RASURBO Real & Power 550 W Review 3

RASURBO Real & Power 550 W Review

Ripple Measurements »

Advanced Transient Response Tests

In these tests we monitor the response of the PSU in two different scenarios. First a transient load (10A at +12V, 5A at 5V and 6A at 3.3V) is applied for 50 ms to the PSU, while the latter is working at a 20% load state. In the second scenario the PSU, while working with 50% load, is hit by the same transient load (with the exception now that load at 3.3V is increased by 4A). In both tests, we measure the voltage drops that the transient load causes, using a Labjack that is attached to our loader and the Stingray oscilloscope. In any case voltages should remain within the regulation limits specified by the ATX specification. We must stress here, that the above tests are crucial, since they simulate transient loads that a PSU is very likely to handle (e.g. starting of a RAID array, an instant 100% load of CPU/VGAs etc.) We call these tests “Advanced Transient Response Tests” and they are designed to be very tough to master, especially for PSUs with capacities lower than 500W.

Advanced Transient Response 20%
VoltageBeforeAfterChangePass/Fail
12 V12.008V11.858V1.25%Pass
5 V4.975V4.843V2.65%Pass
3.3 V3.271V3.133V4.22%Fail
5VSB4.992V4.921V1.42%Pass


Advanced Transient Response 50%
VoltageBeforeAfterChangePass/Fail
12 V11.987V11.827V1.33%Pass
5 V4.864V4.708V3.21%Fail
3.3 V3.201V3.053V4.62%Fail
5VSB4.931V4.876V2.35%Pass


The PSU's small capacity was an aggravating factor in these tests. The +12V rail managed to control the applied transient loads and staid well within regulation limits but the minor rails and especially 3.3V suffered, a lot, in these tests. The final verdict here is not good for RAPM550, at least for the minor rails.

Below you will find the oscilloscope screenshots that we took during Advanced Transient Response Testing.

Transient Response at 20% Load



Transient Response at 50% Load



Turn-On Transient Tests

In the next set of tests we measure the response of the PSU in simpler scenarios of transient loads, during the turn on phase of the PSU. In the first test we turn off the PSU, dial 2A load at 5VSB and then switch on the PSU. In the second test, while the PSU is in standby, we dial the maximum load that +12V can handle and we start the PSU. In the last test, while the PSU is completely switched off (we cut off power or switch off the PSU's On/Off switch), we dial the maximum load that +12V can handle and then we switch on the PSU from the loader and we restore power. The ATX specification states that recorded spikes on all rails should not exceed 10% of their nominal values (e.g. +10% for 12V is 13.2V and for 5V is 5.5V).



RAPM550 passed these tests with flying colors since it did not register any voltage overshoots and rise time was constantly within ATX spec limits.
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Nov 24th, 2024 08:53 EST change timezone

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