Step up transformer 5000W

[ad78]

i have level 2 charger rated 240V @ 16amp with 3.84KW now who is here using step up transformer?

im planning to get the 5000w. trying to figure or accomplished if it will meet the level 2 that i have @ 240v @ 3.84kw

anyone?

 

[theothertom]

I'm not exactly sure what your question is but doing the math for 5000W and 240V would mean your circuit would pull 20.83 amps.

Edit: If you're trying to step up the voltage to get to 5KW I don't think that will work because the current will go down. i'm not an EE so maybe someone else knows better than I do.

 

[ad78]

I'm not exactly sure what your question is but doing the math for 5000W and 240V would mean your circuit would pull 20.83 amps.

Edit: If you're trying to step up the voltage to get to 5KW I don't think that will work because the current will go down. i'm not an EE so maybe someone else knows better than I do.

im just trying to be safe that is why im looking for a step up with higher KW vs the default level 2 Charger. im pretty sure the specs of the transformer im looking will accomodate the level 2 charger. it is just im looking who has one and the experience.

i guess im the first one who will try this. i'll keep you posted.

 

[jadnashuanh]

The charging circuit is IN the car...an EVSE is just a fancy on/off switch. Its internal components may not handle higher current, and the car will not appreciate higher voltages! FWIW, the EVSE sends out a signal to the car announcing how much current it can provide, then the car decides how much it will use, up to, but not more than the EVSE says it has.

I do not see how the use of a transformer would help make this work...you need a different EVSE and probably upgraded wiring to it to supply more power to the car. If you are from an area where the 7.4Kw onboard charging is optional, nothing you can do externally will increase the charging rate.

 

[ad78]

Isnt that the EVSE sends the signal in the car? If so, the one i have is 240v rated @ 16A, 3.84kW

Now the transformer rated @ 240v 5kW can handle the EVSE needs.. this will lessen my time vs level 1 cable that came with bmw

 

[jadnashuanh]

With very few exceptions, the EVSE's pilot signal (the one that announces how much power is available to the car) is NOT a user adjustable item. On those where this signal is adjustable, it can only be adjusted LOWER than the maximum, never higher. You might want to do that if you couldn't plug it into a plug capable of supplying the maximum available. In no case is a transformer going to help. If you have a 120vac EVSE, most will not work if you plugged them into a 240vac circuit (you might achieve with a step-up transformer). Doubling the voltage would theoretically double your power at the same amperage. Finding that large of a step-up transformer would be expensive, and buying a new EVSE may be cheaper. Plus, your circuit breaker and wiring would then also need to be doubled in size, so rewiring for 240vac would likely work better. FWIW, there aren't any 120vac 30A plugs or receptacles that I'm aware of...they max out at 20A.

 

[ad78]

I have a separate EVSE.. i dint plan to use the 120v on the transformer.

Like i said, my EVSE is 240v 16A @ 3.84kw (3800W)

The transformer im going to buy is step up 240v @ 5kw (5000W)

My garage plug is 120v 20A

 

[jadnashuanh]

Okay...those things are not cheap...it would probably be cheaper to rewire or add a 240vac circuit. If you put 20A in and bump the voltage up to 240vac you're still limited to 20*120 watts (2400), and the car would try to take 20A @ the 240vac, (4800W) which is expecting 40A input at 120vac...it won't work!

A 20A circuit at 120vac is limited to 2400w max, regardless of what you do. You can't manufacture additional power with a transformer. The signal out of the EVSE announces how many amps, and that will exceed the capacity of a 120vac 20A circuit...you'll trip the breaker.

 

[ad78]

But the EVSE is rated only @ 16A 240v from there my circuit breaker is sufficient at 20A

 

[I33t]

I have a separate EVSE.. i dint plan to use the 120v on the transformer.

Like i said, my EVSE is 240v 16A @ 3.84kw (3800W)

The transformer im going to buy is step up 240v @ 5kw (5000W)

My garage plug is 120v 20A

What is the rating of the power cable you will plug the transformer into?

A transformer will increase the voltage, sure. But... increasing the voltage will reduce the amps. So plug your tranny into 120v 20A and it will output 240v 10A.

Info from tafe nsw: https://sielearning.tafensw.edu.au/toolboxes/Electrotechnology/toolbox/hq/mag1/transfrm.htm

Once you have worked out the voltage or number of turns in a secondary winding you can also work out the current that is being induced too.

