High DC voltage step down converter

Not entirely sure where to post since I am new to the Forum.

The challenge I am facing is to try and step down High Variable DC voltage to various other smaller DC voltages.

I am using a DC motor (Induction Motor) with brushes which generates high DC Voltage up to 250V DC (maybe even higher than that) depending on the strength of the electromagnet and the rotational speed of the electromagnet.

What I would like to try and do is to tap into that high DC Voltage with a few Step Down Buck Converters. Using multiple of these step down converters will change the voltage of the DC motor which means the step down converter should be able to handle variable DC input voltages, stabilize the DC voltage before producing a stable output DC voltage.

I haven't found any step down DC converters that was capable of handling variable DC input voltages.

Any product / device suggestions would be greatly appreciated.

Regards,
T

This is dodgy stuff - 250v DC is a killer and what you propose doesn’t sound too good and I can’t sensibly advise you to do this project .
There is equipment available to
Do this properly , but ...

Hammy, thanks for the reply and I certainly do appreciate your concern because it is definitely valid. Anything above 48VDC is considered dangerous. However, with the correct precautions one could eliminate most of the associated dangers.

That said, I am unfortunately between a rock and a hard place because slowing the rotational speed of the electromagnet and reducing the strength of the electromagnet will produce a lower output DC voltage. Unfortunately, reducing the speed will also reduce internal cooling which can lead to overheating of the field coils the moment load is applied on the output.

I've been reading papers on Voltage Stabilizers and Regulators....and it would appear that there is not quite consensus on the difference between the two. (What is the difference between a regulator and stabilizer)

I was hoping to find some information on how to stabilize the variable DC voltage and then pass that through a Buck (Step Down) converter to get the required DC voltage.
(Also looking into High Voltage DC-DC converters)

The obvious is to get a more suitably matched generator - depending on your proposed load - a car alternator maybe good for 50 amps at around 14 volts

I haven't found any step down DC converters that was capable of handling variable DC input voltages.

Most of them do handle variable DC input voltages. Many examples.

But starting with 250V is unreasonable.

hammy:
The obvious is to get a more suitably matched generator - depending on your proposed load - a car alternator maybe good for 50 amps at around 14 volts

Thanks for the reply and suggestion.

When bypassing the Voltage Regulator on the alternator, you are able to increase the electromagnet of the rotor far above the regulated output voltage of between 13.0V and 14.7V (give or take a few mV). In an article it is mentioned that an unregulated alternator running at 5000 RPM can produce 150V and its full specified current. (Unregulated alternator output voltage. Post #4).

I came across an IC made by Texas Instruments called the LM5118 with 3Vmin and 75Vmax input voltage and max current of 15A. (LM5118 IC)

Unfortunately I haven’t been able (yet) to source a Buck Boost converter that uses this particular IC…well from China at least.

I am currently using a Nissan Navara YTD25 alternator spec’ed at 12V 50A/130A. If I draw 50A at idle speed (1500 RPM) the stator coils will burn because the internal cooling system is not strong enough, not to mention the voltage drop.

I will continue to see if there is actually a commercially available Buck Boost converter using the LM5118 IC.

jremington:
Most of them do handle variable DC input voltages. Many examples.

But starting with 250V is unreasonable.

Thanks for the reply J.

I agree that 250V is unreasonable if you wish to charge a cellphone or using it for a desktop power supply...nutter comes to mind. However, have you considered the possibilities of having access to 250V DC and 130A ?

Thanks for the link to the Pololu product range of step down converters. I believe it may help me in future... I just need to revisit the drawing board and be less enthusiastic about tapping into 150+V when I can not really harness all that for now.

Regards,
T

However, have you considered the possibilities of having access to 250V DC and 130A ?

Of course, for very heavy machinery.

Nothing at all to do with Arduino, though.

jremington:
Nothing at all to do with Arduino, though.

