OCZ Z Series 1000 W Power Supply Review
By Gabriel Torres on March 4, 2010
OCZ Z Series is the 80 Plus Gold-certified power supply family from OCZ, and so far they released an 850 W and a 1,000 W model. Let’s see if the 1000 W model will live up to the expectation.
The OCZ Z Series 1000 W is manufactured by Highpower.
OCZ Z Series 1000 W is very small for a kilowatt product, being 6 ¼” (160 mm) deep, using a 135 mm fan on its bottom and active PFC circuit, of course. This is the exact same size of the 850 W model, by the way.
The modular cabling system has eight connectors, four yellow for video cards and four black for SATA and peripheral power connectors. This unit comes with five cables permanently attached to the power supply. All cables use 18 AWG wires, except the main motherboard cable, which use thicker 16 AWG conductors.
The cables included are:
The difference between the 850 W and the 1000 W here is the presence of two extra video card power cables (the ones permanently attached to the unit) on the 1000 W model; the rest is identical. Therefore this power supply brings enough cables for you to build a high-end system with up to three video cards that require two power connectors each and 12 SATA devices.
Now let’s take an in-depth look inside this power supply.
We decided to disassemble this power supply to see what it looks like inside, how it is designed, and what components are used. Please read our Anatomy of Switching Power Supplies tutorial to understand how a power supply works and to compare this power supply to others.
This page will be an overview, and then in the following pages we will discuss in detail the quality and ratings of the components used. Here we could see that the printed circuit board used on the 1000 W model is exactly the same one used on the 850 W. During the review we will point out which components were upgraded.
As we have mentioned in other articles and reviews, the first place we look when opening a power supply for a hint about its quality, is its filtering stage. The recommended components for this stage are two ferrite coils, two ceramic capacitors (Y capacitors, usually blue), one metalized polyester capacitor (X capacitor), and one MOV (Metal-Oxide Varistor). Very low-end power supplies use fewer components, usually removing the MOV and the first coil.
This power supply is flawless on this stage, with two Y capacitors and one X capacitor more than the minimum required, plus one X capacitor after the rectifying bridges.
In the next page we will have a more detailed discussion about the components used in the OCZ Z Series 1000 W.
On this page we will take an in-depth look at the primary stage of OCZ Z Series 1000 W. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.
This power supply uses two GBJ2506 rectifying bridges connected in parallel in its primary, each one supporting up to 25 A at 100° C with a heatsink is used, which is the case (without a heatsink this limit drops to 4 A). At 115 V this unit would be able to pull up to 5,750 W from the power grid; assuming 80% efficiency, the bridges would allow this unit to deliver up to 4,600 W without burning themselves out. ¡ay caramba! Talk about overspecification! Of course, we are only talking about these components, and the real limit will depend on all the other components in this power supply. These components were upgraded from the 850 W version, which uses two 15 A bridges here.
On the active PFC circuit three SPW24N60C3 power MOSFET transistors are used, each one capable of delivering up to 24.3 A at 25° C or 15.4 A at 100° C in continuous mode (note the difference temperature makes), or up to 72.9 A in pulse mode at 25° C. These transistors present a resistance of 160 mΩ when turned on, a characteristic called RDS(on). This number indicates the amount of power that is wasted, so the lower this number the better, as less power will be wasted thus increasing efficiency. This section was upgraded from the 850 W version, which uses only two transistors instead of three.
This power supply uses two electrolytic capacitors to filter the output from the active PFC circuit. The use of more than one capacitor here has absolute nothing to do with the “quality” of the power supply, as laypersons may assume (including people without the proper background in electronics doing power supply reviews around the web). Instead of using one big capacitor, manufacturers may choose to use two or more smaller components that will give the same total capacitance, in order to better accommodate space on the printed circuit board, as two or more capacitors with small capacitance are physically smaller than one capacitor with the same total capacitance. OCZ Z Series 1000 W uses two 390 µF x 400 V capacitors in parallel; this is equivalent of one 780 µF x 400 V capacitor. These capacitors are Japanese, from Rubycon and labeled at 105° C, the best configuration possible.
In the switching section, another two SPW24N60C3 power MOSFETs are used on the traditional two-transistor forward configuration. The specs for these transistors are published above. These are the same transistors used on the 850 W model.
