Antec Phantom 500 (500W)
The Phantom 500 comes from a rather rare variety of power supplies. The manufacturers usually call them semi-fanless, meaning that the fan of such a PSU starts to work only at a big load (to be exact, when the temperature inside the PSU exceeds a certain threshold). The Phantom 500 grew out of the fanless Phantom 300. The fan that works only under high loads has helped to raise the wattage of the model.
The Phantom is manufactured by CWT that supplies a lot of PSU models for Antec (for example, the widely known TruePower series).
Many manufacturers of semi-fanless power supplies usually take a standard design of a fan-equipped PSU and enlarge its heatsinks (or even put them outside with the help of heat pipes), but the Phantom 500 shows traces of much deeper developmental work, obviously inherited from its fanless predecessor. You can see a lot of heatsinks here, only two of which belong to the transistors and diode packs (these are the components that have heatsinks in any power supply). The others cool the chokes.
When the PSU is closed, the heatsinks press down through heat-conducting pads to the bottom panel of the PSU which is a big ribbed aluminum heatsink in itself. This means that some air cooling is desirable. An additional low-speed fan on the rear panel of your system case, creating airflow along the PSU’s bottom panel, will do much good to the PSU’s thermal conditions.
The top panel of the Phantom 500 is designed like a heatsink, too, but only for the sake of aesthetics. None of the hot components in the PSU has thermal contact with it.
It is the transistors and diode packs that are traditionally considered the hottest components in a power supply, yet it is not exactly so. The chokes heat up a lot, too, due to the high current passing through them. In an ordinary PSU they are effectively cooled by the airflow, but in a fanless model those chokes have to be made with some reserve or have to be cooled somehow. The photograph above shows the two chokes of the output regulators on magnetic amplifiers (the PSU features independent voltage regulation) that are pressed through a soft heat-conducting pad to the heatsink with diode packs.