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Phase Converter questions

S

StinkBug

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I'm almost done with my new shop and I just had an epic deal fall in my lap. The owner of a local shop that closed a while ago finally decided to part with his Piranha 50ton iron worker for an incredibly low price so I just had to jump on it. Only problem is that it's a 3 phase machine, and there's no 3 phase service in my neighborhood. I have a 3 phase band saw in my current shop as well, and was debating on whether to get a converter, or just sell the saw since I dont use it much, but now I think the decision has definitely been made.

First question is how much converter do I need. The piranha web site says it has a 10hp 3ph motor. My saw is much smaller, and they will not be on at the same time.

Next where is the best place to shop for such a converter?

Thanks!
 
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K

kvom

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First check the motor plate on the ironworker to verify the HP rating. Then size your converter to match. For that size I would go with a rotary rather than a static converter.

I bought a 7.5HP converter panel from Anderson converters and supplied the 7.5 motor locally. I've been very satisfied with it.
 
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Defender Chassis

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You might look into a VFD. Tou will loose at least 33% of your power with a static phase converter. A VFD is a bit more money but it will keep you from turning thast 10HP machine into a 7HP unit. I just bought a 3-phase bandsaw and am going that route. The blade welder already worked on two legs of the 3-phase so I did not need to worry about that. Just a suggestion.
 
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dankeenan

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You can make or buy a rotary phase converter, then you can run more than motor at a time as lonig as the total hp is not more than your rotary.
If you use a VFD (variable freq. drive) you will only want to use it on one motor. Swithcing it back and forth can be tricky as the caps have to be fully drained or you may fry some parts on disconnect.
I use a VFD for my Bridgeport, it is a series one with belt and pulley for speed adjust. The main advantage of a VFD is you can adjust the speed via the VFD and not on the belt.

Dan
 
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A_Pmech

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10 HP! That's a mighty big ironworker...

The problem with hydraulic pumps is they take a lot of energy to start. As a consequence, the converter must be fairly large. I can *just* start my 10HP lathe with a 10HP converter, but it's a clutched machine so there is little load on the motor during startup. The hydraulic pump will heavily load your motor on startup.

Generally, a hydraulic pump or compressor takes 2-3 times the converter size. So, you're looking at a bare minimum of a 20HP converter to bootstrap that pump. That's well into pony start territory for a residential service. Thus, you'll have to build it yourself. There are no commercially available pony-start converters. I would copy the Fitch Williams design on Practical Machinist, up-rating as you go.

Alternatively, you might swap the motor to a single-phase unit. You'll still need a solid 150A service and a 20ish Kva transformer to start it.
 
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A_Pmech

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If the Piranha conforms to standard hydraulic practice then yes, the pump will come up to full pressure during the start and pop the pump circuit relief valve when the pump pressure reaches operating value. You could install a bypass valve in the pump circuit which would short-circuit the pressure side of the pump back to the reservoir. That would make things considerably easier to start. Once the motor has synched up, close the valve and bring the pump circuit to pressure. Still, you'll want plenty of rotary converter!

Nice machine, BTW! I'm jealous. :bowdown:

StinkBug said:
Are you sure about that? I thought the pump was only under load when you were actually operating the machine. Otherwise it's just idling. I could be completely wrong though.

This is the machine BTW
http://www.piranhafab.com/SingleOperatorIW_P-50.html
Click to expand...
 
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Torque1st

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Hydraulic pumps are very hard start applications. Check with the RPC manufacturers but I believe you will need a 20HP RPC. You can bypass the pump for startup but the pump also puts a huge load on the motor when it performs an operation.

I have a geared head 7.5HP lathe and it takes a 15HP RPC.

Check the hydraulic circuit, it could have a variable volume pump or even a two stage pump. The RPC manufacturer will need that information. You can usually hire a hydraulic system tech from a local fluid power distributor to look over the machine. 10HP is still 10HP and the manufacturer felt that size motor was needed for operation. If it only took 7.5HP I am sure they would have built the machine with a 7.5HP motor. Power is expensive.
 
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S

StinkBug

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ok after looking around a bit more it looks like I was wrong afterall, thanks for the info guys. So....any recommendations on a manufacturer for a 20hp rotary converter?
 
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A_Pmech

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Arco is a well-respected brand, although I have no personal experience with them, other than several conversations I had with their tech people years ago. My neighbor has a 100HP unit that he powers his grain elevator with and he's satisfied. They also have an online phase-converter sizing calculator.

Here's their recommendation for a 10HP 30FLA ironworker. It is their 15HP "Heavy duty" converter:

http://www.arco-electric.com/Recommendation.aspx?ItemID=30

I would ask them specifically for recommendations on installing their converter at your residence. Capacitor-start phase converters require a lot of inrush current to get them up to speed. You'll want to be sure your service is adequate.

If it isn't, you'll have to build your own pony start converter or upgrade your service. A pony start converter uses a small single-phase motor to get the main converter motor up to synchronous speed. Thus minimizing inrush current. They are very simple to build.
 
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S

StinkBug

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All the VFDs I've seen are in the 1-3hp range. That's not gonna be close to enough to power a 10hp hydraulic pump.
 
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Stuart in MN

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Certainly you can get VFDs big enough to handle this load - I'm not sure what the largest one is you can buy, but I've worked with 500hp drives.

As a rule of thumb, when using a VFD to convert from single phase to three phase you derate it by 50%, so for a 10hp motor you'd use a 20hp VFD. However, this may vary by manufacturer so it's best to ask their tech support for advice. There are a number of brands, the dealerselectric.com link above is one possibility.
 
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