IEC 62590-2019 pdf free.Railway applications- Fixed installations- Electronic power converters for substations.
Semiconductor valves can be turned off either by commutation implying that the current of thevalve is transferred to another valve or by quenching if the current of the valve falls to zero.
Valves used in traction supply power converters can be divided into the following categories:a) non-controllable valve with a conductive forward and a blocking reverse characteristic(diode);
b) valve with a controllable forward and a blocking reverse characteristic (e.g.reverse blocking thyristor);
c) valve with a controllable forward and a conductive reverse characteristic (e.g. reverse conducting thyristor);
d) valve with a controllable forward and / or reverse characteristic which can be turned on and/or off via a signal applied to the gate (e.g. gate turn-off thyristor,insulated gate bipolartransistor);
e) valve with controllable forward and reverse characteristic (e.g. bi-directional thyristors).
At the transition current value, the voltage/current characteristic bends as shown in Figure 2.The transition current can be obtained, for example in case of interphase transformerconnection, because the direct current decreases below the critical value where the interphasetransformer becomes ineffective.
For both cases,direct cooling or indirect cooling, if the circulation is alternatively natural orforced, two groups of symbols, separated by a stroke, shall indicate both possible methods ofcirculation as used, the first group corresponding with the lower heat flow or the lower ambientair temperature.
Therefore, the complete code shall include:
a) for direct cooling: two groups of letters separated by a stroke.
EXAMPLE1 AN/AF: converter with natural direct air cooling and possibilities for forced direct air cooling;
b) for indirect cooling: two groups of letter symbols separated by a stroke.
EXAMPLE 2 OFAN/OFAF: converter with forced circulated oil as heat transfer agent and natural air as cooling medium with possibilities forforced air as cooling medium.
6.2Environmental conditions
6.2.1 Ambient air circulation
Equipment installed in a room shall be connected to the (unlimited) supply of cooling mediumor if the cooling air is taken from the ambient in the room, provision shall be made to extractthe heat from the room,which then can be considered as an intermediate heat-exchangerbetween the equipment and the outside air.
For converters mounted in an enclosure,the ambient for the converters (internal air of thecubicle or cabinet) is to be considered as a heat transfer agent and not as a cooling medium.There is some reflection from the cabinet walls,which should be taken into account.Cubicle or cabinet mounted assemblies shall comply with the overload conditions at maximum temperatureof the outside air.IEC 62590 pdf download.