Articles: Cases/PSU

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I had to test the senior model under a load that was somewhat below its maximum because our testbed could only support PSUs with an output power of 1350W out of which 1100W could be taken from the +12V rail.

The PSUs worked together with an APC SmartUPS SC 620 at loads up to 375W (from the mains) and 340W (from the batteries). At higher loads the UPS would shut down some 5 seconds after switching to the batteries.

Alas, the output voltage ripple on the +3.3V rail exceeds the permissible limits. This voltage isn’t quite right in many high-wattage PSUs as you may have noticed. The +5V rail doesn’t meet the requirements as well if you note the individual spikes whose peaks are above the required 50 millivolts.

It’s almost the same with the 1500W model: the pulsation on the +3.3V rail violates the permissible limits while the pulsation on the +5V rail is as about as high as the limit.

But like with the above-discussed FSP Epsilon, the W0171RE specification at Thermaltake’s website says that the maximum allowable output voltage ripple is 240 millivolts for the 12V rail and 100 millivolts for the other rails, which is two times higher than the limits proposed in ATX12V Power Supply Design Guide. For the W0133RE model the maximum allowable limits comply with the standard. I don’t know if it is just a mistake or a deliberate attempt to “legalize” a power supply that does not comply with the industry standard.

Besides, there is low-frequency ripple, too. It is within the allowable limits, but I still regard the very existence of such pulsation as a drawback, even though not a crucial one.

It is the stability of the output voltages that is really a drawback of these PSUs. The +3.3V voltage sags heavily under load, not only when the +3.3V rail but also when the +12V rail, located in the same sub-PSU, is loaded. As a result, the maximum output power you can get from the PSU without exceeding the allowable 5% deflection is only some 950W. When the combined load on the +5V and +3.3V rails is 60W, the total output power of the PSU is only 600W.

It’s somewhat better with the senior model: the +3.3V voltage is still sagging, but the 5% border of the diagram has shifted to the right, the PSU providing over 1000W of power. On the other hand, there is no talking about 1500W here, and even these 1000W was obtained with voltages being on the verge of the allowable deflection from the nominal values.

The PSUs are cooled with 140x140x25mm Yate Loon D14BH-12 fans which have a rated speed of 2800rpm according to their manufacturer and 2300rpm according to Thermaltake.

The junior PSU model kept the fan speed constant until a load of 750W. However, that constant speed was not very low: the large 14cm fan was perfectly audible at 1300rpm.

The senior PSU model had a somewhat lower initial speed of the fan but started to increase it sooner: at a load of 600W. So, both PSUs are average in terms of noisiness and can stand a comparison with other high-wattage PSUs in this respect but they won’t suit people who want to have a silent PC.

Both PSUs have a normal efficiency, 80-83%. The power factor is over 0.95 as is typical of PSUs with active power factor correction.

The question I am always asking when testing such PSUs – what PC configuration might require that much power? – is complimented with the cross-load diagrams when it comes to the two PSUs from Thermaltake. Alas, none of them could provide its full output power in my tests just because the +3.3V voltage exceeded the permissible 5% deflection from the nominal value long before that moment. As a result, we cannot say too many really good things about the Toughpower W0133RE and W0177RE: high price, not very good stability of the output voltages, obviously overstated specified output power, rather noisy fans…

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