Enermax NAXN 82+ 750 W Power Supply Review
By Gabriel Torres on May 13, 2011


Introduction

Hardware Secrets Golden Award

The NAXN is the latest power supply series from Enermax, and is subdivided into three sub-series: the NAXN, also known as Tomahawk II, featuring 350 W, 450 W, and 500 W models, with no 80 Plus certification; the NAXN 80+, featuring 350 W, 450 W, 500 W, and 600 W models, with the standard 80 Plus certification; and the NAXN 82+, featuring 750 W and 850 W models, with the 80 Plus Bronze certification and modular cabling system (a feature not available on the models from the other two sub-series.) Let’s see if the new Enermax NAXN 82+ 750 W is a good option.

Enermax NAXN 82+ 750 W power supply
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Figure 1: Enermax NAXN 82+ 750 W power supply

Enermax NAXN 82+ 750 W power supply
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Figure 2: Enermax NAXN 82+ 750 W power supply

The Enermax NAXN 82+ 750 W is 6.3” (160 mm) deep, using a 135 mm sleeve bearing fan on its bottom (Globe Fan S1352512H, maximum of 2,000 rpm, 123 cfm, and 44.1 dBA).

This unit has a modular cabling system with seven connectors (two red for video card power cables and five black for SATA and peripheral power cables), and five cables are permanently attached to the power supply. This power supply comes with the following cables:

All wires are 18 AWG, which is the correct gauge to be used, except the +12 V (yellow) and +3.3 V (orange) wires on the main motherboard cable, which are thicker (16 AWG).

The cable configuration is excellent for a 750 W product. It is important to understand that while the modular video card cables are wrapped in the same nylon sleeve and share the same connector on the power supply side, they are separate cables. The second red connector is left unused on the power supply’s default configuration, allowing you to buy an additional video card cable to connect a third high-end video card without the need of adapters.

Enermax NAXN 82+ 750 W power supply
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Figure 3: Cables

Let’s now take an in-depth look inside this power supply.

A Look Inside the Enermax NAXN 82+ 750 W

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.

In this page we will have an overall look, and then in the following pages we will discuss in detail the quality and ratings of the components used.

Enermax NAXN 82+ 750 W power supply
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Figure 4: Top view

Enermax NAXN 82+ 750 W power supply
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Figure 5: Front quarter view

Enermax NAXN 82+ 750 W power supply
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Figure 6: Rear quarter view

Enermax NAXN 82+ 750 W power supply
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Figure 7: The printed circuit board

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. 

In this power supply, this stage is flawless. It has one X capacitor and two Y capacitors more than the minimum required.

Enermax NAXN 82+ 750 W power supply
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Figure 8: Transient filtering stage (part 1)

Enermax NAXN 82+ 750 W power supply
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Figure 9: Transient filtering stage (part 2)

In the next page we will have a more detailed discussion about the components used in the Enermax NAXN 82+ 750 W.

Primary Analysis

On this page we will take an in-depth look at the primary stage of the Enermax NAXN 82+ 750 W. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses two GBU1005 rectifying bridges connected in parallel on its primary, which are attached to an individual heatsink. These components support up to 10 A at 100° C each, so in theory, you would be able to pull up to 2,300 W from a 115 V power grid. Assuming 80% efficiency, the bridges would allow this unit to deliver up to 1,840 W without burning themselves out. Of course, we are only talking about these components, and the real limit will depend on all the other components in this power supply.

Enermax NAXN 82+ 750 W power supply
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Figure 10: Rectifying bridge

The active PFC circuit uses two IPW60R125P MOSFETs, each supporting up to 25 A at 25° C or 16 A at 100° C in continuous  mode (note the difference temperature makes), or 82 A in pulse mode at 25° C. These transistors present a 125 mΩ resistance when turned on, a characteristic called RDS(on). The lower the number the better, meaning that the transistor will waste less power, and the power supply will have a higher efficiency.

Enermax NAXN 82+ 750 W power supply
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Figure 11: Active PFC transistors

The electrolytic capacitor that filters the output of the active PFC circuit is Japanese, from Chemi-Con, and labeled at 105° C.

