About my ZVS induction heater - Page 1
Forum section: electronics / beginners

author: metrologist
author_rank: Super Contributor
timestamp: December 04, 2017, 06:03:52 pm
content: I bought one of those inexpensive 1kW induction heaters and it works great. I was able to get a long 5/8" bolt glowing red hot. I also ordered a 40mm graphite crucible, but I am concerned that it is not working with that.The power supply is 36V 15A, and the voltage drops to 7V when the crucible is inserted into the coil, and the current peaks at 15A. When I remove the crucible, the current stays at 8A, but it is typically less than 4A with no load, so I suspect the voltage has dropped too low for it to operate properly and it goes into a self destruct condition. What should I look for to determine what is happening to prevent it from exploding the fets?Is there a way I can use this setup or do I need a better power supply? Maybe I just need heavier than 14ga wire

author: jcw0752
author_rank: Contributor
timestamp: December 05, 2017, 05:40:29 am
content: If your voltage drop is at the power supply then your wires are heavy enough. If the power supply reads much higher than what the voltage is at the load then perhaps the wires make a difference. I have a much smaller induction heater and I discovered that they had a quite high startup demand for current. Mine would not start at all if I hooked it up and slowly brought up the voltage. It would just draw a very high current but if I put the proper voltage on it immediately it would start. You could try adding a substantial capacitor on the out put of your power supply as this might help satisfy the initial high current demanded by the unit with the carbon crucible.John

author: T3sl4co1l
author_rank: Super Contributor
timestamp: December 05, 2017, 10:39:34 am
content: It's a toy, what do you expect?To get useful performance, you need a useful design. It would take at least a few small changes to fix immediate problems, but preferably many large changes to turn one of those things into a properly useful machine.Tim

author: metrologist
author_rank: Super Contributor
timestamp: December 05, 2017, 03:31:30 pm
content: I agree it is a cheap design, but should be sufficient for heating such a small crucible. One youtuber is using this the same way I wanted and in many more ways, such as spiral coil heating plates, but also with the same kind of crucible. He is using a very expensive power supply, 48V 50A, I think it was....Anyway, this one will start up just fine and will heat a 5/8" bolt to glowing, I just cannot get it to work with this crucible. The voltage drops at the supply output. I could get by with a smaller crucible too, so that is a cheaper thing to try.

author: gibbled
author_rank: Regular Contributor
timestamp: December 05, 2017, 05:07:17 pm
content: Graphite is conductive so I suspect you are heating the entire crucible rather than just its contents. Perhaps a non conductive crucible would reduce the power requirement enough to make it workable.Not certain, just beginning to play with them myself.

author: metrologist
author_rank: Super Contributor
timestamp: December 05, 2017, 06:45:02 pm
content: I wanted to melt aluminum and copper, for example. I think I need the crucible to get hot to melt these metals.

author: james_s
author_rank: Super Contributor
timestamp: December 05, 2017, 08:56:49 pm
content: If the voltage is sagging then your power supply (or wiring) is inadequate. If the voltage goes too low, these very basic Royer oscillator based heaters can lock up. The same thing happens if your power supply has too slow a rise time when you turn it on.