Hot Test Results (~45C Ambient)

The overall performance of all PC PSUs typically degrades once the ambient temperature rises, with various aspects affecting the magnitude of the drop. The average performance drop of the Kratos M1-750W is, for the most part, not bad for an 80Plus Bronze certified platform but the drop does become severe when the unit is heavily loaded, suggesting very high thermal stress. With an ambient temperature of about 45°C, the energy conversion efficiency drops to 85.5% for an input voltage of 230 VAC or to 84.3% for an input voltage of 115 VAC. The level of the drop is nearly tripled for loads greater than 90%.

As expected, the high ambient temperature means that the fan of the Kratos M1-750W will spin at high speeds even if the unit is lightly loaded. This is both due to the higher energy losses and the simplicity of this unit’s thermal control circuitry. The speed of the fan keeps increasing alongside with the load, trying to maintain operational temperatures within the unit. It reaches its maximum speed when the load is at about 600 Watts, beyond which point there is nothing more the fan itself can do. We should note that the design of the chassis allows hot air to escape within our hotbox (or a PC case, under normal working circumstances), limiting the efficiency of the cooling design because it forces the fan to intake the hot air it was just expelled from the numerous holes of the unit.

As we mentioned above, the high ambient temperature forces a high fan speed even if the unit is lightly loaded. The fan will generate more than 40 dB(A) even at minimum load, with that figure constantly increasing until the load is at about 600 Watts, at which point the fan reaches its maximum speed. At loads higher than 600 Watts, the internal temperatures of the Kratos M1-750W rise at a higher rate, reaching highly uncomfortable figures and explaining the extreme thermal stress that the unit’s components are exhibiting during these tests.

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