In the switching section, two SPP20N60C3 MOSFETs are used, installed in the two-transistor forward configuration. Each one is capable of delivering up to 20.7 A at 25° C or 13.1 A at 100° C in continuous mode, or 62.1 A in pulse mode at 25° C. These transistors present an RDS(on) of 190 mΩ.

Enermax NAXN 82+ 750 W power supply
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Figure 12: Switching transistors

The primary is controlled by the omnipresent CM6800 active PFC/PWM combo controller.

Enermax NAXN 82+ 750 W power supply
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Figure 13: Active PFC/PWM combo controller

Let’s now take a look at the secondary of this power supply.

Secondary Analysis

The Enermax NAXN 82+ 750 W has eight Schottky rectifiers attached to the secondary heatsink.

The maximum theoretical current each line can deliver is given by the formula I / (1 - D) where D is the duty cycle used and I is the maximum current supported by the rectifying diode. As an exercise, we can assume a duty cycle of 30%.

The +12 V output uses four KCQ60A06 Schottky rectifiers (60 A, 30 A per internal diode at 69° C, 0.67 V maximum voltage drop), giving us a maximum theoretical current of 171 A or 2,057 W for this output.

The +5 V output uses two PFR30L45CT Schottky rectifiers (30 A, 15 A per internal diode at 110° C, 0.52 V maximum voltage drop), giving us a maximum theoretical current of 43 A or 214 W for this output.

The +3.3 V output uses another two PFR30L45CT Schottky rectifiers (30 A, 15 A per internal diode at 110° C, 0.52 V maximum voltage drop), giving us a maximum theoretical current of 43 A or 141 W for this output.

Enermax NAXN 82+ 750 W power supply
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Figure 14: The +3.3 V, +5 V, and +12 V rectifiers

This power supply uses a PS223 monitoring integrated circuit, which supports over voltage (OVP), under voltage (UVP), over current (OCP), and over temperature (OTP) protections. This chip has four OCP channels, one for +3.3 V, one for +5 V, and two for +12 V, correctly matching the number of +12 V rails advertised by the power supply manufacturer (two).

Enermax NAXN 82+ 750 W power supply
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Figure 15: Monitoring circuit

The electrolytic capacitors available in the secondary are from Teapo, and are labeled at 105° C.

Power Distribution

In Figure 16, you can see the power supply label containing all the power specs.

Enermax NAXN 82+ 750 W power supply
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Figure 16: Power supply label

This power supply is sold as having two +12 V rails, which is correct, since this unit has two +12 V over current protection circuits (see previous page), and we could clearly see one “shunt” (current sensor) for each +12 V “rail.” See Figure 17. Click here to understand more about this subject.

Enermax NAXN 82+ 750 W power supply
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Figure 17: Shunts

The two +12 V rails are distributed like this:

This distribution is adequate.

How much power can this unit really deliver? Let’s find out.

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 the behavior of the reviewed unit 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 powers listed for each test, you may find a different value than what is posted under “Total” below. Since each output can have a slight variation (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. In the “Total” row, we are using the real amount of power being delivered, as measured by our load tester.

The +12VA and +12VB inputs listed below are the two +12 V independent inputs from our load tester. During this test, the +12VA input was connected to the power supply +12V1 and +12V2 rails, while the +12VB input was connected to the power supply +12V1 rail.

Input

Test 1

Test 2

Test 3

Test 4

Test 5

+12VA

5 A (60 W)

11 A (132 W)

16 A (192 W)

22 A (264 W)

27 A (324 W)

+12VB

5 A (60 W)

10 A (120 W)

16 A (192 W)

21 A (252 W)

27 A (324 W)

+5 V

2 A (10 W)

4 A (20 W)

6 A (30 W)

8 A (40 W)

10 A (50 W)

+3.3 V

2 A (6.6 W)

4 A (13.2 W)

6 A (19.8 W)

8 A (26.4 W)

10 A (33 W)

+5VSB

1 A (5 W)

1.5 A (7.5 W)

2 A (10 W)

2.5 A (12.5 W)

3 A (15 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

150.6 W

315.8 W

454.9 W

615.8 W

751.4 W

% Max Load

20.1%

42.1%

60.7%

82.1%

100.2%

Room Temp.

45.5° C

45.2° C

46.6° C

49.1° C

45.4° C

PSU Temp.

