Introduction

Nexus is a Dutch company and their power supplies can be easily found in the United States and in Europe, of course. Today we are going to take a look at their 630 W RX-6300 power supply, which comes with a modular cabling system, a single-rail design and an ultra low noise fan. Is it a good buy? Let’s see.

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Figure 1: Nexus RX-6300 power supply.

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Figure 2: Nexus RX-6300 power supply.

Nexus RX-6300 is 6 19/64” (160 mm) deep, using a 135 mm fan on its bottom and featuring active PFC, of course. It has a modular cabling system, but some of the cables are permanently attached to the power supply (these cables have a nylon protection that comes from inside the power supply case). Also, the modular cabling system has eight connectors, but the power supply comes with only five cables. This power supply comes with the following cables:

• Main motherboard cable with a 20/24-pin connector (permanently attached to the power supply).
• One cable with one EPS12V connector that can be transformed in two ATX12V connectors (permanently attached to the power supply).
• One ATX12V cable (permanently attached to the power supply).
• One cable with one six/eight-pin auxiliary power connector for video cards (permanently attached to the power supply).
• One cable with one six-pin auxiliary power connector for video cards (modular cabling system).
• Two cables with three SATA power connectors each (modular cabling system).
• Two cables with three standard peripheral power connectors and one floppy disk drive power connector each (modular cabling system).

The cable configuration from RX-6300 is perfect for a 630 W product.

The cables that are permanently attached to the power supply are 18 1/8” (46 cm) long, and the cables from the modular cabling system are a little bit longer, with 19 ¾” (50 cm) between the power supply and the first connector on the cable. Peripheral connectors have 5 7/8” (15 cm) between them, but SATA connectors have 7 7/8” (20 cm) between them, which is great.

All cables use 18 AWG wires, which is the correct gauge to be used.

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Figure 3: Cables.

Now let’s take an in-depth look inside this power supply.

A Look Inside The Nexus RX-6300

We decided to disassemble this power supply to see what it looks like inside, how it is designed, and what components are used. Please read our Anatomy of Switching Power Supplies tutorial to understand how a power supply works and to compare this power supply to others.

This page will be an overview, while in the following pages we will discuss the quality and ratings of the components used in detail.

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Figure 4: Overall look.

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Figure 5: Overall look.

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Figure 6: Overall look.

Transient Filtering Stage

As we have mentioned in other articles and reviews, the first place we look when opening a power supply for a hint about its quality is its filtering stage. The recommended components for this stage are two ferrite coils, two ceramic capacitors (Y capacitors, usually blue), one metalized polyester capacitor (X capacitor), and one MOV (Metal-Oxide Varistor). Very low-end power supplies use fewer components, usually removing the MOV and the first coil.

On this power supply this stage is flawless: it has two X capacitors and two Y capacitors more than the minimum required.

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Figure 7: Transient filtering stage (part 1).

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Figure 8: Transient filtering stage (part 2).

In the next page we will have a more detailed discussion of the components used in the Nexus RX-6300.

Primary Analysis

On this page we will take an in-depth look at the primary stage of Nexus RX-6300. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses one GBU1006 rectifying bridge, which supports up to 10 A at 100º C, if a heatsink is used, which is the case (without a heatsink the current limit drops to 3.2 A). So in theory you would be able to pull up to 1,150 W from a 115 V power grid; assuming 80% efficiency, this bridge would allow this unit to deliver up to 920 W without burning. Of course we are only talking about this component and the real limit will depend on all other components from the power supply.

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Figure 9: Rectifying bridge.

The active PFC circuit uses two IXTQ26N50P power MOSFET transistors, each one capable of delivering up to 26 A at 25º C in continuous mode (unfortunately the manufacturer does not publish the maximum current at 100º C) or 78 A in pulse mode at 25º C. These transistors present a 230 mΩ resistance when turned on, a characteristic called RDS(on). The lower this number the better, meaning that the transistors will waste less power and the power supply will achieve a higher efficiency.

The electrolytic capacitor in charge of filtering the output from the active PFC circuit is Taiwanese from Teapo and labeled at 85º C.

In the switching section, two SPW16N50C3 power MOSFET transistors are used on the traditional two-transistor forward configuration. Each transistor supports up to 16 A at 25º C or 10 A at 100º C (note the difference temperature makes) or 48 A in pulse mode at 25º C, presenting an RDS(on) of 280 mΩ.

