Resistive Ballast for SSTC

[Egg]

Hello. I was playing around with the 110v slayer exciter from labcoatz and decided to change circuit to function at 230v since I didn't want to be dependent on a transformer (mains 230v in my country). I used to use 6 150ohm 11w resistors in parallel as ballast for 110v and it was doing alright although it couldn't run for long. For 230v i connected 8 320ohm 11w resistors in parallel but now even if i run the circuit for a few seconds the resistors stay very hot for 2-3minutes and they would probably fail if i ran the circuit any longer.

My question is: What else can I use as a ballast? I have a few 50VA transformers but they are low inductance (around 15mH) on the thick wire side. Can I put the resistors inside water to keep them cool? I heard from someone that they could crack that way (?). Which ohmage and how many resistors should I connect to get a better ballast (I can get 11w ones for quite cheap). Is for example 100ohms from a single 11w resistor or 100ohms from two 11w resistors in series better (in practice)?

The output is really good and the mosfet doesn't heat at all so i know there is more potential if I increase the current.

Thanks,

[davekni]

Power resistors such as your 11W parts are designed to dissipate 11W when mounted apart from each other, allowing space for air to flow by.  Power resistors are usually mounted with a gap to ECB, sometimes even 2-3cm, to allow for cooling air flow and avoid overheating ECB.
Many power resistors are designed to run quite hot, hot enough to char ECB material.  300C case temperature may be normal for your 11W parts.
Measure current at 110V (or voltage across resistors).  Calculate resistor power.  Then calculate additional power for that current across another 120V.  (If using a DMM for measurement, that will miss high-frequency current, but still be close enough for rough calculation.)

[YSPACE Labs]

LabCoatz suggested using incandescent lightbulbs as ballasts. Makes sense since a 100W lightbulb is basically a power resistor meant to consume 100W of electricity. So different lightbulbs would give you different power consumptions. Paralleling lightbulbs (or putting them in series) would also affect the power the circuit uses.

[RoamingD]

As YSPACE Labs said, the lightbulb is probably the safest bet and you also end up with a dim bulb tester for other electronics  , but if you want something adjustable there are some Soviet Rheostats, basically 200-300w potentiometers.
A small hair dryer heating element can also be used, but you might have to adjust the number of turns accordingly to the resistance you wish to obtain. Good luck 

[Egg]

Thanks for the replies. I tried the bulb ballast however it is quite hard to find any high power filament bulb anymore and even if i did, it signficantly limits the output. I took your advice to sepetate the resisors and i guess it will do for now. I will be making a massive resistors bank soon to fix all the issues however i was quite busy since the secondary coil burned while i was playing with the 230v version output because or arcings. The secondary had some weak spots due to wire breaking while winding and i did not coat with epoxy (only did tape) which turned out to be not enough. I spent the weekend winding a new secondary with around 28gauge wire instead of 36 but with bigger radius and higher coil. The coil is also way better wound this time with epoxy coating. I might share the results here if everything goes ok.

[Egg]

Hi again. I got the build finalized and it works perfectly. I went with 8 220ohm 11w in parallel seperated  them as best as i could for air gap and added a small fan. I have done the cable management added a switch 10A fuse and terminal connectors. Here are some photos of it.