The switching transistors are controlled by the famous PFC/PWM combo controller CM6800. This was a surprise, as we didn’t expect an 80 Plus Gold using this controller, as many other manufacturers are moving to other designs in order to increase efficiency (e.g., resonant design).
In summary on the 1000 W model the bridges were upgraded and one additional transistor was added on the active PFC circuit in relation with the 850 W model.
Now let’s take a look at the secondary of this power supply.
This power supply is based on a DC-DC design, meaning that it is basically a +12 V power supply with the +5 V and +3.3 V outputs being generated using two separated switching power supplies connected to the +12 V rail. This design is proving to be the best choice in order to achieve high efficiency. On top of that OCZ Z Series uses a synchronous design to generate its +12 V output. In this kind of design the rectifiers are replaced with MOSFET transistors in order to increase efficiency.
Eight AP95T07GP MOSFETs are used to produce the +12 V rail, four for the direct rectification and four for the “freewheeling” part. Each one supports up to 80 A at 25° C or 70 A at 100° C in continuous mode, or up to 320 A at 25° C in pulse mode, with an RDS(on) of only 5 mΩ. This is exactly the same configuration used on the 850 W model.
The maximum theoretical current each line can deliver is given by the formula I / (1 - D), where D is the duty cycle used and I is the maximum current supported by the rectifying diode. Just as an exercise, we can assume a typical duty cycle of 30%.
The +12 V rail is also used by the +5 V and +3.3 V rails as well; if all power was pulled from the +12 V rail alone, we are talking about a maximum theoretical current of 400 A or 4,800 W at 100° C. Holy moly!
Of course this is a theoretical number and we are just making an exercise here. The real amount of current/power each output can deliver is limited by other components.
In Figure 14, you can see one of the DC-DC modules (the unit has one for the +5 V output and one for +3.3 V output). It has four IPD060N03L MOSFET transistors – each one capable of handling up to 50 A at 100° C with a 6 mΩ RDS(on) – and one APW7073 PWM controller. These modules are identical to the ones used on the 850 W version of this power supply.
The outputs are monitored by a PS224 integrated circuit, which supports OVP (over voltage protection), UVP (under voltage protection) and OCP (over current protection). Any other protection this power supply may have is implemented outside this circuit.
All capacitors from the secondary are also Japanese, from Chemi-Con.
In Figure 16, you can see the power supply label containing all the power specs.
As you can see, according to the label this unit has a single +12 V rail, so there is not much to talk about here.
Now let’s see if this power supply can really deliver 1000 W.
We conducted several tests with this power supply, as described in the article Hardware Secrets Power Supply Test Methodology.
First we tested this power supply with five different load patterns, trying to pull around 20%, 40%, 60%, 80%, and 100% of its labeled maximum capacity (actual percentage used listed under “% Max Load”), watching how the reviewed unit behaved under each load. In the table below we list the load patterns we used and the results for each load.
If you add all the power listed for each test, you may find a different value than what is posted under “Total” below. Since each output can vary slightly (e.g., the +5 V output working at +5.10 V), the actual total amount of power being delivered is slightly different than the calculated value. On the “Total” row we are using the real amount of power being delivered, as measured by our load tester.
The +12VA and +12VB inputs listed below are the two +12 V independent inputs from our load tester. During this test both inputs were connected to the power supply single rail (+12VB input was connected to the power supply EPS12V connector and all other cables were connected to the load tester +12VA input).
8 A (96 W)
14 A (168 W)
22 A (264 W)
30 A (360 W)
33 A (396 W)
8 A (96 W)
14 A (168 W)
22 A (264 W)
28 A (336 W)
33 A (396 W)
2 A (10 W)
6 A (30 W)
8 A (40 W)
10 A (50 W)
22.5 A (112.5 W)
2 A (6.6 W)
6 A (19.8 W)
8 A (26.4 W)
10 A (33 W)
22 A (72.6 W)
1 A (5 W)
2 A (10 W)
2.5 A (12.5 W)
3 A (15 W)
3.5 A (17.5 W)
0.5 A (6 W)
0.5 A (6 W)
0.5 A (6 W)
0.5 A (6 W)
0.5 A (6 W)
% Max Load
Fail on +3.3 V
Ripple and Noise
Fail on -12 V
Before analyzing our results, we have to explain that we were limited by our equipment. Our load tester doesn’t allow us to pull more than 33 A from each of its +12 V inputs and, because of that, we couldn’t do the 1000 W test (test five) the way we wanted. We always try to pull more from +12 V and less from +5 V and +3.3 V, because this distribution better reflects the usage of a modern PC, since the +12 V output is used to feed the CPU and the video cards. Because of this limitation we had to increase current/power on +5 V and +3.3 V above the level we would have used if our tester didn’t have such limitation.
