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Cooler Master MasterWatt 550W Power Supply Review

Author: Lee Garbutt
Manufacturer: Cooler Master

Efficiency, Differential Temperature and Noise

Efficiency

Efficiency is defined by the power output divided by the power input and is usually expressed as a percentage.  If a PSU were a 100% efficient (which none are) 550 watts of AC power going in would result in 550 watts of DC power coming out (with no waste heat to dissipate).  In the real world there are always inefficiencies and power is lost in the form of heat during the conversion process. Newer revisions to the ATX12V Power Supply Design Guide V 2.2 have continued to increase the efficiency recommendations for PC switching mode power supplies and now lists both required and recommended minimum efficiencies.

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We measured the AC power input to the MasterWatt 550W PSU with an Extech power analyzer while the total DC load was found by adding all the individual +3.3V, +5V, +12V, -12V and +5VSB loads together.  

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The overall efficiency of the MasterWatt 550W power supply is good and meets the criteria for 80 Plus Bronze certification, even while operating on 120VAC and at elevated temperatures.

80 Plus Program

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    Note: Tests conducted at room temperature (25°C)

Differential Temperature and Noise Levels

To simulate a demanding environment, some of the warm exhaust air from the PSU under test is recirculated back to the intake through a passive air duct, which allows the PSU air inlet temperature to increase with load, up to 40°C.  

The differential temperature across the power supply was calculated by subtracting the internal case air temperature (T in) from the temperature of the warm exhaust air flowing out the back of the power supply (T out).  

Thermocouples were placed at the air inlet and exhaust outlet. The ambient room air temperature was 23ºC (74ºF) +/- 0.5ºC during testing.

T out = temperature of air exhausting from power supply
T in = temperature of air entering power supply
Delta T = T out - T in

Sound pressure level readings were taken 3’ away from the rear of the case in an otherwise quiet room.  The ambient noise level was ~27 dBA.

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*Fan not spinning

The MasterWatt 550W PSU started out dead-quiet with no fan rotation and stayed that way through the 20% load mark with relatively cool room air. When we started the 50% load test the cooling fan immediately started spinning and gradually increased to where the noise became noticeable at full load but never became subjectively loud.

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(Courtesy of Cooler Master)


December 3, 2017 | 10:17 PM - Posted by Pink Gnome (not verified)

Surprisingly good for the price. Is there really any practical difference in functionality of any system components between this powersupply and, say, seasonic platinum 550 watt?

December 4, 2017 | 12:22 PM - Posted by Lee Garbutt

Good question. The practical functionality is similar (they both convert AC mains power to the DC voltages required for a PC to operate) but how they do it, how well they do it, and potentially for how long they  keep doing may be quite different. The MasterWatt PSU is a mainstream PSU targeted towards the mass market/average user while the Seasonic Platinum PSU is targeted towards PC enthusiasts looking for a premium PSU.

Compared to the MasterWatt, a Seasonic Platinum PSU uses a more sophisticated design, more components, higher quality components, and includes a longer warranty. These differences result in higher efficiency, better voltage regulation, and reduced AC ripple and noise on the DC outputs, which can potentially make your system more stable and live longer.

December 4, 2017 | 09:11 PM - Posted by Pink Gnome (not verified)

Thanks for the detailed answer!

December 4, 2017 | 01:13 AM - Posted by Cyric (not verified)

I would like to know the OEM for this supply. Coolermaster has a history of using seasonic as an oem which is a good thing.

December 4, 2017 | 12:25 PM - Posted by Lee Garbutt

No, the MasterWatt 550W is not made by Seasonic. Cooler Master appears to be using HEC (based in Taiwan) as the OEM for the MasterWatt series.

December 21, 2017 | 01:43 AM - Posted by Tech We Love (not verified)

Could you test room temperatures at the different watt % usages ? I would like to know how much the room temp rises at each level of power usage.

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