I am really confused, why not ? I am currently using an ESP8266 (NodeMCU) to control the rotational speed of an alternator rotor as well as the strength of the rotor electromagnet.
In other words, a 24V DC motor has nothing to do with Arduino ?

Arduino as a micro controller is limited to 3.3V, 5V and 12V DC input voltage. It can not produce more than 5V on a GPIO port (depending on the MC you use) and it only allows mA on those same GPIO ports.

There are a fast amount of devices and breakout boards, compatible with Arduino, that require much more than just 5V and a few mA.

I am perfectly fine with someone who wishes to remain within the constrains of 3.3V, 5V and 12V when doing their Arduino projects. However, I deem it unfair for those individuals to decide that anything above 12V DC has nothing to do with Arduino.

No insult intended and none taken.

Regards,
T

Sorry I failed to make that clear. The possibilities associated with 250VDC @ 130A have nothing to do with Arduino.

TinManSA:
The challenge I am facing is to try and step down High Variable DC voltage to various other smaller DC voltages.

For what purpose. To power something, or to measure.

To power: A common universal voltage mains power supply runs internally on (up to ~350volt) DC.
Just connect the 250volt DC to the power prongs (any polarity).
Leo..

J, no need to apologize. I believe I should be the one apologizing.

  • 4x 12VDC 120mm Fans = 48VDC (can’t recall the Amp requirement for those fans)
  • 1x Platinum 22VDC 60A ESC = 22VDC @ 60A (90A for 10sec boost)
  • 5x ESP8266 NodeMCU @ 12VDC each = 60VDC
  • 8x additional 5V VCC = 40VDC (not enough VCC ports on the NodeMCU’s)
  • 2x 12V for rotors = 24VDC
  • 9x 20V charge controllers = 180VDC
  • 1x 12V LED Bar = 12VDC

Total: 386VDC required!! And that is about 70% of the equipment I will be using.

Oh I left out the Orange PI Zero IOT server and various other power hungry devices.

Never did the maths before until now…I think I will need a bigger boat.

In the world I work in, and since I work for myself, I do not have the luxury of a nuclear power plant pushing AC my way during a power outage, no sun to hit my solar panels (because shite goes down at night) and to make things worse I can not use generators because of virtually zero ventilation.

I am honestly not trying to light up a LED with 250VDC.

You have yourself a great evening.

Regards,
T

Wawa:
For what purpose. To power something, or to measure.

To power: A common universal voltage mains power supply runs internally on (up to ~350volt) DC.
Just connect the 250volt DC to the power prongs (any polarity).
Leo…

Wawa, thank you for your reply and being the first to ask for clarity. That I do appreciate.

In my last reply to Jremington, I have listed a few devices I need to power.

Unfortunately I am not able to use mains (power outage), no solar and not generators. However I am able to generate variable high DC voltage.

Can you perhaps explain what you mean with “common universal voltage mains power supply” please.
(If you are saying what I think you mean, correct me if I’m wrong: Use an ATX AC PSU and place the 250VDC on the live and neutral prongs since the PSU uses a 47uF 400V capacitor as a filter ?)

Regards,
T

EDIT: I forgot to mention that I need VDC for both measuring and powering.

Wawa:
For what purpose. To power something, or to measure.

To power: A common universal voltage mains power supply runs internally on (up to ~350volt) DC.
Just connect the 250volt DC to the power prongs (any polarity).
Leo..

I stand to be correct!!

AC/DC power supply with a DC source

Thank you very much for the information Leo! I will most certainly look into your proposal.
Can you perhaps propose a suitable Universal Power Supply that I can use in this case ?

Regards,
T

TinManSA:
Total: 386VDC required!!

This thread is getting weird.
What mains voltage is inside your house (110volt or 240volt).
I hope you didn’t add up all the voltages of your appliances, and ask the provider for 1,000,000volt.

You don’t add voltages, unless it’s the bulbs in a string of Christmas lights.

