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Robert2

Sat May 10 2014, 12:21PM

Registered Member #1773 Joined: Tue Oct 21 2008, 06:56PM
Location: Poland
Posts: 93

Hi everyone!

I recently started a project induction heater.
The driver is on the PLL board made â€‹â€‹according to the scheme from the

Partly it's working but I still have some questions.
Let me begin by describing the elements.

MMC 2.16uF/650VAC WIMA FKP1
Coil: 6mm Cu pipe, 5 turns at 60mm diameter
Frez~ 156KHz,
Coupling transformer 4 ferrite core TX42/26 3E25
Halfbridge with IGBT, GDT, PLL driver

The controller is exactly the same as on the website. Tuned heater as described.
I set the jumpers as the author wrote, I found the resonant frequency has no component in the coil working. Output voltage bridge in zeros from the current bridge. Thoroughly placed the crossing by 0
Then I changed the jumper, the current was very large. When I put the charge to the working coil. Current decreased, adjusted the setting using the R5 to switch the output voltage is passed through the zero current.

Soon'll show all waveforms.
I am surprised that the current drawn from the supply is much larger without charge in the coil working and less when the coil is working load.

A moment ago damaged the bridge. I turned on the heater. I set voltage 200V. When the screw to heat up, the output current from the bridge to rise.
At some point damaged the IGBT. The current was very high.
I do not really know until the end how it should work. I ask you for help. I would like you to me explained step by step how I should set the driver.
I devoted much time to design PCBs and their assemblage. Also to make the MMC and the rest. I wish that this heater was operated stably and reliable. I tried to understand everything that was written in the guide. I do not speak English, please bear with us.

I still question whether the time set heater can work with different types of feedstock, or every time you need to set it again?

Greetings from Polish :)

TwirlyWhirly555

Sat May 10 2014, 04:48PM

Registered Member #4104 Joined: Fri Sept 23 2011, 06:54PM
Location: Uk .
Posts: 122

If the driver purely follows resonance , and there is not bridge current limit then with no load in the work coil resoant rise will cause the supply current to sky rocket as this is how series resonance works ( lowest impedance at resonance )

When the coil is loaded with a metal object the resonance effect is dampened causing the current draw to be lower than an empty work coil , as the object heats up the dampening effect is has on the resonance action drops causing the supply current to increase as well .

With 200V across the bridge and no current limit , with the driver following resonance it will cause a run away current rise as the work piece heats up to the point it melts or in your case the IGBT current limits were reached .

Robert2

Sat May 10 2014, 05:58PM

Registered Member #1773 Joined: Tue Oct 21 2008, 06:56PM
Location: Poland
Posts: 93

Thanks TwirlyWhirly555,
I read somewhere that because the frequency decreased to walk away from the resonance...

I took pictures waveforms.
Jumper J2 ON
Jumper J3 OFF
I set R6, R10 to half the voltage.
I plugged the bridge at low voltage 40VDC.
I set the frequency, J1 OFF R5 to get:

Sin- current output halfbridge, saquare voltage from halfbridge.

Jumper J2 OFF
Jumper J3 ON
Rest unchanged:

This is signal from pin 9 of PLL:

So experimentally changed the wires from the transformer coupling,
Jumper J2 ON
Jumper J3 OFF
I set R6, R10 to half the voltage.
I plugged the bridge at low voltage 40VDC.
I set the frequency, J1 OFF R5 to get:

Jumper J2 OFF
Jumper J3 ON
Rest unchanged:

At this point the course of a little flying, it was difficult to trigger the oscilloscope
When the work coil is empty, the heater operates at resonance, I noticed that the course of the upper transistor is bad. VGS:
The upper transistor:

The lower transistor at the same time:

I also noticed that the regulation of R10 when J2 OFF, J3 ON almost nothing changes.
When J2 ON, J3 OFF regulation R6 also almost nothing changes.
Connections to 74046 are like the diagram. These unconnected "hanging in the air"

Steve Conner

Sat May 10 2014, 07:03PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

The schematic shown doesn't have any current limiting. It just tracks the resonance. So it is working as designed, it is just not good enough for a practical induction heater. Try the Uzzors one instead.

Robert2

Thu Jun 12 2014, 07:23PM

Registered Member #1773 Joined: Tue Oct 21 2008, 06:56PM
Location: Poland
Posts: 93

Hello again!
I make new H-bridge and driver from uzzors :)
You are rights :)

WizardG

Fri Jun 13 2014, 02:14AM

Registered Member #43481 Joined: Tue Mar 11 2014, 06:15PM
Location: directly above the center of the earth
Posts: 4

How about a 1500 watt handheld rechargeable?

Robert2

Sat Jul 19 2014, 06:59PM

Registered Member #1773 Joined: Tue Oct 21 2008, 06:56PM
Location: Poland
Posts: 93

Can you explain why it is nicer voltage waveform when the current precedes voltage? I always thought that it is best when the voltage is switched in the current zeros. I enclose two pictures

Robert2

Wed Jul 30 2014, 06:44PM

Registered Member #1773 Joined: Tue Oct 21 2008, 06:56PM
Location: Poland
Posts: 93

I'm almost finished making a new housing

Gabriel35

Wed Mar 11 2015, 12:43PM

Registered Member #2310 Joined: Wed Aug 19 2009, 08:04PM
Location: Santa Catarina - Brazil
Posts: 169

Nice setup!

Experimentonomen

Wed Mar 11 2015, 05:21PM

Registered Member #941 Joined: Sun Aug 05 2007, 10:09AM
Location: in a swedish junk pile
Posts: 497

Why are you blocking like half of the radiator with the board ?

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