XigmaTek NRP-PC702 Power Supply Review

1. Introduction2. The Packaging/Bundle3. XigmaTek NRP-PC7024. XigmaTek NRP-PC702 (Inside)5. Testing Methodology and Results6. Closing Thoughts7. View All Pages

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
• SkyTronic DSL 2 Digital Sound Level Meter (6-130dBa)
• Digital oscilloscope (20M S/s with 12 Bit ADC)
• Variable Autotransformer, 1.4 KVA

We will combine both 12V rails into one for testing today.

DC Output Load Regulation
Combined DC Load	+3.3V		+5V		+12V		+5VSB		-12V
	A	V	A	V	A	V	A	V	A	V
174W	3.25	3.36	3.25	5.00	11.50	12.11	0.75	5.18	0.12	-12.09
352W	7.50	3.33	7.50	4.99	23.00	12.10	1.50	5.10	0.25	-12.10
525W	11.25	3.33	11.25	4.98	34.50	12.08	2.25	5.05	0.37	-12.10
700W	15.00	3.31	15.00	4.97	46.50	12.06	3.0	4.99	0.50	-12.11

The Xigmatek power supply is able to handle our load tests with relative ease even when delivering the maximum rated power output of 700W.

XigmaTek NRP-PC702	Maximum Load
	787.4W

We managed to push the unit to 787.4W before it would shut down, gracefully. Overcircuit protection works fine and we experienced no issues.

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
590W	1.0	3.34	1.0	5.05	48.0	12.05	0.2	-11.99	0.5	5.02
190W	18.1	3.28	20.0	4.98	2.0	11.96	0.2	-12.05	0.5	4.99

The Xigmatek unit delivers stable results under our intensive cross load testing with not much fluctuation throughout.

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 Xigmatek unit complied with the ATX standard.

AC Ripple (mV p-p)
DC Load	+3.3V	+5V	+12V	5VSB
174W	10	10	25	5
352W	10	10	30	10
525W	15	10	35	10
700W	15	15	40	10

Ripple results are fantastic throughout and well within the parameters set down in the ATX 12V Ver 2.2 standard. The 12V line registered between 35 and 40 mv as we reached the upper levels of performance. The 3.3V and 5V lines were rock solid.

Efficiency (%)
174W	86.3
352W	88.2
525W	87.3
700W	85.3

The NRP-PC702 exceeds Bronze certification, peaking at 88.2 percent efficiency around 50% load. An excellent set of results for the Xigmatek unit.

Noise (dBA)
174W	19.2
352W	24.2
525W	27.8
700W	35.3

The supply remains quiet until around 75% load when it starts to become audible. At full load the PC702 registers around 35 dBA which is clearly noticeable.

Temperature (c)
	Intake	Exhaust
174W	35	37
352W	37	42
525W	39	48
700W	43	56

As we get nearer to full load the exhaust temperatures increase which is clearly not helped by the rather small heatsinks inside the supply. We feel Xigmatek could have made these 33% larger to really help with cooling efficiency, there is a lot of space in this chassis going to waste.

Maximum load	Efficiency
787.4W	82.8

Pushing the PSU above its rated limits generates an efficiency level of around 82.8%. This is not a viable ‘real world’ situation, but its interesting nonetheless.

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