I have 48volts dc and want to keep 48volts but I want to control the amps. How?

Answer 1

What exactly are you trying to do?

You're getting some weird answers here.

A fuse doesn't "control" current, it just creates a circuit that breaks if the current goes over some amount. Not a very good solution. :/ (you may want to also have a fuse though to protect your load once you do something else to control the current)

An Isolation transformer may be a good idea if you had 48 VAC, but it won't do you any good in a DC circuit. (they block DC)

Constant current regulators are for conditions in which a constant current is more important that a constant voltage, since you meantion a specific voltage, but not a specific current I assume that you just want to keep your current under some amout while keeping 48 VDC as you said. Current Regulators often adjust the voltage as the way they keep the current constant.

For a simple DC circuit you could use electrical ballast. (just add a resistor) but if it was in series the voltage drop across the resistor would put you below your 48 volts.

If your supply is 48 VDC your current is going to depend on your load one way or another. Many devices (like some old servos) will draw so much curent that they will destroy themselves if you aren't careful.

A solution I like is pulse witdh modulation, or in other words, to very rapidly switch the voltage on and off (apply a square wave) you can choose what % of the time the voltage is on vs. off (duty cycle) such that the average power meets your needs.

You can do this with a couple of 555 timer circuits to control the timing of a power transistor. See this link for an example of this with a DC motor. http://www.dprg.org/tutorials/2005-11a/index.html

Answer 2

It would be good to know what kind of constant current you are talking about needing.
Is it a matter of milliamps or amps or 50 or 100 amps?
Also - how smooth a voltage do you need?
If very smooth DC is required, forget these exotic pulse width modulated pass transistors and peripheral circuitry answers..

Any answer for this requires more info, but none yet have really asked any specifics, and none provided.

If your load is varying but requires constant 48 volts, along with a constant amperage flow, -- you would need a power source capable of maintaining a regulated voltage of 48 volts, along with being sufficiently stout enough to source enough current in worst case scenario, in your variable control of amperage. I can only presume you wish to adjust current flow for more than one application?

I can wonder if this is for charging a battery?
Supplying an audio circuit?
Scientific research?
Metal Plating?
Welding?

All of these will have widely differing costs of acquiring the appropriate equipment....

Can't help much more at this point.....

Answer 3

Since it is DC, a transformer won't work. You will have to pulse the output so the maximum voltage remains 48 but the average drops to supply the amps you want.

Answer 4

You'll need a constant current regulator. Circuits for these devices are fairly common. A google search for constant current regulators should get you what you need. You'll find that a constant current regulator is fairly easy to build, once you know how.

Answer 5

Get a constant voltage transformer/rectifier. Or get a constant voltage/constant current unit and set the output volts to 48v, then vary the current as you require using the current setting

Answer 6

you would be able to desire to furnish WHAT sort of RECTIFIER CIRCUIT ( OR CONVERTER ) replaced into USED FIRST.........examples.. [a million] hassle-free much less costly make 0.5 wave has approximately decrease than 50% performance. [2] hassle-free finished wave has approximately decrease than 80% performance. [3] including greater regulating circuit gadget has decrease than 70% performance. [4] Very previous way utilising motor to tug a 48V DC generator has decrease than 60% performance. [5] costly switching mode has approximately no greater effective than ninety% performance.

Answer 7

Control the load resistance. Or, if the load is fixed and cannot be varied, you'll need a constant current regulator.

HTH ☺

Doug

Answer 8

Isolation transformer. Or a ballast circuit.