## Splitting loads among step-up transformers

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Hi all,

I was curious if there was a way to split amps among step-up transformers. What I mean by this is that, for example, let's say I have a input of 20V 40Ah and two transformers that can ramp up the voltage to 40. Only problem is that the transformers have a constant intake limit of 20 amps per transformer. Is there any way to divert the amps going to each transformer so that each transformer is supplied with 20V 20Ah? If that is achievable, could I simply wire the ends of the transformers together to combine the total amps or will that result in system failure?

Thank you.

This post raises so many questions!

First is: what is your power source? Normally, the term AmpHr is used only for batteries. Battery implies DC. Transformers do not work with DC. So, maybe we have some crossed wires or misunderstandings, here.

Second is: Do you know what controls the power through a transformer? Answer: It is determined by the load. If you have two otherwise identical transformers and one has a 5W load and the other has a 10W load, the first will take 5W from the source and the second will take 10W from the source. Power ratings of transformers only give the upper limit of the amount of power a transformer can handle. For example a 100W transformer that has a load that takes 20W will only take 20W from the power source.

Third question: What do you mean by: A transformer is supplied with 20V 20AHr? Do you mean that the power source provides 20V? Where does the 20AHr number come from? Transformers are not supplied by so many AHr. Transformers are not even supplied by so many Amps! Transformers will DRAW a certain number of Amps if the load demands it.

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

Last Edited: Tue. Jul 2, 2019 - 12:40 AM

Is this what you are looking for (combine 2 transformers to allow higher power loads)?

https://www.hvacrschool.com/conn...

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

Hey Jim,

Sorry for all the confusion, I'm somewhat new to the workings of electricity and its many components. As for more information of my project, I'm trying to build an electric minibike, but need more information about how to feed the right amount of power to my motor.

The motor controller (if you wanted a look at it):  https://www.aliexpress.com/item/32927410741.html?spm=a2g0o.detail.0.0.744864d8o4OHO7

So far, I can put 6 batteries into a certain configuration (4 series, 2 parallel), giving me 30.4V and 131Ah. The only issue is, the motor runs at 60V. I was hoping I could use something like the step-up module earlier to meet the demands of my motor, which is 60V 16.6 Ah/h. Can it be done? Even then, would it only be able to run just under 4 hours?

Last Edited: Thu. Jul 4, 2019 - 05:55 PM

Not what I was looking for, but useful knowledge nonetheless. Thanks!

Transformers work only with AC; they "sort of work" with pulsating DC (which is what you get out of typical motor speed controllers) but not reliably; they do not work with plain DC.

So, for your application, I do not think that a transformer is the solution you need. In fact, I, personally, would not even try. Much better to use a motor that fits your battery, or a battery that fits your motor.

With that out of the way, lets get some basics under control.

When used for traction (eg, car, truck, scooter, bike, etc), getting the vehicle from one place to another takes a certain amount of ENERGY. It takes energy to overcome friction and to go up hills. You CAN (if your system is built to do so) get energy back going down hill. POWER is a measure of how fast ENERGY is used. For example, going up a certain hill at 10 miles per hour takes twice as much power as going up the same hill at 5 miles per hour, even though the same energy is involved in both cases (twice the speed takes half as long).

Batteries can be characterized by the amount of energy they hold. Volts X AmpHours is one way to measure energy. Power is Volts X Amps. Theoretically, 5 batteries in series hold the same energy as when they are connected in parallel. The difference is that for a given power output, the series connection takes less current (Amps) because the voltage is higher. Parallel connection requires more current because the voltage is lower. Volts X Amps!

When you say that a motor is rated for a certain power, that is the power that it can output continuously (unless it is an intermittent power rating). In part, this is governed by its ability to get rid of waste heat. It is also governed by the size of the wires and the amount of iron in the rotating part and the fixed part. When you drive a motor with a particular voltage, it is the current that varies according to the load. More load, more current. So, if you have a motor that is rated for a certain number of kW or horsepower, it will consume less electrical power when it is lightly loaded (e.g. cruising on the flat) and more when it is more heavily loaded (going up a hill). But, in all likelihood, it will NOT consume the rated power unless it is a motor that is too small for the application. Thus, YOU have to choose a motor with the correct power rating for the application. Make it too small, and will overheat when going up a hill (or, maybe, even on the flat). Too big, and the motor will be large, heavy, and expensive (and waste more power than it should at light loads).

Motors are strange beasts. At a given voltage, a motor can do a certain amount of work and draws a corresponding current. If you INCREASE the voltage, the RPM will increase and it is possible to do more work. The current will also go up. So, two factors control the current that a motor draws: the voltage that is used to power the motor and the amount of work (load) that the motor is required to do. Typically, smaller DC industrial motors have graphs with sets of curves that show the current at different supply voltages and at different loads. Hobby motors often do not have such information.

So, my strong recommendation is to match the battery voltage more closely to the motor, or visa versa. You will have something that works MUCH better. Also, even if you could find transformers to do what you request, at that power level, they are costly, heavy, and big.

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

Last Edited: Thu. Jul 4, 2019 - 07:04 PM

Why are you talking about a transformer since they only work with AC?

Where are you using AC in your system, maybe the motor driver?

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

I believe what the OP is talking about is a DC-DC convertor (and by following the link, I concur) also known (misleadingly) as a "DC Transformer".

They are not transformers.  And no, they don't 'share' worth a damn.  Two in parallel will fight each other until one explodes, leaving the other to haul the whole load until it too explodes.  Not a good plan at all.

Analog transformers (those giant bricks of layered iron and wrapped copper wire) do share AC loads fairly well.  S.

The transformers referenced in the three links are AC power transformers. They DO NOT work with DC, steady or pulsating.

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

Really?  This is what I got:

1200w high power dc-dc converter boost step-up power supply module

While 'pulsating' DC as a square wave could be considered AC - It's a sine wave, really, just with all the 3rd harmonics added in - I generally concur with your remarks.  I have suffered badly with mismatched motors in the past, and would prefer not to do so again.  S.

Really?  This is what I got:

I think Jim was referring to the 3 links I posted, referring to REAL transformers...the original question was rather poor

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

Oooops, I looked at avrcandy's post and mis-read it as a post by the OP.

That is quite a "step-up" module. Didn't know that they exist! If that module produces up to 80V, I don't see what the problem is with the proposed motor. Motor is max 1Kw, module is rated to 1.2Kw. Ought to work.

The problem I see is controlling the step up module output voltage. It is clear that it is adjustable, but not clear if that can be done remotely (e.g. a handlebar speed control, or such).

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

Last Edited: Thu. Jul 4, 2019 - 08:40 PM