Creeker visit - in Ireland

[Paul Cahill]

I was home in Ireland for a few days to visit my parents, and Ian Maybury, a frequent poster here, kindly showed my Dad and me his workshop. My Dad is a lifelong woodworker, so it was a treat for both of us. We had a great chat – woodworking and tools of course, but everything else as well, and before we knew it a whole day had passed.

Ian has made great progress with the shop and will be spitting out serious sawdust before too long. He has his DC system up and running, with a metal Pentz cyclone he pieced together from parts he made himself and had made. It really sucks, with a 16” impeller. The major tools are Hammer – very nice, and a 24” Agazzani BS – a real brute.

One thing I learned that I was not expecting, having made the trip across the pond to America straight from college, is that the typical residential power supply in Ireland is about 60 amps and is very expensive to upgrade. As a result, 3 phase power converters are very attractive as a way of getting the amp load down. A 5 HP single phase motor draws way too much current.

So a big thanks to Ian for a great tour and I look forward to seeing the plans come to fruition.

[Ken Fitzgerald]

Congrats! I am jealous!

One of the places I would like to visit in the next 2 or 3 years is Ireland.

[Peter Quinn]

One thing I learned that I was not expecting, having made the trip across the pond to America straight from college, is that the typical residential power supply in Ireland is about 60 amps and is very expensive to upgrade. As a result, 3 phase power converters are very attractive as a way of getting the amp load down. A 5 HP single phase motor draws way too much current.

So a big thanks to Ian for a great tour and I look forward to seeing the plans come to fruition.

Wow, sounds like a great visit! The richest moments of life. I love reading Ian's posts, must have been a great visit.

The three phase conversion does have me baffled though. It was my understanding, and seems to be the case here in the states that you need roughly double the amps at 220V single phase as the stated amps on the three phase motor being powered. For instance my 5HP shaper takes 13A at 220V THREE PHASE, but the convertor that starts and runs it requires a 30A circuit minimum. Though I am not well versed in VFD's I was told a similar conversion factor exists there too. In a commercial shop that has 3P power available running machines 3P certainly drops the amp draw for a similar horsepower versus 220V single phase, but in most cases a converted load actually requires a bit more power to run as some is always lost to the conversion process. I'm curious to know if my thinking is off base on this? Perhaps he is also using a transformer and changing to 440V to cut the amps in half? I seem to recall some discussion of transformers when he started setting up shop?

In any even I know of several home shops running on 60A sub panels that do pretty well, but with a 200A main that leaves plenty of head room for the residence to operate.

[Paul Cahill]

The three phase conversion does have me baffled though. It was my understanding, and seems to be the case here in the states that you need roughly double the amps at 220V single phase as the stated amps on the three phase motor being powered. For instance my 5HP shaper takes 13A at 220V THREE PHASE, but the convertor that starts and runs it requires a 30A circuit minimum. Though I am not well versed in VFD's I was told a similar conversion factor exists there too. In a commercial shop that has 3P power available running machines 3P certainly drops the amp draw for a similar horsepower versus 220V single phase, but in most cases a converted load actually requires a bit more power to run as some is always lost to the conversion process. I'm curious to know if my thinking is off base on this? Perhaps he is also using a transformer and changing to 440V to cut the amps in half? I seem to recall some discussion of transformers when he started setting up shop?

Good points, but I am afraid I am not knowledgeable enough on power to answer them. Ian did mention that he is bumping the voltage up to 400 volts in association with the rotary converter for his bandsaw and he will use the same converter for multiple machines. The 5 HP 3P motor for the DC uses a VFD however, so that he can vary the speed. Maybe Ian can weigh in and elaborate.

Paul

[ian maybury]

Hi guys. Thank you for a fun day Paul. As before the last year of plugging away getting set up (machine and tool research and purchases, plumbing, heating, electrics, lighting and DIY dust system - the bench is next) has been a long and lonely road - so it was a pleasure to get to talk with somebody in the same space. Most of my friends after about three weeks of 'is it finished yet' have lost interest. Your Dad is a bit of a flyer considering his age.

Lest anybody jump to any conclusions and presume too much of my woodworking expertise my woodworking background has up to this been primarily home improvement with a Robland combo, so it's a bit of a journey of discovery for me too.

I should say that in this regard this site and one or two others have been of great assistance, and lots of fun too. Addictive actually. Thanks guys.

On the power supply issue Peter. The basic problem we have here is that most domestic single phase supplies are limited to 62A, with some more recent houses at 80A. You can get a larger supply, but since power is so expensive here it's relatively rare. The typical set-up is a transformer sub station supplying a group of houses with single phase power, getting 3 phase power is very expensive as our monopoly ex state power company really stuffs it to you. Maybe $2,500, even if the transformer is on the road outside. Not only that, but there's a hefty annual fee as well.

