Zalman ZM1000-HP: Quiet KiloWatt PSU

Power
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TESTING

For a fuller understanding of ATX power supplies, please read the reference article Power Supply Fundamentals & Recommended Units. Those who seek source materials can find Intel's various PSU design guides at Form Factors.

For a complete rundown of testing equipment and procedures, please refer to SPCR's PSU Test Platform V4.1. The testing system is a close simulation of a moderate airflow mid-tower PC optimized for low noise.

In the test rig, the ambient temperature of the PSU varies proportionately with its output load, which is exactly the way it is in a real PC environment. But there is the added benefit of a high power load tester which allows incremental load testing all the way to full power for any non-industrial PC power supply. Both fan noise and voltage are measured at various standard loads. It is, in general, a very demanding test, as the operating ambient temperature of the PSU often reaches >40°C at full power. This is impossible to achieve with an open test bench setup.

The 120mm fan responsible for "case airflow" is deliberately run at a steady low level (~6-7V) when the system is run at "low" loads. When the test loads become greater, the 120mm fan is turned up to a higher speed, but one that doesn't affect the noise level of the overall system. Anyone who is running a system that draws 400W or more would definitely want more than 20CFM of airflow through their case, and at this point, the noise level of the exhaust fan is typically not the greatest concern.

Great effort has been made to devise as realistic an operating environment for the PSU as possible, but the thermal and noise results obtained here still cannot be considered absolute. There are too many variables in PCs and too many possible combinations of components for any single test environment to provide infallible results. And there is always the bugaboo of sample variance. These results are akin to a resume, a few detailed photographs, and some short sound bites of someone you've never met. You'll probably get a pretty good overall representation, but it is not quite the same as an extended meeting in person.

REAL SYSTEM POWER NEEDS: While we test the PSU to full output in order to verify the manufacturer's claims, real desktop PCs simply do not require anywhere near this level of power. The most pertinent range of DC output power is between about 40W and 300W, because it is the power range where most systems will be working most of the time. To illustrate this point, we conducted system tests to measure the power draw of several actual systems under idle and worst-case conditions. Our most power-hungry overclocked 130W TDP processor rig with an ATI Radeon X1950XTX-512 graphics card drew ~256W DC peak from the power supply under full load — well within the capabilities of any modern power supply. Please follow the link provided above to see the details. It is true that very elaborate systems with the most power hungry dual video cards today might draw as much as another 150~200W, but the total should remain under 500W in extrapolations of our real world measurements.

SPCR's high fidelity sound recording system was used to create MP3 sound files of this PSU. As with the setup for recording fans, the position of the mic was 3" from the exhaust vent at a 45° angle, outside the airflow turbulence area. The photo below shows the setup (a different PSU is being recorded). All other noise sources in the room were turned off while making the sound recordings.

INTERPRETING TEMPERATURE DATA

It important to keep in mind that fan speed varies with temperature, not output load. A power supply generates more heat as output increases, but is not the only the only factor that affects fan speed. Ambient temperature and case airflow have almost as much effect. Our test rig represents a challenging thermal situation for a power supply: A large portion of the heat generated inside the case must be exhausted through the power supply, which causes a corresponding increase in fan speed.

When examining thermal data, the most important indicator of cooling efficiency is the difference between intake and exhaust. Because the heat generated in the PSU loader by the output of the PSU is always the same for a given power level, the intake temperature should be roughly the same between different tests. The only external variable is the ambient room temperature. The temperature of the exhaust air from the PSU is affected by several factors:

  • Intake temperature (determined by ambient temperature and power output level)
  • Efficiency of the PSU (how much heat it generates while producing the required output)
  • The effectiveness of the PSU's cooling system, which is comprised of:
    • Overall mechanical and airflow design
    • Size, shape and overall surface area of heatsinks
    • Fan(s) and fan speed control circuit

The thermal rise in the power supply is really the only indicator we have about all of the above. This is why the intake temperature is important: It represents the ambient temperature around the power supply itself. Subtracting the intake temperature from the exhaust temperature gives a reasonable gauge of the effectiveness of the power supply's cooling system. This is the only temperature number that is comparable between different reviews, as it is unaffected by the ambient temperature.