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Figure 10: +5VSB switching transistor, one of the active PFC transistors and switching transistors.

This power supply uses the famous CM6800 active PFC/PWM combo controller soldered on the solder side of the printed circuit board.

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Figure 11: Active PFC/PWM combo controller.

Now let’s take a look at the secondary of this power supply.

Secondary Analysis

This power supply uses a partial synchronous design for rectifying the +12 V output, using an FDP038AN MOSFET (80 A at 151º C, 3.5 mΩ RDS(on)) for the direct rectification and a PFR60L45PT Schottky rectifier (60 A, 30 A per internal diode) for the “freewheeling” part of the rectification.

For the +5 V output one S30D40C Schottky rectifier is used, which supports up to 30 A (15 A per internal diode at 125º C) and presents a maximum voltage drop of 0.55 V. This gives us a maximum theoretical current of 21 A or 107 W for the +5 V output.

The +3.3 V output uses another S30D40C Schottky rectifier, presenting a maximum theoretical power of 71 W.

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Figure 12: Rectifiers.

This power supply uses a WT751002 monitoring integrated circuit, which is in charge of the power supply protections. Unfortunately the manufacturer from this component does not publish the datasheet for this integrated circuit, so we couldn’t check what protections it really supports.

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Figure 13: Monitoring circuit.

Electrolytic capacitors from the secondary are also Taiwanese, from Teapo and labeled at 105º C.

Power Distribution

In Figure 14, you can see the power supply label containing all the power specs.

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Figure 14: Power supply label.

This power supply uses a single-rail design, so there is not much to talk about here.

Now let’s see if this power supply can really deliver 630 W.

Load Tests

We conducted several tests with this power supply, as described in the article Hardware Secrets Power Supply Test Methodology.

First we tested this power supply with five different load patterns, trying to pull around 20%, 40%, 60%, 80%, and 100% of its labeled maximum capacity (actual percentage used listed under “% Max Load”), watching how the reviewed unit behaved under each load. In the table below we list the load patterns we used and the results for each load.

If you add all the power listed for each test, you may find a different value than what is posted under “Total” below. Since each output can vary slightly (e.g., the +5 V output working at 5.10 V), the actual total amount of power being delivered is slightly different than the calculated value. On the “Total” row we are using the real amount of power being delivered, as measured by our load tester.

The +12V1 and +12V2 inputs listed below are the two +12 V independent inputs from our load tester. During this test both were connected to the single +12 V rail from this power supply.

Input	Test 1	Test 2	Test 3	Test 4	Test 5
+12V1	5 A (60 W)	10 A (120 W)	14.5 A (174 W)	19 A (228 W)	24 A (288 W)
+12V2	4.5 A (54 W)	9.5 A (114 W)	14 A (168 W)	19 A (228 W)	24 A (288 W)
+5V	1 A (5 W)	2 A (10 W)	4 A (20 W)	5 A (25 W)	6 A (30 W)
+3.3 V	1 A (3.3 W)	2 A (6.6 W)	4 A (13.2 W)	5 A (16.5 W)	6 A (19.8 W)
+5VSB	1 A (5 W)	1 A (5 W)	1.5 A (7.5 W)	2 A (10 W)	2.5 A (12.5 W)
-12 V	0.5 A (6 W)	0.5 A (6 W)	0.5 A (6 W)	0.5 A (6 W)	0.5 A (6 W)
Total	134.8 W	264.4 W	390.3 W	513.3 W	632.4 W
% Max Load	21.4%	42.0%	62.0%	81.5%	100.4%
Room Temp.	46.1º C	45.9º C	47.2º C	49.3º C	49.2º C
PSU Temp.	47.0º C	47.8º C	48.9º C	50.6º C	52.3º C
Voltage Regulation	Pass	Pass	Pass	Pass	Pass
Ripple and Noise	Pass	Pass	Pass	Pass	Pass
AC Power	159.8 W	305.3 W	453.1 W	604.6 W	760.4 W
Efficiency	84.4%	86.6%	86.1%	84.9%	83.2%
AC Voltage	113.3 V	111.6 V	110.3 V	108.8 V	108.8 V
Power Factor	0.970	0.990	0.995	0.997	0.997
Final Result	Pass	Pass	Pass	Pass	Pass

Nexus RX-6300 can really deliver 630 W at practically 50º C.

