Hello all,,,, i have recently purchased a 1kw induction heater, but i do not have a sufficient power supply to drive it, my highest power supply adapter is 24V4Amp(~100W). and the induction heater is 350W minimum. So i decided to make my own and its been a long time coming. ...
Now i am here to ask how can i make the output a variable amp and variable voltage output, i wanted to do it with a potentiometer voltage divider, like one can do with a motor, but i do not think my potentiometers can run 25-30 amps., so i want to ask how can i make the output variable, high power MOSFETS? or do i add more windings to the transformer and and just get a variable switch? but i do not want to do that unless i really have to.
Please advice me with examples and explanations. Please.

 

What is the power supply specification that the induction heater requires?

 

Why do you want a variable current PSU?
Use a power MOSFET with PWM control on the gate.

 

What is the power supply specification that the induction heater requires?

The induction heater is 350minimum at 24Vminimum, and 900w max at 36volts max..... so there should be about 11-15amp output at variable 24-26 volts

 

Why do you want a variable current PSU?
Use a power MOSFET with PWM control on the gate.

may i ask how to do that, the pwm i can do with a 555timer, but how will i connect that to the power mosvets to regulate voltage. please give a diagram

 

it has also been suggested to take away the current limiting capacitor at the mains side and connect the transformer clean to mains and fuse and then make things safe on the output side, ass the capacitor apparently drops the voltage as i connect a load.... is this advised? i'm afraid of the thing drawing too much power from the mains that is why i added the current limiting capacitor in the first place, is the capacitor needed or safe too use or not?

 

If this is for an induction heater, why do you need to regulate the voltage?
With a variable resistor you can control the PWM from 0% to 100%. The power output is linear with the PWM duty cycle.

 

You can also try a light dimmer.

 

Definitely eliminate that "current limiting" capacitor.
Not needed and not much current drain through the primary until a load is connected.

 

A resistive heater will respond linearly to PWM. An induction heater will not. I would supply a constant voltage of between 24 and 36, as the specification says. There is no telling what would happen with PWM.

 

A resistive heater will respond linearly to PWM. An induction heater will not. I would supply a constant voltage of between 24 and 36, as the specification says. There is no telling what would happen with PWM.

It will have some sort of electronic power supply of its own, and switching it on and off thousands of times a second is a sure way to break it.

 

The induction heater is 350minimum at 24Vminimum, and 900w max at 36volts max..... so there should be about 11-15amp output at variable 24-26 volts

Does it not have any way to control the power apart from varying the voltage?
I would recommend a variac.

 

Definitely eliminate that "current limiting" capacitor.
Not needed and not much current drain through the primary until a load is connected.

I second that i added it to the simulation, and i saw its more stable. i have seen ELECTROBOOM on you tubes ZVS circuit(i wanna build my own too) and saw that yes the whole system is actually minimal power until there is a true load.

 

If this is for an induction heater, why do you need to regulate the voltage?
With a variable resistor you can control the PWM from 0% to 100%. The power output is linear with the PWM duty cycle.

the VARIABILITY comes in with future applications. if i make this high enough power maybe i can then later CHOOSE to only harden steel(im a knife maker hobbiest) at 500w-1000w or actually melt metals like aluminum and copper at about 2000w....so the variability is for future applications.... choosing what i need at the moment.....

the duty cycle is a helpful tip thank you.

 

Does it not have any way to control the power apart from varying the voltage?
I would recommend a variac.

i'm trying to build the PS from scratch but since its my first AC circuit built i thought of taking it to the masters and learn from them
... unfortunately the induction heater of 350w-900w did not come with PS....look if i MUST buy a variable power supply i will.... but i thought experience gaining and future preference will dictate me to at least TRY and make one myself first

 

It will have some sort of electronic power supply of its own, and switching it on and off thousands of times a second is a sure way to break it.

the best i can tell and its pretty damn obvious the induction heater is a finely tuned(modified)(there are parts there that shouldnt be but i guess its for the fan) a ZVS circuit with the main coil being the heating one..... so there are already power MOS or POWER TRANS in there... i am FULLY willing to only supply what it needs, but as i said in another reply the variability is for the future, maybe i nee something that need less power in my "future ZVS circuit" for reasons i dnt know. but iaf at all possible i would like to make it variable in power output. even if i must buy components....

 

Does it not have any way to control the power apart from varying the voltage?
I would recommend a variac.

it literally just says that on the input side...24v to 36v....then under it 350w to 900w.... its almost JUST only the ZVS circuit as the induction heater.

 

It will have some sort of electronic power supply of its own, and switching it on and off thousands of times a second is a sure way to break it.

you may have a point there

 

"unfortunately the induction heater of 350w-900w did not come with PS.." So we have no understanding of EXACTLY WHAT the TS actually does have. WE do have another statement: " The induction heater is 350minimum at 24Vminimum, and 900w max at 36volts max..... so there should be about 11-15amp output at variable 24-26 volts" So evidently there is an oscillator circuit of some type that requires a DC supply. So what is required is a transformer for the local mains voltage input and a 28 volt output at up to 15 amps. That could be a surplus industrial transformer, even. Find a used industrial controls transformer, 480 volts to 120 volts, rated one KVA. Then feed the 120 volt mains into the 480 volt side and get 30 volts out Then the suitably rated bridge rectifier and the TS has the DC supply. The drop in the bridge diodes will bring it down to 28 volts. NO NEED TO FILTER THE DC!! The input current can be as much as 10+ amps, so use a high current SSR. The heat input is controlled by the ON time, as I recall.

Induction heating for metal hardening is seldom gentle, so a simple "ON" timer calibrated in seconds is all that is needed.

BUT if this is an induction heater for cooking, that is a different problem. My guess was induction heating for metal hardening.

 

One source of a mains transformer is a scrapped microwave transformer, you need to remove the secondary and wind on the new one with suitable gauge enameled wire.
Typically around 4 turns/volt.
Also punch out the magnetic shunt, if it has one..