OK nothing to do with Landrovers but some of you chaps move in suitable circles to come across these things !
I'm looking for a large (50KVA plus up to 150KVA) diesel 3 phase generator - preferably in an accoustic cabinet but beggars cannot be choosers.
Anyone know of any standby sets being de-commissioned and looking for a home? Preferably in the South.
AWEM
Bloody hell what are you powering, the Queen Mary?
Peter.
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Induction furnace
AWEM
....with which to smelt the Queen Mary. ;o)
Steve
Big Sis recently sold 3 on Ebay so try there. She ran a Livery yard in an area which doesn't .. or should I say didn't have mains. She has lots and lots of lighting.
Lee D
There's a 150kVA Detroit Diesel powered genset for sale here at a latitude of 37 degrees S. That's possibly a wee bit far South for you though. :-)
andrew ive mailed you direct about one i have at work available, plus there is most likely more available but youll need to ring my boss as he deals in all thats stuff in a big way . regards, ian
Ian,
Thanks - nothing received - did you de-spam the return address?
Andrew mawson org
Ebay has a 50kVA detroit trailer mounted but in Northumberland not quite as far... Worth looking at ebay there are normally one or three generators of 50 to 150kVA size at any one time.
Do you do open days?
AJH
Would you be brave enough to attend one
AWEM
Actually, I would be quite interested in seeing a small induction furnace system Steve
Steve,
You would be very welcome to call by and see it - the big 'Beast' isn't connected up yet due to absence of big generator - I have a little 'demonstrator' that I knocked up (250 watts as opposed to
100KWatts) which doesn't melt anything (other than solder), due to it's low power but shows the principle.I'm in Bromley by the way.
AWEM
Hi Andrew,
Bit of a trip to see you specially, but its technically something I'm interested in - can you heat things up to 1700 degrees by induction realistically ? I'd guess as 4-5 kW ?
Steve
Try me ;-)
AJH
Upper temperature limit is not specifically limited by the power you apply. There are two effects happening in an induction furnace:
A/ Magnetic hysterisis - happens up to the 'currie point' of the metal (850 C for most steels) - the violent twisting of the magnetic domains heats the metal. Above the currie point the metal is no longer magnetic and this effect ceases.
B/ I (squared) R heating - the charge acts as a shorted turn in a transformer with vast circulating currents heating the metal by resistive losses. This effect is less in better conductors like copper and aluminium and more in steels.
Power input and radiant and conductive losses limit the temperature that you achieve - maximum temperature is when input power and power loss are in equilibrium. Given good thermally insulating refactory materials and enough power there is no problem reaching 1700 C.
My 'Beast' can dissipate 100Kw in a tiny 12Kgs of stainless steel which should melt it in quick order (if I can find a suitably rated and price generator !!!!!)
AWEM
How about graphite ? Trouble is at that temperature, you need serious radiation shielding or all the heat radiates off. And the best materials for those are all bloody conductors.
What kind of power transistors feed that then ?
Steve
temperature
serious
materials
rated
Steve,
Graphite being an electrical conductor heats up significantly - my 250 watt 'demo' setup uses a clay/graphite crucible and it gets the crucible hot with no charge in it.
Output semiconductors are eight whacking great thyristors (an 'H' bridge of four series pairs) with a further two slighlty smaller ones to turn 'off' (comutate) the bigger ones once fired into conduction. These are chopping a DC supply (500v @ 250 amps) to give a 3000Hz square wave, which becomes a sine wave when applied to the furnace coil and its associated capacitors when at resonance.
AWEM
On or around Fri, 11 Nov 2005 23:09:48 +0000 (UTC), "Andrew Mawson" enlightened us thusly:
I notice the engineering place that does crank regrinding and so forth not far from here has uninterupible powre supply sets (large ones) listed for sale on his notice board. dunno details, though.
I thought you'd have used IGBTs - I always forget about thyristors, because they are bastards to turn off. I don't remember the first thing about thyristor commutated bridges - its 20 years since I did high power electronics. From the depths of my memory I drag up the words "McMurray inverter". Is this one ? I can't find a piccie online to check it.
Is the resonance stuff to force the waveform to be a nice low emission sine wave then ?
Maybe we should take this discourse on power electronics to email !
Steve
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