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Efficiency, Temperature & Noise
Efficiency
Our efficiency testing procedure is detailed here.
Using results from the previous page, we plotted a chart showing the ST1500-TI's efficiency at low loads, and loads from 10 to 110 percent of its maximum-rated capacity.
There is no doubt that this is an efficient platform. Under light loads, however, we would like to see slightly higher efficiency readings.
Efficiency At Low Loads
In the following tests, we measure the ST1500-TI's efficiency at loads significantly lower than 10 percent of its maximum capacity (the lowest load the 80 PLUS standard measures). The loads we dialed were 20, 40, 60, and 80W. This is important for representing when a PC is idle, with power-saving features turned on.
| Test # | 12V | 5V | 3.3V | 5VSB | DC/AC (Watts) | Efficiency | Fan Speed | PSU Noise | PF/AC Volts |
|---|---|---|---|---|---|---|---|---|---|
| 1 | 1.207A | 0.481A | 0.475A | 0.196A | 19.658 | 65.444% | 0 RPM | <6.0 dB(A) | 0.819 |
| 12.098V | 5.109V | 3.367V | 5.099V | 30.038 | 115.09V | ||||
| 2 | 2.442A | 0.967A | 0.980A | 0.391A | 39.762 | 74.821% | 0 RPM | <6.0 dB(A) | 0.900 |
| 12.096V | 5.106V | 3.363V | 5.091V | 53.143 | 115.09V | ||||
| 3 | 3.673A | 1.462A | 1.486A | 5.079A | 59.876 | 81.218% | 0 RPM | <6.0 dB(A) | 0.899 |
| 12.094V | 5.103V | 3.360V | 5.079V | 73.723 | 115.08V | ||||
| 4 | 4.896A | 1.963A | 1.966A | 0.785A | 79.791 | 84.082% | 0 RPM | <6.0 dB(A) | 0.941 |
| 12.092V | 5.100V | 3.356V | 5.070V | 94.897 | 115.09V |
With 20W load, the ST1500-TI cannot achieve a >70% efficiency score. But don't forget that 20W is just too low for a 1500W PSU, which uses a lot of large components in order to facilitate high power output. The energy lost on those components inevitably affects efficiency under light loads. On the bright side, the ST1500-TI's fan doesn't operate during those light load tests, even at an ambient temperature in excess of 36°C.
5VSB Efficiency
The ATX specification, along with CEC, ErP Lot 3 2014 and ErP Lot 6 2010/2013, states that 5VSB standby supply efficiency should be as high as possible, recommending 75 percent or higher with 550mA, 1A, and 1.5A of load. The PSU should also achieve higher than 75% efficiency at 5VSB under full load, or with 3A if its max current output on this rail is higher than 3A.
We take six measurements: one each at 100, 250, 550, 1000, and 1500mA, and one with the full load the 5VSB rail can handle.
| Test # | 5VSB | DC/AC (Watts) | Efficiency | PF/AC Volts |
|---|---|---|---|---|
| 1 | 0.101A | 0.505 | 68.428% | 0.037 |
| 4.981V | 0.738 | 115.10V | ||
| 2 | 0.252A | 1.252 | 74.836% | 0.083 |
| 4.975V | 1.673 | 115.09V | ||
| 3 | 0.542A | 2.690 | 77.566% | 0.164 |
| 4.963V | 3.468 | 115.09V | ||
| 4 | 1.002A | 4.954 | 80.776% | 0.262 |
| 4.944V | 6.133 | 115.09V | ||
| 5 | 1.502A | 7.394 | 81.639% | 0.341 |
| 4.924V | 9.057 | 115.09V | ||
| 6 | 3.001A | 14.582 | 79.061% | 0.473 |
| 4.859V | 18.444 | 115.09V |
With 115V input, the PSU's efficiency is satisfactory (though it'd be nice to see a >70% reading with 0.1A load). We should note that this rail is more efficient with 115V input than 230V, which is the opposite of what happens on the other rails under normal loads.
Power Consumption In Idle And Standby
In the table below, you'll find the power consumption and voltage values of all rails (except -12V) when the PSU is idle (powered on, but without any load on its rails), and the power consumption when the PSU is in standby mode (without any load, at 5VSB).
| Mode | 12V | 5V | 3.3V | 5VSB | Watts | PF/AC Volts |
|---|---|---|---|---|---|---|
| Idle | 12.103V | 5.113V | 3.369V | 5.112V | 0.281 | 0.015 |
| 115.1V | ||||||
| Standby | 0.112 | 0.006 | ||||
| 115.1V |
Since this is a high-capacity PSU, it is normal to measure over 0.1W vampire power. That's still lower than the ErP Lot 6 2013 limits.
Fan RPM, Delta Temperature, And Output Noise
Our mixed noise testing is described in detail here.
The first chart below illustrates the cooling fan's speed (in RPM), and the delta between input and output temperature. The results were obtained at 37°C (98.6°F) to 48°C (118.4°F) ambient temperature.
The next chart shows the cooling fan's speed (again, in RPM) and output noise. We measured acoustics from one meter away, inside a hemi-anechoic chamber. Background noise inside the chamber was below 6 dB(A) during testing (it's actually much lower, but our sound meter’s microphone hits its floor), and the results were obtained with the PSU operating at 37°C (98.6°F) to 48°C (118.4°F) ambient temperature.
The following graph illustrates the fan's output noise over the PSU's operating range. The same conditions of the above graph apply to our measurements, though the ambient temperature was between 30°C (86°F) to 32°C (89.6°F).
Under normal operating temperatures, the ST1500-TI's passive mode lasts until the load reaches ~210W. After that, and with up to 750W loads, the PSU's fan is within the 25-30 dB(A) range. We wouldn't call it annoying. The fan's noise increases to 30-35 dB(A) for a short time, then quickly rises to noise levels in excess of 40 dB(A) with 910W and higher loads.
Given this platform's high efficiency, we strongly believe that SilverStone could use a more relaxed fan profile, or at least implement a digital fan control circuit that would allow for a smoother transition between fan speeds. The lowest setting is still quite high, resulting in >25 dB(A). With the right circuit, the fan could get closer to 15-20 dB(A) at its slowest speed.
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