Thermaltake Silent PurePower Power Supply

Power enough to run two motherboards at once – Joe

SUMMARY: Very quiet, lots of “overhead” – able to power two motherboards at once.


Auto temperature control: 1300rpm at 25C, 2400rpm at 80C.

The good guys at Thermaltake were nice enough to send a sample the their latest power supply offering, the Thermaltake Silent PurePower 420 watt Power Supply.

The 420 watt model features:

  • Dual Fans
  • Auto temperature control: 1300rpm at 25C, 2400rpm at 80C
  • 3 cables with 3 hard drive plugs and one floppy plug each
  • ATX motherboard plug
  • AUX plug
  • P4 plug
  • Power Supply fan connector

There should be enough plugs for even the most fully featured PC I can think of.

There are some interesting claims made about the “PurePower” series. To understand Thermaltake’s claims, we have to define Power Factor Correction (PFC). I did some searching on the net and found that

Power factor is the percentage of electricity that is being used to do useful work. It is expressed as a ratio. For example, a power factor of 0.72 would mean only 72% of your power was being used to do useful work. Perfect power factor is 1.0,(unity), meaning 100% of the power is being used for useful work.

Power Factor Correction (PFC), then, is the method(s) used to fix the problems that cause power to be wasted.”

Source: DMOZ.

Thermaltake claims that

Non-PFC [power supplies] offers around 0.5~0.6 PF (Power Frequency), 40%~50% power lost. Active PFC provides more efficient PF (Power Frequency), 0.95~0.99, it means only 1%~5% power has gone.

The implication is that a power supply with PFC delivers more usable power than one without it. The only thing I can see, comparing their 420 watt power supplies with and without PFC, is the non-PFC unit is rated at 10 amps and the PFC unit is rated at 8 amps – it takes less power to run the PFC unit.

In the review of Thermaltakes’s power supply, “Power Factor Correction” is a marketing theme of some emphasis. I figured I would get some excellent perspective on it from others more knowledgeable on this than I and our great readers did not disappoint:

John Galazin

I just read your article on the Thermaltake Power Supply. It looks like a pretty nice power supply to me. There’s one thing I wanted to point out about the supposed “PFC” to improve the efficiency of the power supply.

Based on experience with other applications of electronics, I’d bet that the by far greatest advantage of the PFC is significantly reduced heat output. If their efficiency claims are correct, probably a reduction of about one half. All that wasted power is usually dissipated as heat. It looks like they attacked the noise issue at the source.

Theoretically, there can also be costs savings associated with power efficient electronics, but in application the methods required to improve efficiency often cost enough too offset the possible savings.


I recently read your Review of a Thermal take power supply with Power
Factor Correction. You left out a few details though:

Computer power supplies are SWITCHING power supplies, in that they are
never ON all the time; rather, they charge/discharge a bank of inductors &
capacitors VERY quickly, usually at 52kHz (52,000 times per second,) or
higher (the 100kHz range is very common).

Each time a switch transition is
made, either from an ON state to an OFF state or from an OFF state to an ON
state, a HUGE amount of current is released for a VERY short period of time
(called avalanche current.) Because the current is so large, and occurs so
frequently (about once per kHz,) LOTS AND LOTS of radio frequency
interference (RFI) is created.

If the computer power supply DOESN’T have PFC (power factor correction)
circuitry, anything plugged into the sockets next to the computer will
receive the RFI signal.

What does this mean?

It means that the power supplies of other devices plugged in next to
your computer will be loaded down by the RFI. They will have to dissipate
the signal, either in the form of heating up, or by displaying it (as in
TVs,) or transmitting it (as in radios.) For a while several European
nations were considering that any device that gets plugged into a wall
outlet (230VAC 50Hz over there) require PFC circuitry.

If every device had
PFC circuitry, they would cost only SLIGHTLY more, and run significantly
more efficiently, produce FAR LESS HIGH FREQUENCY NOISE. (If no device is
plugged next to your computer, guess who has to dissipate the RFI signal?
Yes, the POWER COMPANY, and NO they don’t like doing it, and it can even
damage equipment).

Making devices more energy efficient would reduce the overall cost of
transmitting electricity, reduce the amount of heat they produce, simplify
Power supply designs, and may eventually totally eliminate the need for the
BIG LOSSY power transformers that we typically see in the power supply
section of Home Theater Audio Amplifiers (Sony uses ones that weigh like
15lbs, and heat up very fast). While many devices already incorporate PFC
circuitry, many cheap ones do not.

Remember, if every device used these integrated circuits (IC chips)
they would be massively produced, dropping their price dramatically.

Part of GOOD PFC circuitry involves using several RF filters which not only
boost the efficiency of the PC power supply, but EFFECTIVELY BOOST the
efficiency of all devices plugged in next to it by allowing them to run
without Radio Frequency Interference.

Hans Petter Faale – Microplex Norge AS

First of all, PF means Power Factor, not Power Frequency.

Second, and more important, “40-50% power lost” is totally misleading.

If your non-PFC PSU with PF=0.65 draws 250VA (during normal operation)
then your PFC PSU with PF=0.99 PSU will draw 164VA. This will give you
slightly less loss in the cables supplying current to the PSU, but the
improvement is of little interest for the average consumer.

PSU with PFC can be of interest for a consumer if they connect the PSU
to a circuit that is loaded very near that circuit’s fuse rating.

Improving PF is first of all of interest for power companies who operate
a grid as this reduce transmission loss (or allows for cables with less
crossection), but then we are talking about tranfering megawatts, not


The part you’re going over actual test result was pretty good, but I have to say your comments about power factor make no sense. Power factor does not affect how much “power” – energy – you actually use and the way it’s written is misleading, as it seems to say you use less power when you use a PSU with an active PFC.

Thermaltake doesn’t appear to have any idea what they’re talking about in regard to power factor of computer PSUs.

Quote from their site:

“Many loads are highly inductive, such a lightly loaded motors and illumination transformers and ballasts. You may want to correct the power factor by adding parallel capacitors. You can also add series capacitors to “remove” the effect of leakage inductance that limits the output current.(Jim Lux -2002).”

This is applicable to inductive or capacitive displacement power factor difference, but it does not apply to distortional power factor loss in computer PSUs and it is one pointless fact.

“Non-PFC offers around 0.5~0.6 PF (Power Frequency), 40%~50% power lost.”

They don’t even realize PF=power factor, not power frequency. 40-50% of power is NOT lost. That is pure bullcrap.

I wrote up a whole technical reason to it here.


Power factor correction is a term applied to the misalignment of the phase angle of the sine wave between input and output voltage and current.
Hence large consumers of electrical power often have very large banks of power factor correction capacitor banks to correct the sine wave phase alignment.

Here in the UK, if you allow too much of a power factor imbalance it costs the electrical supplier hard cash; that is because the “true” power becomes less, as you have already stated.

It is less powered because the current and voltage phases are not in alignment, thus leading or lagging phases require correcting before they are useful. As already stated, true power = 1 – this is where voltage and current phase angles are in line with each other; anything else is less than 100% power.

Examples of phase angle correction that cause problems are fluorescent lights, whereby they require a phase angle differentiation in order to strike. Big rows of fluorescent tubes are major headaches, as believe it or not, are P.C’s; they are often referred to as returning or being dirty to the power line.

So there you have it – maybe more than you wanted to know about “PFC”, but I think it helps to know what it is and how much it should impact your purchasing decision.