EEVblog Electronics Community Forum
Products => Test Equipment => Topic started by: HooRide on October 16, 2012, 07:48:22 pm
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I'm torn between which model e-load to get for my bench, I've never done any DC work above 90V so 120V seems fine and I've built a few power supplies in the 25A 13.8V range so I'm leaning towards the 120VDC 30A max model but if I ever did need to do something with a higher voltage...I might have buyer's remorse. Also, the BK Precision 8500 is easier to find and a few $$$ less expensive than the 8502.
Thoughts?
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Well I would consider including local power grid voltage rectified ( times square root of 2) in the voltage range in case you need to test a PFC preregulator / soft start circuit in a power supply or something... I would personally go for the 500V one :)
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Have you read this whole thread?
https://www.eevblog.com/forum/product-reviews-photos-and-discussion/why-is-bk-precision-still-in-business-bk8500-programmable-load-oem-found/msg137734/#msg137734 (https://www.eevblog.com/forum/product-reviews-photos-and-discussion/why-is-bk-precision-still-in-business-bk8500-programmable-load-oem-found/msg137734/#msg137734)
If not, it is a must read. I learned a whole lot about Eloads and which one I would buy and ways to use it I never thought about, most excellent thread.
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>100VDC is far less common in electronics than electrical and industrial applications, and mostly not for control electronics but to power motors, displays, lasers, etc.,. However, the lowly Array 3710a is rated to 360V, 30A, 150W, and cost far less than the BK. But look into the Maynuo and Itech variations too. Robrenz has great links for more info.
> 100V designs run into problems with dielectric breakdown, arc over, and other nasties when added to high current, high injury and explosive potential [ e.g. plasma]. So whenever possible keep working voltage under 35V, with less worries for current. You can see this philosophy in PC power supplies. If you persue PSU options among big manufacturers like Agilent, there are far more offerings below 100V than above it.
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500V is much and 15A is a lot too. So I voted for 500V / 15A. Some of my recent designs have voltages up to 300V which is why I bought the Array 3710.
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Have you read this whole thread?
https://www.eevblog.com/forum/product-reviews-photos-and-discussion/why-is-bk-precision-still-in-business-bk8500-programmable-load-oem-found/msg137734/#msg137734 (https://www.eevblog.com/forum/product-reviews-photos-and-discussion/why-is-bk-precision-still-in-business-bk8500-programmable-load-oem-found/msg137734/#msg137734)
If not, it is a must read. I learned a whole lot about Eloads and which one I would buy and ways to use it I never thought about, most excellent thread.
I did read most of that thread yesterday and it's curious how many products spanning so many brand names can be attributed to one engineer.
The only reason I would hesitate getting another less-known brand is support. Hardware but more importantly, future software support.
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I would go with the 500V, mainly because 15A is more than i need. (sometimes i want to test 10A 12v psus).
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I'd go for 30A myself. More useful for testing high capacity batteries.
Dave.
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Battery discharging is good point, i'd not considered that.
Mains load vs high current battery discharge and testing. hm.. tough choice
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I'd go for 30A myself. More useful for testing high capacity batteries.
Dave.
In that case the battery voltage must be low. If you want to test a 24V battery you can't go higher than 11A to stay within the 300W limit (say the battery is around 26V in reality).
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aww, it wont do 15A @ 500V what a ripoff. I might want to burn up 7.5kW :D
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I agree on the 120VDC 30A model for similar reasons. That's much more in the range of a power supply I'd make or use and batteries could easily push past 15A at lower voltages.
Good luck!
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Just playing devils advocate, most all eloads can be paralleled for higher current capability, but not so with putting them in series to get high voltage ratings. So you can extend the 500V eload current mode this way, but its very unlikely you can extend the voltage rating of the 120V eload.
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As one of the contributors to the previous long eload thread (and happy owner of a Maynuo 500V 15A load), I would suggest that everyone is going to have different voltage, current and power requirements, so not sure we can offer any final advice on this topic, other than to make you think widely about your own present and future needs.
I build devices based on nixie tubes WWW.MrNixie.com (http://WWW.MrNixie.com) which need power supplies up to 200V. I am now building an analogue oscilloscope from scratch. That has 300V and 2KV(!) power supplies. ERK.
If you ever get into beefy audio amplifier projects, you will find that they might easily come with +/- 60V DC rails (which will float higher than that, off load), so suddenly an eload rated at "only" 120v will not cut that mustard.
One thing to watch - I was earlier torn between a 30 Amp 150W 300V load, and a 15 Amp 300W 300V version. Which is "best"? Well, if you are measuring a 15V supply, the former 30A rated load can be used up to only 10 Amps (=150W), where the latter 15A rated load can be used up to 15 Amps!! As Dave would say, "Go figure."
Oh - and remember - any load is not "500V AND 15A", but "any combination up to 300W" would be a more accurate description! And 13.8V x 25A is gonna bust the common 300W limit (bigger eloads are available, but price goes up A LOT).
And finally - ouch - if you are going to measure anything on the "hot" (mains) side, I would suggest (1) Don't and (2) make SURE that your eload offers the appropriate isolation/insulation from earth. I would not connect my own instrument to a 340V DC mains-referenced supply :(
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Thank you all for your suggestions/input/advice. I purchased the BK Precision 8500 today; it was on sale, I had a 5% discount code, free shipping and no sales tax collected.
Now begins the pacing while I wait for the delivery guy that I'm sure we all do to some extent. :D
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I concur with LaurenceW's viewpoint, and congratulate you. Could you offer a review of your eload to this thread when you receive it? Dave has done a tear down, but not so much yet on a functional testing; and other viewpoints reveal applications other users haven't focused on.
Thank you all for your suggestions/input/advice. I purchased the BK Precision 8500 today; it was on sale, I had a 5% discount code, free shipping and no sales tax collected.
Now begins the pacing while I wait for the delivery guy that I'm sure we all do to some extent. :D