AC to DC Converter Question.
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  1. #1
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    Default AC to DC Converter Question.

    I have built a conveyor system per the customers prints which required it to be 'universally powered' anywhere in the world. The customer stipulated 12 DC motor, controls and batteries/charger.

    This is a prototype...so the logic has changed midstream..now they would like a 120v AC option.

    All the controls are in as well as the DC gear motor. The motor is a 12 volt DC motor rated at 900 watts, 1.2hp and full load current of 85 amps.


    I want to stick some type of converter on the conveyor that I can plug into a 120 volt circuit, then into the existing DC stuff...and Bob's your uncle.

    I found this. Amazon.com: AmpFlow SCN-1000-12 1000W, 80A, 12V DC Parallelable Power Supply : Electronics Am I kidding myself or would something like this work?

    What am I missing here!

    Stuart

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    Your simplest and most reliable bet will be a transformer-rectifier power supply. The motor is an inductive load, so a filter cap and v-reg would not even be necessary as long as the controls will operate on unfiltered DC.

    Off-the-shelf DC-DC converters can be a crap shoot in terms of reliability. I would steer well clear of anything from Amazon, E-Bay or similar places infested with low quality Chinese no-brand products. And besides that, the law of MBTF dictates that as part counts go up, life expectancy and reliability go down. DC-DC converters contain a *lot* of complicated semiconductors.

    If this is just a one-off project, you can E-Bay a used 1.5kVA, 12V control transformer and source a 100A single phase rectifier. Note that rectifiers that size will require either a substantial heat sink and/or forced air.

    If the DC does need to be filtered on the other hand, then you'll need to use an 8.5V transformer instead. Peak voltage (nominal filtered DC voltage) = RMS voltage (AC voltage) * sqrt(2). A 12VAC transformer would yield 17VDC or thereabouts if filter caps were to be connected.


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    Thank you. The DC motor is battery powered..but, is controlled through a DC motor controller that has soft start and stop as well as OC protection, E-stop and a bunch of other stuff. It's straight from China, but I've used them before and they seem to be durable and made well.

    I'm going to guess that the controller is going to want pretty clean DC voltage, but I'm out of my comfort zone on stuff like this.

    Stuart

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    I know nothing at all about that company. they could be good, or a maker of cheap imitations, I do not know. And I have never had one of their products.

    That said, the unit does cover most of the world. It lacks 100V capability (per specs), but covers most of the rest of the world. So that is a plus.

    If it is a good quality unit, it could work fine if it will power that motor. I cannot give any opinion on the quality, I just do not know.

    The transformer and rectifier supply option will be quite reliable, but needs a transformer with multiple taps for 100/120/230/240 voltages in order to cover the world voltage requirement (which I assume is still in place).

    If the product will stand the added price, a power supply like the one you show would likely work fine. The DC controller should work somewhat like a VFD, probably having a soft start that will limit the turn-on surge as the motor starts.

    You probably will want to check the current draw of the motor, vs the 80A capability of one of the units. You should have at least 25% more capability than the motor needs. I am basing that on having a controller. If you needed to start the motor straight across the 12V supply, I'd suggest a considerably larger supply unit to handle the inrush, or at least one with a large short-term surge rating.

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    I would look at a universal switching power supply that pretty much could be used anywhere and you would not need to certify for other countries. There are a number of mainstream switching power supply companies, I have been using Mean Well power supplies for a number of years and have been very reliable. A wide range of versions, but these are all around $200-230 and have a universal input as well as protection circuits and if required PFC. These models should be available world wide.

    Most of these have a higher overload capacity, but there is derating based on input voltage. It also would depending on the loading of the system, if there is a soft start or current controller. etc. Above 1 kW output probably need to be at 200V and over.

    MEAN WELL SE-1000-12 Switching Power Supplies 999.6W 12V 83.3A
    https://www.mouser.com/ProductDetail...at8YsVyIHZ4%3D

    MEAN WELL PSPA-1000-12 Switching Power Supplies 960W 12V 80A W/PFC and Parallel
    https://www.mouser.com/ProductDetail...9PqGgalw%3D%3D

    MEAN WELL HRPG-1000-12 Switching Power Supplies 960W 12V 80A W/PFC
    https://www.mouser.com/ProductDetail...1KZDY8Cw%3D%3D

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    Quote Originally Posted by mksj View Post
    ...................I have been using Mean Well power supplies for a number of years and have been very reliable. .......................
    Interesting.

    We had a low volume product that we used a Mean Well supply in. That model, at least, kept failing for no particular reason. We put the same rating from a different company in place of the Mean Well, and never had another one fail.

