horizontal and vertical surfaces.
Types of climatic modification
OSM transformers can be made in the following options:
- U3 - the first letter in this case means a temperate climate in which the transformer can operate. 3 is a category of placement, namely in enclosed spaces with natural ventilation.
- T3 - designed to work in a tropical climate, both with dry air and with high humidity. The placement category is the same as in the previous version.
- UHL3 - stands for temperate or cold climate.
Thus, all options are provided only for operation in enclosed spaces. In the open air or under a canopy work is not provided. They differ among themselves only in a protective coating from the external environment, but the characteristics of the OSM transformers and the dimensions are the same.
Deciphering Indices
Often you can see various indices for OSM transformers: 0.4, U3, 380, and so on. We will analyze in more detail what they mean, for example, OSM1-0.5-U3-380 / 5-36-220 / 12 TU:
- The number 1 at the very beginning indicates that the transformer is the first model.
- 0.5 - rated power. It must be borne in mind that if the transformer is three-winding, the power will be indicated by the total for two windings.
- U3 is the climatic conditions of work.
- 380 for this case shows the voltage on the primary winding.
- 5-36-220 are the voltages on the branches of the secondary winding. In this case, there are three.
- 12 - voltage of the third winding.
- TU - these are technical specifications.
Transportation and storage
During transportation, it is necessary to exclude any possibility of mechanical damage to transformers. Boxes must be securely fixed in the manner prescribed by the appropriate freight transport. Also for storage and transportation, it is important to prevent the likelihood of moisture or dew on the surface. Store at a relative humidity of not more than 80 percent. The presence of acid or alkaline vapors that can damage the materials of which the transformer is made, its impregnation or insulation, or cause the appearance of oxide, is unacceptable.