Micronics Wizmax G 850W ATX v3.1 PSU Review

Protection Features

Desktop power supply units (PSUs) include several protection features to safeguard both the PSU itself and the connected PC components (motherboard, CPU, GPU, drives, etc.). These protections prevent damage from electrical faults, overloads, or abnormal conditions.

OCP (Normal @ 29.4°C) 12V: 89.80A (126.84%), 12.048V
5V: 31.8A (127.20%), 4.984V
3.3V: 34.3A (137.20%), 3.276V
5VSB: 5.5A (183.33%), 4.924V
OCP (Hot @ 44.4°C) 12V: 87.40A (123.45%), 12.067V
5V: 31.6A (126.40%), 4.983V
3.3V: 34.1A (136.40%), 3.277V
5VSB: 5.4A (180.00%), 4.924V
OPP (Normal @ 29.0°C) 1062.06W (124.95%)
OPP (Hot @ 43.4°C) 1039.06W (122.24%)
OTP ✓ (65°C @ Heat Sink)
SCP 12V to Earth: ✓
5V to Earth: ✓
3.3V to Earth: ✓
5VSB to Earth: ✓
-12V to Earth: ✓
PWR_OK Proper Operation
UVP (Full Load @ 90V)
UVP (No Damage @ 80V)
Conducted Emissions EN55032 & CISPR 32
NLO
Fan Failure Protection
SIP Surge: MOV
Inrush: NTC & Bypass Relay

The OCP triggering points are conservative at 12V under normal and hot conditions, so that I won’t mind a lot the relatively small difference between these two. On the contrary, the minor rails have sky-high OCP triggering points, and to make matters even worse, the difference between normal and high operating temperatures is low.

The over power protection has conservative triggering points, but once more, the difference between normal and hot temperatures is low. I would like to see a larger difference, exceeding 5%. The rest of the essential protection features are present and work well, except for fan failure protection, which is absent. Manufacturers have to quickly realize that fan failure protection is crucial and start implementing it in their designs.

EMC Pre-Compliance at a Glance

Every electronic device, including PSUs, can be an EMI source, which, depending on the amount of EMI emitted, can affect the proper operation of nearby devices. EMI can, in some extreme cases, even render them unusable. Some standards have been established to minimize electromagnetic interference (EMI) noise. The corresponding standards for IT (Information Technology) products are CISPR 32 and its derivativeEN 55032, which applies to products sold in the EU. In the EU, every product bearing the “CE” marking must comply with the EN 55032 standard. CISPR 32 and EN 55032 standards categorize devices into two classes: A and B. Class B equipment is intended for domestic environments. Hence, its permitted EMI emissions are significantly lower than those of A-class devices.

Our equipment for EMI readings:

  • Rohde & Schwarz FPC1500 (loaded with all options)
  • Tekbox TBLC08 LISN
  • Tekbox TBFL1 transient limiter
  • Tekbox EMCview software
CISPR 32 / EN55032 Limits
CISRP 32 / EN 55032 Class A Conducted EMI Limit
Frequency of Emission (MHz) Conducted Limit (dBuV)
Quasi-peak Average
0.15 – 0.50 79 66
0.50 – 30.0 73 60
CISPR 32 / EN 55032 Class B Conducted EMI Limit
Frequency of Emission (MHz) Conducted Limit (dBuV)
Quasi-peak Average
0.15 – 0.50 66 – 56 56 – 46
0.50 – 5.00 56 46
5.00 – 30.00 60 50
CISRP 32 / EN 55032 Class A 10-Meter Radiated EMI Limit
Frequency of Emission (MHz) Field Strength Limit (dBuV/m)
30 – 88 39
88 – 216 43.5
216 – 960 46.5
> 960 49.5
CISRP 32 / EN 55032 Class B 3-Meter Radiated EMI Limit
Frequency of Emission (MHz) Field Strength Limit (dBuV/m)
30 – 88 40
88 – 216 43.5
216 – 960 46.0
> 960 54.0

Please note that the ATX spec allows a 4 dB margin for conducted and radiated emissions. This means that if a PSU exceeds the limits but stays within the 4 dB margin, it meets the corresponding ATX spec requirement (8.1 Emissions).

EMI Results

The PSU’s EMI emissions are under control.

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