Induction brass annealer redux

[dskogman]

Blew another ZVS board after a year or so and lots of cases. This was the bigger 1800 watt version. I don't know how many blown components at this point but I thought this board with a Meanwell PS and Crydom SSR had it licked. Got another from Amazon and something popped as soon as it started annealing and of course doesn't work. Any way to find out what's blown and replace it or a reliable ZVS board?

 

[Bonio]

Nope,

Anemic Power Supply - get 750 Mean Well (48 volts) or Fluxeon ferrit inductor (no water cooling mess)

The power supply can put more power out. I wound a double layer coil and it was putting 12 amps out. It's definitely doing its 600w. It's what the MGNZ recommended to use with their control board which stops the zvs if it senses more than 12.3 amps anyhow so I'm thinking there's no point trying to use more power. I dont know though so I take on board what you say.

 

[itchyTF]

Are these current readings taken without any brass in the coil?

 

[Bonio]

Are these current readings taken without any brass in the coil?

Without brass about 8 amps with brass 10.5 to 12 depending where the case is and which coil I'm using.
I am re reading back at the start of the forum, someone mentioned coil orientation affects times, as in the top of the coil going to a certain side of the pcb.

is that a thing?

 

[kiwijohn]

@Bonio As far as I know the coil orientation makes no difference, but stand to be corrected. The biggest improvements I have made are
1 going to a flux concentrator type coil.
2 desoldering the middle bank of capacitors and attaching them back onto the underside to aid cooling
3 fans on both sides of the ZVS board to aid cooling
4 A shunt diode across the terminals of the +/- input for the ZVS board

As you have an MGNZ board can you not get an arduino ameter that wires in and shows on the display what amps you are getting?

 

[Bonio]

@Bonio As far as I know the coil orientation makes no difference, but stand to be corrected. The biggest improvements I have made are
1 going to a flux concentrator type coil.
2 desoldering the middle bank of capacitors and attaching them back onto the underside to aid cooling
3 fans on both sides of the ZVS board to aid cooling
4 A shunt diode across the terminals of the +/- input for the ZVS board

As you have an MGNZ board can you not get an arduino ameter that wires in and shows on the display what amps you are getting?

Thanks for the suggestions. Right now cooling isn't an issue it's all nice and cool, I'm still testing with just a handful of .308 cases.
I am using the current sensor with the MGNZ board which is useful. I will put a meter on the power supply to double check voltage under load.

Could you give me more info regarding a shunt diode? I'm not familiar with that. Likewise where would I get a flux concentrator?

 

[Bonio]

Induction brass annealer redux

Just made GinaErick annealer. First test with tempilaq 750F. I have zero experience with tempilaq. Which number is ok? What were the "burn" times for #3, 4 & 5?

forum.accurateshooter.com

That's where Hollywood suggested winding coil in different direction to reduce annealing times .

 

[kiwijohn]

So when the relay that closes for the ZVS board the power ( 48 V PSU) goes across the contact of the relay, when the relay opens at the end of the duty cycle to interupt the power supply, there is a back eddy of hign voltage that wants to keep the collapsing field held up. This is the back electro magnetic field (BEMF) that will jump across the contacts. By placing a shunt diode across the terminals, current will flow only in the one direction thus helping keep your relay intact.
Many of them burn out or fry due to this or because they are too smal.
Look up fluxeon they sell made up flux concentrators. If I do all the work for you, all you will learn is how to read and I think you can do that already.

 

[Bonio]

Thanks I'll try amazon for a shunt diode, I guess this will work with a solid state relay.

I'm going to try a different make of case when I'm back in the workshop just to make sure it's not the s&but brass that is the issue

 

[itchyTF]

The SSR may have an internal diode.

 

[Bonio]

Ah OK, it's just a single pole relay though it switches the negative side.

I guess none of this is the cause of the slow heating though. I'll rework the coil first then if that fails try a new power supply.

From what I have read (you are right kiwijohn I can read ) in this thread if my psu gets overloaded and drops the voltage half way through a cycle and then ramps back up whilst the zvs is still connected that could kill the mosfets on the zvs board? So I might be better looking for a psu that won't automatically reduce the power and bring it back up.

 

[kiwijohn]

Here's a photo of my spare zvs board with a shunt diode inserted at the terminals. This is the direction and place where I put it. I am using a SSR rated to 60V on the output side.
From the photo you can see I have extended the leads of the onboard LED so I can monitor the operational state of the board by mounting it on thecontrol panel of my builds. Also visible is the work done to the capacitor banks.

 

[Bonio]

Thanks for that. You say it's a spare zvs do these things fail often? I'm on my second but only because it arrived dead.

Thanks for the help guys. I'm re reading the thread again!

 

[kiwijohn]

I've built 3 and worked on another...none have failed, but I hear of it on here enough to have one in reserve. The way things went during the height of the pandemic, having a spare part seems optimal. This may even be a parts only one that you could solder up yourself.... I know one of them is. It was a very cost effective way to order it.

 

[Bonio]

I think I have it sorted, I made another coil, made it 26mm inside diameter. It runs at 7.5 amps with no case and between 10.5 and 11.5 with a case in. I just need to work out where to put the case exactly to anneal it properly but I can get the brass glowing red after 7 seconds. I guess i need to get some temperature paint so I know if I am doing the case properly.

Thanks for the help. I think I still need a better power supply, more cooling for the ZVS and I will add a diode when I work out the value I need.

 

[itchyTF]

The goal is not 750 degrees as originally thought.

 

[kiwijohn]

@Bonio for a diode Something BIG like 15A and 100V capable

 

[Bonio]

The goal is not 750 degrees as originally thought.

oh OK, ive been watching various youtube videos on the subject it seems like there are lots of conflicting ideas. What is the way to do it? Ive ordered some tempilq now in 750 degrees, should I send it back?

 

[itchyTF]

oh OK, ive been watching various youtube videos on the subject it seems like there are lots of conflicting ideas. What is the way to do it? Ive ordered some tempilq now in 750 degrees, should I send it back?

Yes, 750 is nowhere near where it should be. Can't remember exactly what the temp is but when it reaches the dull red glow in a dark room is about there. This has been talked about in this thread.

 

[Bonio]

Thanks Im wading through the entire thread again page 47 at the moment! I remember seeing a link to some videos on my first trawl through the thread that were done by a metallurgist but they seem to be behind a paywall now. not sure if its those I need to watch. Anyhow, plenty to keep me busy