One 12volt fan needs 12volt, four 12volt fans also need 12volt (not 48volt) and they take the current needed.
You just have to provide a 12volt supply that can at least provide that current requirement.

The same for all the other devices on your list.
Leo…

Your are correct Wawa! My bad!

I should not be doing maths at 01:40AM.

Hi
WHAT!!!

  • 4x 12VDC 120mm Fans = 48VDC (can't recall the Amp requirement for those fans)
  • 1x Platinum 22VDC 60A ESC = 22VDC @ 60A (90A for 10sec boost)
  • 5x ESP8266 NodeMCU @ 12VDC each = 60VDC
  • 8x additional 5V VCC = 40VDC (not enough VCC ports on the NodeMCU's)
  • 2x 12V for rotors = 24VDC
  • 9x 20V charge controllers = 180VDC
  • 1x 12V LED Bar = 12VDC

4 x 12V fans will need a single 12V supply.
5 x ESP8266 will need a sigle 12V supply.
You do not add voltages together when looking at parallel loads.

Why do you want everything in series?

Can you tell us your electronics, programming, arduino, hardware experience?

What are you building?

Tom... :slight_smile:

TinManSA:
Not entirely sure where to post since I am new to the Forum.

The challenge I am facing is to try and step down High Variable DC voltage to various other smaller DC voltages.

I am using a DC motor (Induction Motor) with brushes which generates high DC Voltage up to 250V DC (maybe even higher than that) depending on the strength of the electromagnet and the rotational speed of the electromagnet.

Induction motors are AC only. They don’t have brushes. Perhaps you have a DC generator? Perhaps you can clarify by saying what it actually is (link to datasheet or product page).

What I would like to try and do is to tap into that high DC Voltage with a few Step Down Buck Converters. Using multiple of these step down converters will change the voltage of the DC motor which means the step down converter should be able to handle variable DC input voltages, stabilize the DC voltage before producing a stable output DC voltage.

Many mains SMPS will take DC input (check the datasheet), as the first stage is a bridge rectifier.

I haven’t found any step down DC converters that was capable of handling variable DC input voltages.

Any product / device suggestions would be greatly appreciated.

Regards,
T

Hi Tom,

Programming 15 years, 3 years for the rest.

I know where I went wrong last night.

At the time my mindset was when there is no voltage regulator on an induction motor (alternator), which means that voltage and current will be linear to each other with an increase in strength and rotational speed of the electromagnet. (12V on rotor with an electromagnet rotating at around 6000RPM to 8000RPM can create a voltage of up to 250V+ depending on the alternator used).

I am thinking of using a 2nd alternator on my RV (Old Nissan F23) instead of using my main alternator to charge my (for comfort) batteries.

I know that voltage remains the same in a circuit, but current will change as the load requirements change.
I know that parallel connections require more current.
I understand Ohm's Law.

Where I am at now is to get back to regulating the voltage on the rotor with PWM and external power source up to 12V with feedback (monitoring) on the output voltage (14.7V) to regulate the voltage on the rotor.

I am also considering battery management where batteries are individually charged and monitored.

As the process is tested on a bench I am evaluating the two possible scenarios of regulated and unregulated rotor excitation. However, in my opinion it is really futile to even consider unregulated voltage on the rotor as it just creates so much problems down the line, not to mention dangers associated with high voltage either AC or DC @ 130A.

As Jharington indicated before, maybe this project is not meant for an Arduino forum...

Thanks for your interest Tom, I believe you saw something I overlooked. Wawa (Leo) made the penny dropped for me!!

Regards,
T

Again, an induction motor is not an alternator. Induction motors are about the only motor type(*) that cannot be used as a generator (without complicated active circuitry/control system and an initial power source to bootstrap from, to be precise).

Alternators have a permanent magnet or electromagnet for the rotor, induction motor rotors are just shorted turns of thick metal bar. Current has to be induced in them by the stator, otherwise the rotor is inert.

(*) extra marks for naming the other motor type that's not a generator...