What Size Phase Converter do I need?

Holy Heat, Batman! How many watts is that?

I'm of the opinion that you should look for a different kiln. There are no shortcuts to providing the needed wattage---be it with three phase or single phase. The demand on amperage for the phase converter will be just as great as if you went single phase directly to the kiln, so I see nothing gained with the three phase unit aside from lower amperage per leg. Overall, you'll still consume the same amount of power, and you'll be paying for the phase converter and its losses in the bargain. You'd be better served to buy a kiln that is single phase, with a higher current demand (because it's only single phase)-----and avoid the phase converter. I'd have a totally different attitude were you powering a machine tool. I wonder if Bruce would agree?

Harold

0 HP. No reason to use a phase converter for a non motor, resistive load. Rewire the kiln for single phase, unbalanced if necessary, or find a single phase kiln.

Unless you got a real steal on the kiln, _and_ it can be easily rewired for 220 single-phase, I agree with Harold.

Three phase power is great for rotating machinery, because you get better starting torque and smoother running.

Three phase power is nice for he-man power electronics because you need less (or no) smoothing capacitors after rectification.

Three phase power has little advantage other than smaller wires for heating, because a heater doesn't care if the power is perfectly constant or if it pulses at 120Hz -- it gets just as hot either way.

Were it mine, I'd look to see if the heaters are connected in a delta, and if so I'd say "yipee!" and reconnect them in parallel for single- phase operation -- unless I had to buy enough parts that I could just get a new kiln.

If you have to ask, I'm not going to recommend that you do the above -- just check to see if it gives directions for wiring it as single-phase, and if it doesn't start shopping around for a unit to replace it with.

I would expect it to be fairly easy to rewire the kiln to use single phase power. Who makes the kiln? And what model is it. It is very likely that you can use the existing elements. The worst case would be that you have to install new elements. Which would not be all bad as elements age and fail. So you would be starting with new elements. You can get new elements at Seattle Pottery.

Dan

Approximately 25 HP.

You should also check whether the kiln can possibly be rewired to run from single phase, at full power or at least partial power. Is there a blower or a fan inside?

i

Thanks for all the answers (and non-answers) everyone. I'm looking at a lightly used kiln and less than 1/2 of what it would cost new. I think the main reason is the 3 phase requirement.

It's a Skutt 1227 if that helps in your answer.

I HAVE a 5HP phase converter for a roller, but someone else said it would take 40 HP to do it. I don't know what it would take to rewire it to single phase... that sort of thing is way above what I know how to do, generally speaking.

I really need a kiln and this one seems priced right, but not if I NEED to get a huge-ass converter.

James (seattle-ish)

You are looking at a 11 kW kiln. A year ago I bought a 10 kW kiln for $50. It was single phase. Half of what it costs new, does not sound so appealing to me personally, for a 3 phase kiln. An easy to find deal on a 10 kW kiln is about 300-400 dollars. Far less than what a phase converter would cost. Besides, a kiln runs only intermittently, in short bursts, but the phase converter would have to run continuously, adding to the cost. If you do not know how to rewire a kiln, a phase converter in size required, would cost more than a new kiln, or at least about as much.

To me, it is either rewiring it or looking for a diff. kiln. For rewiring, the price has to be "almost free".

i

James,

1. Call Skutt, ask them if it can be rewired to single phase.
2. Get a 15 hp rotary converter.
3. Get a 15 hp VFD on ebay. Dave

30 seconds with google shows that Skutt do make a single phase 1227 so next step would be to ask them what is involved in changing from 3 phase to single phase and work out if it's worthwhile.

Hey James,

Welcome back. Merry Christmas. Drop in more often.

220 VAC at 31 amps works out to 6820 watts. Using a loose rule of thumb, it takes 750 watts per horse power. Therefore, your kiln is equivalent to a 9 HP motor, and rotary converters are derated by as much as 50%, so you would need a 15HP 220VAC 3-phase motor set up as the rotary convert or to accommodate it, IF it was a motor. But it's not. I suspect that there are also reasons other than the heaters that this is three-phase. So, best advice was given by another...... Try contacting the manufacturer, and if they can't tell you, ask for a schematic, and get back to us.

Take care.

Brian Lawson, Bothwell, Ontario.

it is three phase 31 amps, do not forget. So the power is 1.73 times more.

i

About 20HP would do it. I'd really consider rewiring it to single phase which would draw 54 amps. With the RPC you are going to draw more to run the motor + cranking up 20HP might dim your lights depending on the size of your service.

My 5HP starting up flickers the lights a bit out in the garage.

I seem to remember something about 3 phase keeping the elements powered longer but I don't see how you get past P=IE no mater what you do.

Wes

Further reading brings up these statements:

Three phase operation. Only special order Models KS-1027, KS-1227, KM-1027 and KM-1227 will operate on a three-phase supply. However, any Skutt kiln can be properly powered via unbalanced connection to two of the three hot wires of a three-phase supply. Of course, the green safety ground connection provided in all Skutt power cords is also used.

Three-phase installation. Three-phase models KS-1027, KS-1227, KM-1027 and KM-1227 can be plugged directly into a three-phase (15-50OR) wall receptacle.

208 versus 240 supplies. As you can see from the chart, most Skutt models are available in either 208 or 240 volt versions. The exceptions are models KS-714 and KM-714 which are universal, and will fire with 240V or 208V power. The "120/208V" supply is increasingly encountered in schools and newly built communities, because it is more efficient for heavy 120V loads. This affects models KS-818, KS-818WR, KS-1018, KS-1027, KS-1227, KM-818, KM-818-30A-3, KM-1018, KM-1027 and KM-1227 because their elements receive the full 208 *or 240) applied volts. The 208V versions should never be fired on a 240V supply without first installing a full set of 240V elements. Otherwise, all components will be seriously over-taxed.

RoyJ wrote:

Looks really easy to covert, unless I'm missing something

Move two wires on the terminal block.

Thank You, Randy

Remove 333 from email address to reply.

I got a note back from Skutt tech support, it'll cost around $400 in parts (plus labor if I don't do it myself) to get it to run on 240v.

Now I just have to decide if I can afford the kiln plus that...

Thanks for all the advice.

It's true, I have been GONE for a while, not that I was ever a huge poster here. Life's been good and bad... got divorced, sold a sculpture to the City of Issaquah (washington), got skin cancer, had the chance to go to Africa (and TIMBUKTU) on someone else's dime...

Now I just need to sell a sh*tload of ART to pay off the divorce loan I got... it let me keep my shop!!! (but I have 1 1/2 years to pay it back or I have to sell it all.)

What's that you say? too much information?? hehe

Happy winter everyone!

James, Port Orchard, Washington, USA, Earth

In the words of someone with four bypasses and five divorces (or was that the other way...) "Why get married? Instead, buy a house for a woman you hate".

This > Life's been good and bad... got divorced,