    So they have a rotten reputation as far as we were concerned. Seemed as if the supply was very marginal, barely did what it promised.

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    I acquired two of these battery chargers, one had blown up.

    Low-noise, high-power 12V battery chargers (adjustable 13.8 VDC, 15 to 90 amps) with 2 year warranty

    I have 2 of the 45 amp versions. build quality is good, but the battery chargers are not sealed in any way, I would not want dust or debris anywhere near them. put them in a box with a fine screen or filter for the air inlet.

    Circuitry is pretty simple, they are forward converters utilizing a UC3844 up to 50% duty cycle, with a big output inductor and minimal capacitance. They are constant current (max voltage adjustable but nominally set for 13.6-13.8) but I don't know the lower voltage at which they will turn on. I assume they are designed to charge a 12v battery at the full current, but if say the output voltage is at 2 volts, i don't know what current it will send out. I do know however that a standard 12v power supply may trip and not turn on, if it is used to charge a 12v "dead" battery at say <9v initial voltage.

    I actually successfully repaired one of them, but then blew it up again because I was directly driving the main mosfet from the output of a uc 3842 (was too lazy to rebuild the blown up npn/pnp transtor buffer), and i increased the load until the mosfet shorted out and blew up.

    anyhow i highly doubt you need a 90amp power supply for your application if the 12v battery is maintained as a buffer given the non continuous nature of a battery powered ... conveyer belt?

    and would definitely suggest a PFC input, universal 100-267 vac input battery charger so it can be used anywhere without some idiot plugging it into a 220v circuit when the switch on the back is set for 110. i can't find any cheap good ones though.

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    Worth a reminder even though I'm sure you're aware that motor inrush is a significant consideration. Soft-starting the motor via your existing speed controller will be imperative if using any sort of switching power supply. Switching power supplies won't handle the 600~1000% FLA locked rotor current that a DC motor will demand when started directly across the line, unlike a much 'chunkier' power supply like a transformer or battery would. Wafer-thin transistor junctions and tinned circuit board traces simply don't have the thermal mass that lead plates, copper windings and steel lamina do. Resistive heating = I^2R.

    If going the SMPS route, I've heard Lambda is a trusted brand.

    Mouser.com

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    You stated " BATTERY"...

    Look for good quality battery of AGM type that can run everything for a few minutes minimum.

    Meet get a battery charging power supply that will properly FLOAT the battery as well as power the motor.

    All of these are common off the shelf items and with international sales most are universal input, 100 to 250 volt input with only difference being the power cord that is interchangeable having the correct plug.


    BONUS POINTS...

    Client wants it to go anywhere...

    If it can run on battery and has a battery as PRIMARY POWER then it truly can go anywhere, no primary power, no problem, bigger battery and solar panel.
    Sent from my SM-G781V using Tapatalk

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    Quote Originally Posted by Tony Quiring View Post
    You stated " BATTERY"...

    Look for good quality battery of AGM type that can run everything for a few minutes minimum.

    Meet get a battery charging power supply that will properly FLOAT the battery as well as power the motor.

    All of these are common off the shelf items and with international sales most are universal input, 100 to 250 volt input with only difference being the power cord that is interchangeable having the correct plug.


    BONUS POINTS...

    Client wants it to go anywhere...

    If it can run on battery and has a battery as PRIMARY POWER then it truly can go anywhere, no primary power, no problem, bigger battery and solar panel.
    Sent from my SM-G781V using Tapatalk
    The current system uses a 12 v, 100AH AGM battery that will power the conveyor through its required 120 short on-off cycles which last about 15 seconds. There is a smart charger for the battery, but its only a 5 output.

    Are you saying, leave the intact DC system there, powered by the battery, and merely keep the battery charge up with a charger attached to the 120v supply?

    Stuart

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    An N=1 with one model is not representative of a product group or a manufacturer's products. Mean Well builds a wide range of models, so the cheaper ones are just that. Have installed 100's of their power supplies and not had any failures in the last 10 years. If you want to pay 2-3X the price, there are better ones out there.

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    Quote Originally Posted by mksj View Post
    An N=1 with one model is not representative of a product group or a manufacturer's products. Mean Well builds a wide range of models, so the cheaper ones are just that. Have installed 100's of their power supplies and not had any failures in the last 10 years. If you want to pay 2-3X the price, there are better ones out there.

    It was N= 3 or 4 with that particular product..... Of course the other products are just that, different. Maybe better. Maybe the same.

