Products > Test Equipment
ARRAY electronic loads
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T4P:
You can find them all over at taobao.
saturation:
There are several threads discussing China branded e-loads so I'll summarize points.  Rufus suggests the brands mentioned have much similarity, one thread suggests the BK/Itech/Maynuo/ older Array model are designed by the same person, but I think others are distant copies, some changes don't look optimally thought out, but they seem cheaper to implement.  So for example, the Beich lacks a quality ethos you see in common with BK, Itech, Maynuo or Array.

Here's a comparison of Rufus' Beich CH8710B photo, a clearer photo of an Array [both rated at 150W], and a screen grab from Dave's BK 8500 review [300W].  Sorry its big, but the details are needed to contrast the 3.

The most obvious on the PCBs are thermal management strategies.  The BK and Array use 2 sets of forced cooling heatsinks, while the Beich, rated for the same wattage as the Array, uses one.  It may not be a problem if the fan cfm is >=2x a single Array set, but clearly the Beich case is missing one set of fan/sinks.

Since all 3 claim to have thermal overload protection, if the fans can't handle the load I presume the load with be cut off until they cool down, so if the Beich's copied those features it has a backup plan since it relies on a single fan for all its cooling. 

On both the Array and BK units, the low-ohm power resistors [ the twisted coils of wire in the BK] and heat sinked TO220 device are within the airflow stream of the fans.  There are cutout vents on the side of the BK for intakes, as well as a ventilated bottom chassis.  On the Array, the vents are on the bottom of the PCB both as powered intake fans and passive holes.

On the Beich, while the bottom seems quite 'open' to ambient, the fan is on the opposite side of the input resistors [ the yellow A in the photo], and resistors on the load board marked C, are on top of the PCB, these resistors will have to rely on indirect airflow for cooling.   Beich could have put the single load module on the right side to help cool down those resistors.  On the Array, similar functioning resistors on the load board marked a,b are on the bottom of the PCB, are not visible because they are in the airflow stream of the fans.

In thermal management, overdesign is best, because heat dissipation will suffer drastically if ambient temperature is higher [ such as in hot climates] or obstructions to vents [ such as placing the unit against a wall]. 


Safety

Since few are UL, ETL, TUV etc.,  certified one has to rely on the CE mark or doing one's own due diligence to determine what limitations to put on these eloads.

Both the BK and Beich have line voltage switched on the PCB; the Array uses a separate switch and only low voltage appear on the PCB.  Not big issues, but its safer to keep line voltage separate from low voltage lines in case high voltage transients in mains voltage enters the unit.

Both Array and BK add MOVs as surge input protection, and the binding posts, which potentially can contain higher voltages, are kept free of other lines as potential arc points, the only wire nearest it is a ground wire quite some distance away.   The Beich seems to only have high voltage capacitors on the input, and there are a bunch ribbon cable crossing near its binding posts; one could move them away a bit as an arc may not be lethal to the operator but more lethal to the control electronics.

Modern high voltage design prefers cutout to control line clearances on PCBs.  Eyeballing, the creepage distances on the Array and Beich are acceptable but adding cutouts would be better.

The Array has surprising design elements that provide safety in redundancy but at greater cost.

For example, Array has two thermal sensors for each load cell, 2 fans for each cell.  I'm not sure but suspect each fan is controlled by each cell.
 
The Array design takes trouble to add separate ground wires to the chassis walls, and terminate them to the same ground point.  This insures that the ground lines have lowest impedance path, rather than bolting it to the chassis.

I'm intrigued by the x6 MOSFETs at the input.  I'm not sure how its configured as a switch, but it gives a banked series rating of 330V at 110A.  I'm guessing its either a high voltage reverse input protection but how it does it I'm still examining, and will report back.  A similar configuration is not present on the BK or Beich.

So in conclusion, even if Beich units copy another's design there is a big difference in implementation, considering the list price is often similar to Arrays. 

The Array seems very competent in hardware for what its designed to do, and for small labs, its use of through hole, and fairly generic parts makes its easier to service DIY.  More later as I finished a detailed review and performance and finally safety test.


robrenz:
Wow saturation  :o  so much for BK just being a rebrand. Thanks for the pictorial comparison.
saturation:
I'm fairly intrigued by these e-loads, it has the look of being done by a very small team, even one man [ kmel in another thread suggests the designer Xiao Tony was formerly at Array, and the 3710a looks like an early version of models later of Itech/BK/Maynuo.]

However, for bang for buck, the Array is looking like a very decent box if you don't need to test systems using constant voltage, and can deal with its buggy software.

T4P provided some links to vendors in China per se, via taobao.com.  Units from Beich, Maynuo and Array for the same wattage are priced near the same, even if Array is an older design.  I think its main feature is its likely built like a tank and can take abuse, and Array is the only model you can get in the USA directly as OEM for other brands, like TekPower. 



--- Quote from: robrenz on September 17, 2012, 03:50:17 pm ---Wow saturation  :o  so much for BK just being a rebrand. Thanks for the pictorial comparison.

--- End quote ---
saturation:
I've just posted a hardware teardown of the Array 3710a dc electronic load.  My model is rebadged as Tekpower.

http://www.flickr.com/photos/igsaturation/sets/72157631565608376/

There are 31 photos so the above link is faster.  It would be best to comment on this thread so the discussion has a larger audience than the Flickr site.  I'll steer any comments on Flickr back here or mirror replies.

Since I have confidence the unit is built well, its now undergoing stress testing and I'll post a functional review later on this thread.

 
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