The first difficulty to be overcome in going for a Pentz style system (there's build photos of mine starting near the bottom of the page at this UK forum: http://thewoodhaven.co.uk/phpBB3/viewtopic.php?f=3&t=2048) is that if a 5hp single phase motor of the sort Bill recommends was available it would pull up to 80A while starting on our 230V 50Hz supply. In practice it's rare to see single phase motors here much above 2.2 or maybe 3kW. Add the possibility of a machine running at the same time and some domestic load as well and it becomes clear that this would lead to a pretty serious maximum demand problem.

The second difficulty is that a US spec 2 pole motor does 3,450 rpm, while they only do 2,850 rpm on our 50Hz power. This might have been OK, but centrifugal impellers typically tail off fairly rapidly at the high pressure end of the curve (above say 12 in WG) if you drop the rpm - and I wasn't too sure where I would be on total pressure drop in my system. So it seemed wiser to make sure the rpm was available.

To get around both of these issues I went for a single phase Yaskawa V-1000 VFD (this is a Euro model) driving an ABB 4kW 230V three phase motor. It cost a bit (around $300 plus panel and wiring materials) and was a pain to wire (shielded cable and grounding all over the place to prevent EMC/interference), but the soft start is magic. The 10 sec ramp up to operating speed with the current controlled by the VFD keeps the starting current drawn from the single phase supply down to only about 140% (= 15.4A total) of the roughly 11A @2.4kW/3.2Hp drawn with the fan running at a steady 3,150rpm. (the speed at which I took the readings) This is only about 5A over steady state, and is nothing compared to the above 75A and more that a single phase motor might draw.

The variable speed capability of the VFD delivers also means that it's possible to run at whatever speed is required within the limits of the motor and blower - although the nose level starts to climb pretty rapidly with rpm beyond the 3,450 the impeller is designed for.

On single versus 3 phase amps. You do get lower amps for a given HP/Kw in a 3 phase system compared to single phase, e.g. in the motor or whatever device it's driving. (that's in each of the three phases rather than one though) It's not much help though if you have to generate that three phase power by using VFD or whatever. This because setting aside losses due to inefficiencies and the like if your motor is drawing say 3 HP from the VFD you have to supply that same power from the single phase supply. Taking a 3HP/2.3 KW load approx as in the above example, that means around 6A 3 phase (in each of the three phases), but it takes a little over 10A in the single phase supply to power this.

You may wonder why a 4kW or 5HP motor on these systems when they draw only around 3.25HP max at steady state. The reason is that if more than one or even several blast gates are opened at once the HP drawn by the blower motor rapidly escalates. (blowers are a bit counter intuitive in that as you restrict the inlet the power drawn reduces) A 'comfortably' sized motor means that the motor is unlikely to suffer regardless of how you operate the system.

Against that the 3kW 3phase band saw uses a rotary converter (a device that runs a built in three phase idler motor from single phase power, and uses it to simultaneously generate the other two phases), and not a VFD. That's basically because the saw motor is a 400V 3phase unit (this sort of saw is realistically not available in single phase over here for the above reasons) that can't be wired to run at 230V (it's a 400V delta wound motor), and VFDs are not generally available over here from the major manufacturers that go to 400V from single phase. This it seems is because they can't easily be built to comply with the regulations regarding feeding electrical noise back into the mains power supply. Rotaries over here on the other hand often have a transformer built in to step the 230V 3 phase output up to 400V - this works just fine.

Another useful feature of the rotary is that it can run multiple pieces of equipment up to its kW limit (actually 5.5kW) - leaving enough spare capacity that if needed it'll run a 3 phase power feeder or something like that as well.

Rotaries don't do quite such a magic job of controlling start up current, but they are very effective in this regard too. The 24in Agazzani is quite hard to start with its big cast wheels, but even so it manages to hold the start up current drawn from the single phase supply down to a measured 17A or so.

ian

[Paul McGaha]

Sounds like you guys had a nice visit. Good for you.

I agree with Peter, I think Ian writes very well.

Here in America I guess we're fortunate that for the most part we dont have to worry about our electrical service. In my case, my house came with a 200 amp service, which is adequate for the house plus enough capacity to put a 50 amp sub-panel in the shop. I would think this would be typical for most people.

If we needed to upgrade our electrical service we would have to provide a new panel and service entrance conductors but we wouldnt have additional charges from the utility company. Not nearly the problems or the costs that Ian is dealing with.

At least thats how it is where I live.

PHM