TEST RESULTS

Note that the test data shows just two 12V lines. Three separate loads were used: One for the main ATX and drive power output cables, one for the AUX12V connectors, and one for the PCIe 16X power connectors. The latter loads were combined and listed under 12V2 for convenience. Otherwise, the table (and the page) get too wide to read with any ease.

The ambient temperature was 20°, and the noise level was 19 dBA.

OUTPUT, VOLTAGE REGULATION & EFFICIENCY: Zalman ZM1000-HP
DC Output Voltage (V) + Current (A)
Total DC Output
AC Input
Calculated Efficiency
+12V1
+12V2
+5V
+3.3V
-12V
+5VSB
12.22
0.96
12.22
1.73
5.08
0.97
3.34
0.94
0
0.1
41
59
70.4%
12.22
1.89
12.22
1.73
5.07
1.95
3.34
2.63
0.1
0.2
65
85
76.6%
12.22
2.84
12.22
3.27
5.07
0.91
3.34
2.63
0.1
0.3
91
152
80.3%
12.21
4.71
12.22
4.95
5.06
3.70
3.31
3.62
0.1
0.5
152
183
83.3%
12.20
6.57
12.18
6.46
5.04
4.46
3.34
4.43
0.2
0.7
202
235
86.0%
12.19
7.72
12.17
8.06
5.04
6.35
3.33
5.22
0.2
0.9
249
288
86.3%
12.19
9.59
12.14
9.78
5.02
8.02
3.29
7.36
0.2
1.1
308
357
86.2%
12.19
7.74
12.15
17.38
5.01
10.58
3.27
9.01
0.3
1.4
399
461
86.5%
12.16
9.56
12.13
23.58
5.00
10.49
3.25
9.65
0.4
1.7
500
584
85.6%
12.09
9.56
12.14
27.57
4.98
16.10
3.21
15.78
0.5
2.1
598
712
84.0%
12.09
15.06
12.04
36.95
4.92
19.11
3.15
18.17
0.6
2.8
799
989
80.8%
12.02
21.07
12.02
45.71
4.88
22.00
3.12
20.78
0.8
3.1
1000
1276
78.4%
Crossload Test
12.00
21.01
12.01
45.66
4.95
0.98
3.29
0.9
0.1
0.1
812
1008
80.8%
+12V Ripple (peak-to-peak): 15mV @ 200W ~ 109mV @ 651W (max)
+5V Ripple (peak-to-peak): 12mV @ 200W ~ 47mV @ 600W (max)
+3.3V Ripple (peak-to-peak): 23mV @ 40W ~ 83mV @ 800W (max)
NOTE: The current and voltage for -12V and +5VSB lines is not measured but based on switch settings of the DBS-2100 PS Loader. It is a tiny portion of the total, and potential errors arising from inaccuracies on these lines is <1W.

OTHER DATA SUMMARY: Zalman ZM1000-HP
DC Output (W)
41
65
91
152
202
249
308
399
500
598
799
1000
Intake (°C)
20
22
26
28
29
29
32
36
40
41
42
45
Exhaust (°C)
23
25
30
33
36
39
41
50
55
60
66
70
Temp Rise (°C)
3
3
4
5
7
10
9
14
15
19
24
25
Fan Voltage (V)
4.6
4.6
4.6
4.6
4.6
4.6
4.6
4.6
7.0
10.7
12.1
12.1
SPL (dBA@1m)
20
20
20
20
20
20
20
20
26
37
40
40
Power Factor
0.63
0.81
0.96
0.97
0.99
0.99
1.00
1.00
0.99
1.00
1.00
1.00
AC Power in Standby: 0.7W / 0.05 PF
AC Power in Standby, No Noise switch On: 1.7W / 0.15 PF
AC Power with No Load, PSU power On: 9.3W / 0.24 PF
NOTE: The ambient room temperature during testing can vary a few degrees from review to review. Please take this into account when comparing PSU test data.