The ratio of current through the windings can be expressed as follows:

Gaphic of equation

Where:

Vs = Voltage induced in the secondary winding (in Volts)
Vp = Voltage applied to the primary winding (in Volts)
Ns = Number of turns on the secondary winding
Np = Number of turns on the primary winding
Ip = Current in the primary winding
Is = Current in the secondary winding

Therefore, if the voltage ratio is 2:1, then the current ratio is 1:2. If this ratio is applied to the step down transformer with a current flow in the primary of 2.4 amps, then the amount of current flowing in the secondary would equal 4.8 amps.

 

[brastic]

The short answer is no, you cannot do this.

You cannot take a 120v 20A circuit and magically make a 240v 20A output. Everything that l33t stated is true. You will need to get an electrician out and safely and legally put in a 240v circuit to support the EVSE. I would highly recommend to have a 240v 40A circuit breaker put in. This way in the future you can step up to a L2 32A charger.

 

[jadnashuanh]

Power=volts*amps . You can't make more power by simply raising the voltage - the max you have is the 120vac*20A...or 240vac*10A, both are the same amount of power that that circuit can provide. Using a transformer, you'd be asking the 120vac circuit to supply more power than it can, and the EVSE would be announcing to the car that that additional was available, and so would overload the circuit. If you could adjust the EVSE to announce (via its pilot signal) that it only had 10A available (well, 8A to follow the 80% rule), it would then be supplying exactly the same amount of watts since you'd doubled the volts, you'd have to halve the power to make the same power on the inlet as the outlet. Then, you'd lose some efficiency to heat in the transformer, even when it was idling with nothing running on the outlet.

Put in a dedicated 240vac circuit...the bigger, the better, up to a point...the wiring is not inexpensive, and bigger wire costs more. In my panel, I could only manage a 40A circuit (limiting me to a 32A EVSE), since I needed the rest of the capacity for other electrical things. It would have been VERY expensive for me to upgrade my service since I'm in the middle of a row of townhouses, and would have needed access to 5 other units to run new supply wire to my panel...not going to happen!

 

[ad78]

another consideration is the Quick 220. downside is you plug in into two different socket.

 

[brastic]

another consideration is the Quick 220. downside is you plug in into two different socket.

I was going to respond to this post, but will let jadnashuanh do that.

On another note, have you thought about how to make a home made 480v DC charger for homes? I am thinking that you could find a way to make this happen.

 

[jadnashuanh]

It can be somewhat difficult to find two 120vac receptacles on opposite legs of the incoming power to achieve 240vac. The use of extension cords is not recommended, either. Usually, in one room, all of the receptacles are on the same leg, and just plugging into two different ones won't achieve the desired results. Then, if there's any fault in the device, it can create a hazardous situation. It can work if everything's working properly. IMHO, too risky for the benefit.

If your power panel is not far away, it's pretty inexpensive to wire up what's needed to use the level 2 device you have. Even though it is 16A (if I remember correctly), it will be more than twice as fast as the included 12A, 120vac device that comes with the car (some have indicated that the latest version is 10A, 120vac). Remember, power=volts*amps, so doubling the voltage with the same number of amps, doubles the available power. Since power is what the circuit breaker is measuring, that's why you can't just use a transformer to raise the voltage...the device you have will tell the car it can draw 16A, which is double what the 120vac circuit can handle.

 

[gt1]

I have a separate EVSE.. i dint plan to use the 120v on the transformer.

Like i said, my EVSE is 240v 16A @ 3.84kw (3800W)

The transformer im going to buy is step up 240v @ 5kw (5000W)

My garage plug is 120v 20A

I hate when people respond with "call a pro" on a technical question, but this is just the case when it is justified. You don't know electricity and literally playing with fire.

 

[ad78]

I have a separate EVSE.. i dint plan to use the 120v on the transformer.

Like i said, my EVSE is 240v 16A @ 3.84kw (3800W)

The transformer im going to buy is step up 240v @ 5kw (5000W)

My garage plug is 120v 20A

I hate when people respond with "call a pro" on a technical question, but this is just the case when it is justified. You don't know electricity and literally playing with fire.

so what's your point? that is why i posted because i dont have any experience with step up transformer.

 

[gt1]

My point was that you were over your head with this project. Dealing with a multi KW circuit is not the best way to learn.

 

[ad78]

My point was that you were over your head with this project. Dealing with a multi KW circuit is not the best way to learn.

Why bother posting when you cannot even put a simple technical input here?

 

[jadnashuanh]

Bottom line...16A at 240vac that you might get out of a transformer requires 32A coming in at 120vac (plus whatever may have been lost in wasted heat). You can't get 32A from a typical 120vac circuit. IOW, it won't work. The EVSE tells the car how many amps it can draw, not how many watts. While the car won't 'pull' more than about 7400W, it looks to the EVSE to be accurate of it's amperage capability (circuit breakers are based on amps, not wattage, as are the power ratings of components including wiring).