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Enermax Platimax 850w Power Supply Review (EPM850EWT)

Additional technical assistance: Peter McFarland and Jeremy Price.

Correctly testing power supplies is a complex procedure and KitGuru have configured a test bench which can deliver up to a 2,000 watt DC load. Due to public requests we have changed our temperature settings recently – previously we rated with ambient temperatures at 25C, we have increased ambient temperatures by 10c (to 35c) in our environment to greater reflect warmer internal chassis conditions.

We use combinations of the following hardware:
• SunMoon SM-268
• CSI3710A Programmable DC load (+3.3V and +5V outputs)
• CSI3711A Programmable DC load (+12V1, +12V2, +12V3, and +12V4)
• Extech Power Analyzer
• Extech MultiMaster MM570 digital multimeter
• Extech digital sound level meter
• Digital oscilloscope (20M S/s with 12 Bit ADC)
• Variable Autotransformer, 1.4 KVA

12V output is combined for our testing.

DC Output Load Regulation

Combined

DC Load

+3.3V
+5V
+12V
+5VSB
-12V
A
V
A
V
A
V
A
V
A V
100W
1.52
3.37
1.75
5.07
6.63
12.13
0.50
5.04
0.20 -12.17
225W
3.78
3.35
3.82
5.06
15.53
12.11
1.00
5.03
0.20 -12.13
450W
7.52
3.33
8.35
5.05
30.77
12.07
1.50
5.04
0.30 -12.11
675W 11.32 3.32 12.33 5.03 47.54 12.04 2.00 5.00 0.50 -12.07
850W
1.45
3.30
1.17
5.01
63.45
12.00
0.50
4.99
0.20 -12.04

The Enermax Platimax 850W produces strong load regulation across all output. They all achieved between +/-3% of the nominal voltage instead of the recommended +/-5%.

Enermax Platimax 850w Maximum Load
972W

We managed to get the PSU to achieve 972W before it would shut down, delivering around 122W more than the rated specifications.

Next we want to try Cross Loading. This basically means loads which are not balanced. If a PC for instance needs 500W on the +12V outputs but something like 30W via the combined 3.3V and +5V outputs then the voltage regulation can fluctuate badly.

Cross Load Testing +3.3V +5V +12V -12V +5VSB
A V A V A V A V A V
760W 1.0 3.38 1.0 5.04 60.0 11.98 0.2 -12.05 0.50 5.00
165W 15.0 3.29 18.0 5.01 2.0 12.06 0.2 -12.01 0.50 5.00

These are fantastic results under intensive load changes, with all output holding well. The +12V output fluctuates by only 0.08 when loaded.

We then used an oscilloscope to measure AC ripple and noise present on the DC outputs. We set the oscilloscope time base to check for AC ripple at both high and low ends of the spectrum.

ATX12V V2.2 specification for DC output ripple and noise is defined in the ATX 12V power supply design guide.

ATX12V Ver 2.2 Noise/Ripple Tolerance
Output
Ripple (mV p-p)
+3.3V
50
+5V
50
+12V1
120
+12V2
120
-12V
120
+5VSB
50

Obviously when measuring AC noise and ripple on the DC outputs the cleaner (less recorded) means we have a better end result. We measured this AC signal amplitude to see how closely the unit complied with the ATX standard.

AC Ripple (mV p-p)
DC Load +3.3V +5V +12V 5VSB
100W 10 5 15 10
225W 10 10 15 10
450W 10 10 20 15
675W 15 10 25 15
850W 20 10 35 20

Ripple results are extremely impressive across all output, with the +12V rail peaking at 35 mV @ full load. All fall well within the recommended specifications.

Efficiency (%)
100W
90.66
225W
91.45
450W
93.75
675W
91.73
850W 90.68

The power supply, as expected, is extremely efficient, peaking at 93.75% around 50%. It drops down to just below 91 percent at full load, very strong results across the range of output.

We take the issue of noise very seriously at KitGuru and this is why we have built a special home brew system as a reference point when we test noise levels of various components. Why do this? Well this means we can eliminate secondary noise pollution in the test room and concentrate on components we are testing. It also brings us slightly closer to industry standards, such as DIN 45635.

Today to test the power supply we have taken it into our acoustics room environment and have set our Digital Sound Level Noise Decibel Meter Style 2 one meter away from the unit. We have no other fans running so we can effectively measure just the noise from the unit itself.

As this can be a little confusing for people, here are various dBa ratings in with real world situations to help describe the various levels.

KitGuru noise guide
10dBA – Normal Breathing/Rustling Leaves
20-25dBA – Whisper
30dBA – High Quality Computer fan
40dBA – A Bubbling Brook, or a Refridgerator
50dBA – Normal Conversation
60dBA – Laughter
70dBA – Vacuum Cleaner or Hairdryer
80dBA – City Traffic or a Garbage Disposal
90dBA – Motorcycle or Lawnmower
100dBA – MP3 Player at maximum output
110dBA – Orchestra
120dBA – Front row rock concert/Jet Engine
130dBA – Threshold of Pain
140dBA – Military Jet takeoff/Gunshot (close range)
160dBA – Instant Perforation of eardrum

Noise (dBA)
100W
29.0
225W
30.4
450W
31.2
675W
33.7
850W 34.3

We have plenty of experience with the Enermax Twister based fans in the past and this configuration is just as impressive. Generally the power supply is inaudible, with the fan only working harder in the last 20% of power output. Even then it would be drowned out by a couple of chassis fans.

Temperature (c)
Intake
Exhaust
100W
35
38
225W
37
42
450W
41
48
675W
43
51
850W
44
53

The large 13.9cm Twister fan maintains a high level of airflow, maintaining good ambient temperatures. At full load the temperature rises to a 9c above ambient intake threshold.

Maximum load
Efficiency
972W
88.2%

Even at 972W, the unit exhibits very strong efficiency levels, measuring 88.2%. Be aware this isn’t a realistic long term situation 24/7 but it shows that the power supply has a lot of headroom for quick load situations.

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