Dummy load rating

[KD6VXI]

Needed a load.   Found one.   It's Homebrew,  so no hard and fast ratings....   Wanted to see what others thought.

12 x 600 ohm 200 Watt Globar

Immersed in 50 gallons of mineral oil.

Since the 'cantenna' is a single 90 Watt,  and is good for 1.5 kw for 300 seconds??

Simple ratio says that's about 3.3 kw for each resistor.   So it should be good for 40 grand pep?  Seriously?

The seller used it originally to test as big as Collins 208U-10 and RF generators up to 10kw plate dissipation.

I wanted a 2.5 kw oil filled.   I believe I got it.

--Shane
KD6VXI

[KD6VXI]

Nobody?

Guesstimate?

I came up with my number by simple ratio.   

--Shane
KD6VXI

[flintstone mop]

All of that heat sink oil and the massive resistors should handle the boring QRO Ham Radio power all day long

[n2bc]

Did it come with a fork lift?  Must weigh the best part of 400 pounds.  My 1200W Bird weighs about 20 pounds.  I suspect you're OK.

73, Bill  N2BC

[KD6VXI]

No forklift,  but it does come on a furniture dolly!

I'm thinking it's going to live outside.

Comes with HN connector and an adapter to N.

Was Tucker Electronics bench load.

--Shane
KD6VXI

[Opcom]

600x12=2400 that's what ya got, CCS rating.

The rating while the oil is being heated could be a few times more. If you need more then a pump to move the oil will do better cooling but you must still remove the heat somewhere.

[KD6VXI]

600x12=2400 that's what ya got, CCS rating.

The rating while the oil is being heated could be a few times more. If you need more then a pump to move the oil will do better cooling but you must still remove the heat somewhere.

600 x 12 = 7200.....  You trying common core Opcom? Lol

My question about the ratings of this load compared to that of a cantenna was to see if it scaled as a ratio.....

I'm sure I'll never exceed its ratings,  but it will be nice to be able to not worry about heating at any normal power levels.

Would it be worth looking into real xformer oil?  I have friends I may be able to source some from,  so cost would be nil.  Is mineral oil that much 'less'  than real xformer oil (as used in pole mounted pigs,  current tech)?

--Shane
KD6VXI

[n2bc]

I don't know what the resistor network looks like, but if they were mounted in a perforated metal "can" (for shielding), simple ambient air flow would easily handle a few KW.  The best way to determine the basic capability of the resistors would be to open it up, get some part numbers and go surfing for heating specs.

Unless you're planning  tubes with handles, you're covered!

[flintstone mop]

We were always warned at Ft Monmouth not to tune the transmitters to full power, even though running into military style dummy loads located outside the buildings. They said that we can cause interference to Hams or licensed services on the shortwave bands.

You must be testing something really big.....

Do you think the FECES are going to raise our legal limit power?? In other countries legal limit is 2500W

[KD6VXI]

Fred,

It's a 50 / 55 gallon drum with an HN on top.   I haven't seen the inside.   I believe it's a 55 with 50 gallons in it to allow room for expansion.

As to what it's intended purpose is:  I wanted something along the lines of a 2.5 kw load that would take 2.5 kw for a while.   Like,  bird 2.5 kw load ratings.

While waiting for the right one at the right price,  this one came available cheap.   With 7.2 kw of resistors,  I know it will take whatever I throw at it (currently 3cx3000 powered,  something very similar to Opcoms current build).

My 'ratings'  I interpolated above was a ratio.   Based upon the Cantenna being a 90 Watt resistor and the cantenna has a 1.5 kw rating....   90/1500 is 7200/n

N was surprisingly large (120 kw  16.6 is the scale factor) ,  so I came to ask if you could / would scale the power values as such.

I run 'legal limit AM',  or will be when the rest of the station catches up to the generation department.   I'm currently trying to navigate permitting my towers.   TOWAIR says 40 feet max due to proximity to BFL.   I have a 60 and an 80 foot crank ups collecting dust on the ground. Once this is done,  antennas are in place,  I'll be able to move everything to the antennas,  rather than testing 😁

IOW,  it's to run my Homebrew Gates / RCA

--Shane
KD6VXI

[WD5JKO]

Shane,

  I don't know if this is a good comparison or not, but the link following describes why large oil filled utility transformers explode.

http://www.transproco.com/why-transformers-explode/

   The company I work for makes large power distribution transformers for 208/208 3 phase with insulation between the windings to hold off 250KV all day, 24/7. The power feed goes through a soft start SCR circuit, and each phase has extremely fast action fuses. Insurance companies dictate these measures, and even so they do everything possible to eliminate any oil filled transformers. We do use some similar air insulated transformers, but no more than 90KV isolation. Newer machines use a big motor generator with a 5' long insulated shaft between the motor and generator. These are good for 300KV isolation.

   Consider the safety aspects of overloading that dummy load ICAS, and something inside blows. If there is a surge in pressure, is there a pressure relief valve, and if so, will it control the pressure fast enough to eliminate an explosion?

Jim
Wd5JKO

[KD6VXI]

As far as I can see,  it does NOT have a pressure relief,  and that's one of the first things I planned on changing.

I am planning on it being outside as well.   Some have a doghouse for the tuna,  I'll have one for the dummy!  Lol

Appreciate the thoughts,  too!

Honestly,  I could drain the thing and air cool it for the power levels I plan on.   And have 24x7x365 duty cycle.

--Shane
KD6VXI

[Opcom]

600x12=2400 that's what ya got, CCS rating.

The rating while the oil is being heated could be a few times more. If you need more then a pump to move the oil will do better cooling but you must still remove the heat somewhere.

600 x 12 = 7200.....  You trying common core Opcom? Lol

My question about the ratings of this load compared to that of a cantenna was to see if it scaled as a ratio.....

I'm sure I'll never exceed its ratings,  but it will be nice to be able to not worry about heating at any normal power levels.

Would it be worth looking into real xformer oil?  I have friends I may be able to source some from,  so cost would be nil.  Is mineral oil that much 'less'  than real xformer oil (as used in pole mounted pigs,  current tech)?

--Shane
KD6VXI

I try to use everything within a CCS rating so I think I missed your point. To me the Cantenna is rated the resistor's rating and the other load is what it adds up to. Shell Diala is used in transformers. It's a highly refined mineral oil and will burn.