Transformer rated values
Transformers are equipped with a plaque containing all the information needed for transformer selection under normal circumstances.
- Upri = nominal primary voltage, or the supply main voltage (V)
- Usec = nominal secondary voltage with nominal secondary current (V)
- Sn = transformer’s nominal apparent power on the secondary side (VA) or
- Isec = nominal secondary current (A)
- f = transformer’s nominal frequency (Hz)
In atypical situations, the following are also required
- protection class if other than class I (I = protective grounding, II = double insulation, III = extra-low voltage)
- casing class if other than IP00
- ta = ambient temperature if other than 25ºC
- intermittent usage percentage if other than 100 %
- transformer symbol according to standard
When a transformer is ordered, its mechanical requirements as well as possible short-circuit protection and overload protection must be determined.
Transformer Symbols
Enclosures for electrical equipment, ie IP classes
An IP class is a two-digit code that describes the ability of an electrical device’s outer shell to protect;
- environmental hazards inside the device (voltage, device moving parts)
- the sensitive parts of the device from dirt, dust or water that penetrates the environment
The IP class is a standardized classification for the safety of electrical equipment and applies to all electrical appliances such as transformers, electric motors, electrical cabinets and lighting fixtures.
First ID number |
Contact properties and barrier properties (occupational safety) of protection class |
0 | Open, unprotected structure |
1 | Entry of at least 50 mm in size blocked, including inadvertent access to body parts such as hands |
2 | Finger guarding, blocked at least 12 mm in length, blocking up to 80 mm in diameter and up to 12 mm in diameter for dangerous parts is prevented |
3 | Entry of at least 2.5 mm in size such as spikes, screws and machining waste is prevented |
4 | Entry of at least 1 mm in size such as threads, ribbons, and machining waste is prevented |
5 | The entry of dust harmful to the operation of the device is prevented |
6 | Dust penetration is prevented |
Second identification number |
Protection from water |
0 | Open, unprotected structure |
1 | Dripping water in vertical droplets does not hurt |
2 | Dripping water in vertical droplets does not cause harm, even though the casing tilts up to 15º in an arbitrary direction from the normal position |
3 | Water at an angle of up to 60 ° does not cause any damage |
4 | Water splashing from all directions does not cause any harm |
5 | A water wave or a powerful jet of water directed from all directions by the nozzle does not cause any harm |
6 | A powerful jet of water directed from all directions by the nozzle does not cause any harm |
7 | Water is not penetrated into the enclosure by water in the short term |
8 | The device can be kept immersed in water according to the manufacturer’s instructions, so that there is no harmful intrusion into the enclosure |