ANALYSIS

1. EFFICIENCY This is a measure of AC-to-DC conversion efficiency. The ATX12V Power Supply Design Guide recommends 80% efficiency or better at all output power loads. 80% efficiency means that to deliver 80W DC output, a PSU draws 100W AC input, and 20W is lost as heat within the PSU. Higher efficiency is preferred for reduced energy consumption and cooler operation. The latter allows reduced cooling airflow, which translates to lower noise.

Even at the low output load of just 41W, the efficiency of the ZM1000-HP was a reasonably high 70.4%. This is as good as the vast majority of PSUs tested, even those with much lower top rated power (which generally have better efficiency at such low loads). >80% efficiency was seen at 90W output. A broad peak exceeding 86% was maintained between 200~500W. It edges the Enermax Modu82+ 625W for the title of most efficient PSU we've reviewed. That >80% efficiency was not maintained to 1000W output in this 80 Plus approved PSU is no surprise. 80 PLUS testing is performed at room temperature, unlike the thermal chamber of SPCR's test setup. At high temperature, it's normal for efficiency to drop. The ZM1000-HP had been under continuous escalating load for close to four hours when the final full load measurements were taken. That was a torture test.

2. VOLTAGE REGULATION refers to how stable the output voltages are under various load conditions. The ATX12V Power Supply Design Guide calls for the +12, +5V and +3.3V lines to be maintain within ±5%. At virtually all loads, all the voltages were just about dead on, especially on the all-important 12V line. The worst voltage drop was at full load on the 3.3V line; the drop amounted to 0.18V or just over -5%.

3. AC RIPPLE refers to unwanted "noise" artifacts in the DC output of a switching power supply. It's usually very high in frequency (in the order of kilohertz or megahertz). The peak-to-peak value is measured. The ATX12V Guide allows up to 120mV (peak-to-peak) of AC ripple on the +12V line and 50mV on the +5V and +3.3V lines.

Ripple started low but climbed steadily as output was increased. Both the 12V and 5V ripple reached close to the maximum allowed at around 600W load. The ripple for the 3.3V line was clearly exceeded at the 800W combined output level.

How important is this? It's difficult to say. We've never seen a system draw more than 400W from the AC line, never mind demand 800W in DC. It's not likely that the higher than allowed ripple on the 3.3V line at 800W would result in misbehavior in a real system; it's hard to imagine how a system could be configured (and then run) to pull that much power.

4. POWER FACTOR is ideal when it measures 1.0. In the most practical sense, PF is a measure of how "difficult" it is for the electric utility to deliver the AC power into your power supply. High PF reduces the AC current draw, which reduces stress on the electric wiring in your home (and elsewhere up the line). It also means you can do with a smaller, cheaper UPS backup; they are priced according to their VA (volt-ampere) rating. PF on this model was excellent thanks to the active power factor correction circuit, staying at or very close to the theoretical maximum of 1.0.

5. LOW LOAD TESTING revealed no problems starting at very low loads. Our sample had no issue starting up with no load at all.

6. LOW AND 240 VAC PERFORMANCE

The power supply was set to 600W load with 120VAC through the hefty variac in the lab. The variac was then dialed 10V lower every 10 minutes. This is to check the stability of the PSU under brownout conditions where the AC line voltage drops from the 110~120V norm. The ZM1000-HP is rated for operation 115VAC ~ 240VAC ±10%. Most power supplies achieve higher efficiency with higher AC input voltage. SPCR's lab is equipped with a 240VAC line, used to check power supply efficiency for the benefit of those who live in 240VAC mains regions.

Low VAC Test: Zalman ZM1000-HP @ 600W Output
VAC
AC Power
Efficiency
242V
688W
87.0%
120V
712W
84.0%
110V
719W
83.2%
100V
727W
82.3%

The low voltage test was passed within spec. Neither voltage regulation nor ripple changed measurably during the test, and efficiency dropped only marginally. Efficiency improved with 240VAC input, around 3 percentage points at 600W. In its peak efficiency range of 200W~500W, the unit will reach close to 90% efficiency with 240VAC input.



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