46.6° C

46.8° C

47.3° C

48.4° C

49.8° C

Voltage Regulation

Pass

Pass

Pass

Pass

Pass

Ripple and Noise

Pass

Pass

Pass

Pass

Pass

AC Power

177.6 W

365.5 W

532.0 W

735.0 W

920.0 W

Efficiency

84.8%

86.4%

85.5%

83.8%

81.7%

AC Voltage

115.4 V

113.8 V

112.2 V

109.6 V

106.7 V

Power Factor

0.924

0.97

0.984

0.991

0.994

Final Result

Pass

Pass

Pass

Pass

Pass

The Enermax NAXN 82+ 750 W proved to be a nice mainstream power supply.

Efficiency was high when we pulled between 20% and 80% of the labeled wattage (i.e., between 150 W and 600 W), ranging from 83.8% and 86.4%. At 750 W, efficiency dropped to 81.7%, which is close enough to the 82% minimum required for the 80 Plus Bronze certification.

Voltage regulation was excellent, with all voltages within 3% of their nominal values, including the -12 V output. This means that voltages were closer to their nominal values than required by the ATX12V specification, which says positive voltages must be within 5% of their nominal values and negative voltages must be within 10% of their nominal values.

Noise and ripple levels were always below the maximum allowed, but a little too high at the +12 V outputs when the unit was delivering 750 W for us to consider this unit as “flawless.” Below you can see the results for the power supply outputs during test number five. The maximum allowed is 120 mV for +12 V and -12 V outputs, and 50 mV for +5 V, +3.3 V and +5VSB outputs. All values are peak-to-peak figures.

Enermax NAXN 82+ 750 W power supply
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Figure 18: +12VA input from load tester during test five at 751.4 W (84.6 mV)

Enermax NAXN 82+ 750 W power supply
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Figure 19: +12VB input from load tester during test five at 751.4 W (82.6 mV)

Enermax NAXN 82+ 750 W power supply
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Figure 20: +5V rail during test five at 751.4 W (18.6 mV)

Enermax NAXN 82+ 750 W power supply
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Figure 21: +3.3 V rail during test five at 751.4 W (11.4 mV)

Let’s see if we can pull more than 750 W from this unit.

Overload Tests

Below you can see the maximum we could pull from this power supply. We couldn’t pull more than that because the power supply shut down, showing that its protections were working just fine.

Input

Overload Test

+12VA

30 A (360 W)

+12VB

30 A (360 W)

+5 V

12 A (60 W)

+3.3 V

12 A (39.6 W)

+5VSB

3 A (15 W)

-12 V

0.5 A (6 W)

Total

838.4 W

% Max Load

111.8%

Room Temp.

40.4° C

PSU Temp.

49.5° C

AC Power

1,046 W

Efficiency

80.2%

AC Voltage

105.9 V

Power Factor

0.995

Main Specifications

The main specifications for the Enermax NAXN 82+ 750 W power supply include:

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

Conclusions

The Enermax NAXN 82+ 750 W is a very nice mainstream power supply that will meet the needs of the average user. Efficiency was high, ranging from 83.8% to 86.4% when pulled between 20% and 80% of the labeled wattage (i.e., between 150 W and 600 W), dropping to 81.7% at 750 W. Voltages were always inside the proper range, as were the noise and ripple levels. All this means that this is a safe power supply that won’t fry or overload your components.

Another highlight of the NAXN 750 W is that it allows you to buy an additional cable with two six/eight-pin connectors for video cards to make it compatible with three high-end video cards.

The main competitors for this unit are the Antec High Current Gamer (which is more expensive), the PC Power & Cooling Silencer Mk II 750 W (same price), and the XFX PRO 750 W (same price). The Enermax NAXN 750 W has an advantage against these other products having a modular cabling system. The XFX PRO 750 W has the advantage of lower noise and ripple levels, while the PC Power & Cooling Silencer Mk II 750 W, an 80 Plus Silver model, has the advantage of presenting higher efficiency. They are all good products, and the final decision of which unit to buy will depend on which of those features you think are more important.

Originally at http://www.hardwaresecrets.com/article/Enermax-NAXN-82+-750-W-Power-Supply-Review/1275


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