Articles: Cases/PSU

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The cross-load characteristics are rather stable, but the +5V and +12V voltages are set too high, by 3-4%.

The oscillogram of high-frequency pulsations (one division of the horizontal axis means 10 microseconds) shows that the PSU barely but meets the requirements of the standard: the voltage ripple of the +5V rail is 50 millivolts, which is exactly the maximum allowable value.

Alas, when we switch into slower scanning, 2 milliseconds per division, we can see low-frequency pulsations on the +12V rail. The combined voltage ripple is thus over 150 millivolts (three divisions of the vertical axis), the allowable maximum being 120 millivolts. This oscillogram was recorded at full load. When the load is lower, the voltage ripple is lower, too.

The PSU employs Top Motor DF128025BU and Tagan S0801512HG fans (the latter one is actually manufactured by Globe Fan). The first fan is 80x80x25mm large and is classified as a high-speed model whereas the second one has a modest size of 80x80x15mm. However, there is only one fan speed curve on the PSU label, showing that the fan speed (I wonder what fan of the two it is?) varies from 1465rpm to 2690rpm, depending on current load.

The real situation is not that bright, though. Quite expectedly, the manufacturer showed the speed of the slower fan (S0801512HG) on the label and, presumably, measured it under an ambient temperature of 18°C because our graph, recorded at a room temperature of 24°C, has the same shape but is shifted upwards by 300-400rpm.

This is not the worst thing, though. The second fan (DF128025BU) indeed proved to be a high-speed one. Having started from 2200rpm, it reached 4200rpm at a load of 1000W. With this fan the diagram doesn’t look at all as pretty as the one on the PSU label.

And I even wonder if the low-speed fan is needed at all here. The push-pull design works well when both fans have identical, or at least similar, parameters. Here, we’ve got a powerful high-performance fan coupled with a rather slow and thin one (15mm instead of 25mm, and the thinner blades create lower static pressure). Moreover, we can consider the example of the above-described SilverStone Olympia OP1000 to see that its fan, with parameters similar to the DF128025BU, could cool the PSU easily all alone. So, I’ve got an impression that the second, low-speed fan of the Tagan TG1100-U96 PSU is mere decoration.

The Tagan TG1100-U96 can’t be called quiet, of course. It’s got its name of TurboJet for a reason. Although the more powerful fan is hidden deep in the system case, not every system case is going to muffle its noise which becomes very high at high loads on the PSU.

Well, noise is not the worst thing here, I think. After all, the competing models with an 80mm fan aren’t quiet, either. The bad thing is that the manufacturer attempts to mislead the customer by not mentioning the PSU’s having a second fan, which is powerful and noisy.

The efficiency of this PSU is quite typical for a 1000W model, a little less than 85% at the maximum. However, it degenerates quickly at loads below 200W, down to 50% at a load of 50W.

I can’t say I’m pleased with the Tagan TurboJet TG1100-U96. And my gripes are not actually about the PSU’s technical characteristics, but about how they are interpreted by the manufacturer. First, the pretty useless and cumbersome screening of the cables is advertised as a means to reduce noise and pulsations (but the PSU couldn’t fit into the requirements of the standard in terms of output pulsations; moreover, it is the single model among those included into this roundup that has a noticeable low-frequency voltage ripple on its output). Second, the PSU label shows a fan speed graph that is very misleading. It shows the speed of the slower of the two fans installed in the PSU. And talking about its parameters, the TG1100-U96 is at best equal to its opponents but is never better than them.

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