    I've NEVER accepted the "cheaper means it fails" concept. To me, "cheaper" means it lacks things the more expensive ones have, but that it works fine and is "good within it's category". Temperature range will be limited, there won't be as much (or any?) larger short term current rating (it just shuts down if excess current is drawn), that sort of thing.

    That should never mean you ought to expect it to fail.

    When several cheaper products from a manufacturer fail without the user exceeding published limits, that's on the maker, who it is fair to assume accepts a "failure to meet spec" with some of their products. There is a basic QC problem with the company if that is the way they operate.

    "Cheaper means it fails" is BS that has been foisted on us by cheap import products.

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    I guess we agree to disagree in these times. Manufactures build all different levels of equipment based on cost/market/specifications/durability/etc. Many products are poorly designed, often minimize cost down to the pennies and have a different expectations as to performance/durability. In this case the comparison to to a generic brand sold on Amazon, which would be the last place I would shop for these type of products. If I buy a Chinese mill or lathe at 1/10 the price of a domestic or EU machine, I do not expect it to be as durable. I have had my share of bad models and duds from some manufactures while other models have worked just fine. Granted I do not have the range of experience of most people here, but have built/installed hundreds of system and have my preferred products that through the years have been durable for me. Your experience is different, and your budgets richer. Products that fail or are poorly made I no longer use. In years past people took pride in designing equipment that would last years/decades, these days it seems everything breaks or is designed to fail over a much shorter time. I guess that is why Mean well warranties some of there less expensive products for 1 year while others are 7 years.

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    Well...this thread seemed to get derailed by folks arguing about the durability of various electronic components, so I'm not 100% sure that my question was answered. I do appreciate some of the recommendations, and hope I understand all the mumbo-jumbo, not being an EE.

    So if anyone has any clarifying statements, I'd love to hear them.

    Stuart

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    Quote Originally Posted by atomarc View Post
    Well...this thread seemed to get derailed by folks arguing about the durability of various electronic components, so I'm not 100% sure that my question was answered. I do appreciate some of the recommendations, and hope I understand all the mumbo-jumbo, not being an EE.

    So if anyone has any clarifying statements, I'd love to hear them.

    Stuart
    *yawn* You want to JF buy s**t that already works. Not "invent" the industry.

    So long as... the BATTERY is the key.. and all the controls are load side of the battery ...and use is predictably infrequent?

    The real concern is largely that a "float" / recovery always-ON charger supply will not damage the battery from OVERCHARGE.

    Which happens to be a bigger "permanent" killer of secondary cells than draining (temporary) them is.

    Marine & standby gen-set industry should have what you want, right off the shelf.

    Ranking The Best Marine Battery Chargers On The Market

    Now... if the battery is just a "buffer" for smoothing, and the power supply has to carry the WORKING load?

    Dif'rent story.

    Presence OF a battery, load-side circuit, actually makes it HARDER and more costly, not cheaper and easier, to use anything BUT Brute Force & Bloody Ignorance types of supply. Or MORE sophisticated and sensored-up,, not just blind ones.

    IOW, it's kinda bass-ackwards.

    See also "UPS" and Solar industry goods, suppliers, and concepts.

    "Making" is cheap as sin. TESTING ... and liability for fail ... is the Royal B**ch Kitty.

    Buy it. With recognized certs. Agreed with the customer.

    Put that (reputable) maker's Warranty in the line of fire. It's what they are paid for.

    Not your own modestly-funded ass.

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    Quote Originally Posted by atomarc View Post
    The current system uses a 12 v, 100AH AGM battery that will power the conveyor through its required 120 short on-off cycles which last about 15 seconds. There is a smart charger for the battery, but its only a 5 output.

    Are you saying, leave the intact DC system there, powered by the battery, and merely keep the battery charge up with a charger attached to the 120v supply?

    Stuart
    Yes.

    That is how Telcom switches have been done for many years

    Power plant is "float service" meaning it maintains the batteries at full charge while supplying power for the load.

    Is power is lost the battery is used with no switching.

    "N+1" is a design parameter, "need plus 1" to set your build level.

    If you need 1 battery you add one so you have spare on line.

    If the load is 5 amps then you consider battery charging if needed and select a power supply that meets this need but not way over size.

    You then get another supply to meet the N+1 rule.

    Slightly cheaper units maybe but you need to be able to determine when one fails.

    Easy to do with a couple diodes or other tricks.

    The key is to pay the price for battery charging power supplies as they are designed for the high rush current from a low battery.

    Sent from my SM-G781V using Tapatalk


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