Types of duty

 Types of operation.
There are the following types of operation:

1. Continuous operation - (S1)  Operation with a constant load and for an unlimited period of time or at least until a determined temperature increase is achieved. Figure 1 below shows operating period and temperature rise verses time for continuous operation.


 
Fig.1 Continuous operation (S1)
Tmax – temperature determined for continuous operation.
Descriptions: Moc – Power, Straty elektryczne – Electric losses, Temperatura - Temperature
 

2. Short-time operation - (S2) Operation for a determined period of time, starting from cold state, with breaks in operation long enough to cool the transformer down to a temperature close to ambient. Operating time (tp ) is given in minutes (e.g. S2-15 min.). Figure 2 below shows operating duty cycle and temperature rise for short-time operation.


Fig. 2 Short-time operation (S2)
Tmax – highest temperature at short-time operation, tp – time of short-time operation.
Descriptions: Moc – Power, Straty elektryczne – Electric losses, Temperatura - Temperature
 

3. Discontinuous operation - (S3) Consecutive periods of operation and break with a predetermined duty cycle. Discontinuous operation may be designated for example as S3-20%, where the percentage value indicates the ratio of operation time (tp) to the cycle period (t0), where t0 =tp+ts.

Figure 3 below shows operating duty cycle and temperature rise for discontinuous operation.


Fig. 3 Discontinuous operation (S3)
Tmax – highest temperature at discontinuous operation, tp – time of operation, t0 –period duration,
ts – standstill duration.
Description: Moc – Power, Straty elektryczne – Electric losses, Temperatura - Temperature

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