Efficiency was high in all load patterns, staying above 86% when we pulled between 40% and 60% from its labeled capacity (between 252 W and 378 W) and at around 85% when we pulled 80% from its labeled capacity (504 W). At light load (20% load, i.e., 126 W) efficiency was still high at 84.4% and we were happy to see an 83.2% efficiency at full load.

Interesting enough this unit is not 80 Plus certified, but it could easily get the 80 Plus Bronze certification if the manufacturer wanted to.

Voltage regulation was another highlight from this product, with all voltages within 3% from their nominal values, i.e., voltages close to their nominal values that what is allowed (5%). This includes the -12 V output, which usually doesn’t like to stay so close to its nominal value. +5 V output exit this tight margin by only 0.01 V during tests one and two.

And finally we have noise and ripple, which were low all the time. Below you can see the results for test number five. As we always point out, the limits are 120 mV for +12 V and 50 mV for +5 V and +3.3 V and all numbers are peak-to-peak figures.

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Figure 15: +12V1 input from load tester at 632.4 W (63.8 mV).

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Figure 16: +12V2 input from load tester at 632.4 W (63.4 mV).

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Figure 17: +5V rail with power supply delivering 632.4 W (21.4 mV).

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Figure 18: +3.3 V rail with power supply delivering 632.4 W (19.6 mV).

Now let’s see if we could pull more than 630 W from this unit.

Overload Tests

If we tried to pull more than 52 A from the single +12 V rail this power supply would shut down, showing that over current protection (OCP) was present and active. Below you can see the maximum we could pull from this power supply with it still working within specs. If we tried to pull more than that the unit would shut down, showing that one of the power supply protections entered in action.

Input	Maximum
+12V1	26 A (312 W)
+12V2	26 A (312 W)
+5V	24 A (120 W)
+3.3 V	24 A (79.2 W)
+5VSB	3 A (15 W)
-12 V	0.5 A (6 W)
Total	840.4 W
% Max Load	133.4%
Room Temp.	44.4º C
PSU Temp.	49.6º C
AC Power	1,116 W
Efficiency	75.3%
AC Voltage	103.1 V
Power Factor	0.999

Main Specifications

Nexus RX-6300 power supply specs include:

• ATX12V 2.2
• Nominal labeled power: 630 W
• Measured maximum power: 840.4 W at 44.4º C.
• Labeled efficiency: 82% minimum
• Measured efficiency: Between 83.2% and 86.6% at 115 V.
• Active PFC: Yes.
• Modular Cabling System: Yes.
• Motherboard Power Connectors: One 20/24-pin connector, one EPS12V connector that can be broken down into two ATX12V connectors and one ATX12V connector (all permanently attached to the power supply).
• Video Card Power Connectors: One six/eight-pin connector in one cable permanently attached to the power supply, one six-pin connector in one cable available on the modular cabling system.
• SATA Power Connectors: Six in two cables (modular cabling system).
• Peripheral Power Connectors: Six in two cables (modular cabling system).
• Floppy Disk Drive Power Connectors: Two in two cables (modular cabling system).
• Protections: Over voltage (OVP, not tested) and short-circuit (SCP, tested and working) protections. Over current (OCP) protection present and working.
• Warranty: Two years.
• More Information: http://www.nexustechnologyusa.com
• Average price in the US*: USD 120.00.

* Researched at Newegg.com on the day we published this review.

Conclusions

Nexus RX-6300 was a really nice surprise, with efficiency between 83.2% and 86.6% in our tests. Although it is not 80 Plus certified, it achieved a performance that would easily get an 80 Plus Bronze certification, if the manufacturer wanted to.

We could easily deliver its labeled power at 50º C and we could overload this baby up to 840 W without burning it.

All voltages were within a tighter 3% margin while ATX specification allows a 5% margin, meaning that all voltages – including -12 V – were closer to their nominal values than necessary. The exception was when the unit was delivering up to 265 W, when +5 V output got 0.01 V above this tighter margin.

Noise and ripple were low at all timess and, although we didn’t measure it, the noise level produced by the fan was really low.

The number of cables is perfect for a 630 W unit.

The only “problem” we see with this power supply is its price. You can find 750 W power supplies from Seventeam (ST-750P-AF and ST-750Z-AF) costing less, although these models present efficiency a little bit lower than RX-6300.

In summary, it is a good buy for the exigent user, even though we’d like to see it being sold for at least USD 10 less.