The +3.3 V output presented 3.06 V during this test, below the minimum allowed (3.135 V). However, we should not consider this a total failure, because, as explained, we were pulling more current/power from +3.3 V than we normally do.
The good thing is that OCZ Z Series 1000 W can really deliver its labeled wattage at high temperatures, always presenting a sky-high efficiency, between 87.8% and 89.6% when we pulled up to 800 W from it. At 1000 W efficiency dropped to 84.3%, still a very decent number.
80 Plus Gold certification, however, promises that this power supply would be able to show efficiency of at least 87% under light (20%, 200 W in the case of this unit) and full (100%, 1000 W) loads, and efficiency of at least 90% under typical (50%, 500 W in the case of this unit) load. As you can see there is a gap between what is promised and what this unit can really deliver under full load, mainly because Ecos Consulting, the company behind 80 Plus certification, tests power supplies at 23° C (which we think is unrealistic) and we test power supplies with a room temperature of at least double that (efficiency drops with temperature). Click here to understand more about this problem.
Voltage regulation was very good, with all voltages within 3% of their nominal values (i.e., voltages closer to their “face value” than required by the ATX12V specification that allows a 5% tolerance for all positive voltages and 10% for -12 V). The exception was for +3.3 V during test four (at 3.19 V it was still inside the 5% margin) and five (as explained above).
Noise and ripple was always low, except on -12 V output, which passed the maximum allowed during test five (122.6 mV). Below you can see the results for the other outputs on the same test. The maximums allowed are 120 mV for +12 V and -12 V and 50 mV for +5 V and +3.3 V. All values are peak-to-peak figures.
Let’s see if we could pull even more from OCZ Z Series 1000 W.
The maximum we could pull from this power supply with it still working is shown below. The problem here was that our load tester can only show up to 999.9 W on its display and because the unit was delivering more than 1,000 W we couldn’t read the exact amount of power being delivered and thus making it impossible for us to calculate efficiency. Notice also that we were once again limited by our equipment, because we maxed out all outputs from our load tester, which has a 33 A limit on each output. This unit can probably deliver even more power.
33 A (396 W)
33 A (396 W)
33 A (165 W)
33 A (108.9 W)
4 A (20 W)
0.5 A (6 W)
1,072 W (Estimated)
OCZ Z Series 1000 W power supply specs include:
* Researched at Newegg.com on the day we published this review.
Right now OCZ has the advantage of being the only manufacturer with high-wattage 80 Plus Gold-certified power supplies on the market. If you have a lot of money and are looking for a high-end 1,000 W power supply, Z Series 1000 W may be an option. This is definitely not a product for users with tight budgets, though.
Internally we discovered that Z Series 1000 W is based on the same project as the 850 W version but with one additional active PFC transistor and upgraded rectifying bridges.
We saw efficiency between 87.8% and 89.6% when we pulled up to 800 W from it. But at 1000 W efficiency dropped to 84.3%, but this may also be caused by the different load pattern we had to use to overcome the limitation in our load tester (see our full test results for a better explanation).
At 1000 W we also saw noise level a little bit above the maximum allowed at -12 V and the +3.3 V output at only 3.06 V (while the minimum allowed is 3.135 V). Unfortunately these two flaws prevent us from recommending this unit. Carrying a heavy price tag (USD 260 - USD 290), we expected to see a flawless product, even though we know that almost no user will pull anywhere near 1000 W and thus these flaws won’t be apparent.
Updated on March 12, 2010: OCZ has just dropped the price of this power supply to USD 244 at Newegg.com (USD 214 after a mail-in rebate), which is also offering free shipping now. This improved a lot the cost/benefit ratio of this product.