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Forum topic by kldehoff posted 08-28-2013 06:46 AM 917 views 0 times favorited 6 replies Add to Favorites Watch
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kldehoff

3 posts in 1194 days


08-28-2013 06:46 AM

I picked up an old unisaw (~1970’s era, 208V 3ph, 3hp with LVC starter and static phase converter) a few years ago, and it worked wonderfully through my first project. Then the starter failed.

My choices to get this back up and running are to replace the starter or to convert to a single phase motor and get a basic starter.

My current constraints are that I am no electrician, and I need to keep the cost to a minimum.

Any suggestions on which direction to go?

Thanks,

-Kevin


6 replies so far

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mantwi

312 posts in 1356 days


#1 posted 08-28-2013 07:56 AM

I just went through the magnetic starter thing on an old Grizzly 1023 I have refurbed and after weighing my options decided to forgo the magnetic starter in favor of a disconnect of the type used on air conditioning units. Picked it up at HD for under $20.00. After years of using equipment with the magnetic starter it occurred to me I have yet to need it. This is true of the thermal overload protection found in mag starters as well. This type of starter is designed for industrial use where machines are under continuous load and the possibility of a tripped breaker or over heating are very real. That’s not the world I operate in and a properly sized breaker will provide overload protection without the added expense. I have an old 3 phase switch I’ll let you have if you pay to ship it. I believe it’s rated 230/460, 20 amp, looks like a light switch in a fully enclosed steel junction box and weighs under a pound.

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kldehoff

3 posts in 1194 days


#2 posted 08-28-2013 07:12 PM

Mantwi,

Thanks for the suggestion. However, I’m not sure whether a switch rated at 230/460 will work with a 208V motor. I tried using a 220V-rated magnetic switch from WW Supply, but it just sparked at me and refused to catch.

Maybe I’m just being overly cautious.

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Loren

8294 posts in 3107 days


#3 posted 08-28-2013 07:15 PM

Sometimes a magnetic switch won’t work if you hold the
button in. It’s weird. My 3-phase trimmer does this –
the contactor sparks if I hold the button in but if I just
hit the button it starts fine.

My single phase European table saw starter needs the
button held in to come up to speed. It will start if
the switch is pushed and released but takes longer
to get up to speed. This may have to do with the
brake on it.

Magnetic starters get oxidation on the contacts over
time. The oxidation can be a real hassle to clean off
but it can help revive a switch that doesn’t seem to
work anymore.

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hydro

208 posts in 1211 days


#4 posted 08-28-2013 08:07 PM

You do not necessarily need to replace the magnetic starter to go from a 3 phase to single phase operation. A 3 phase starter is just a 3PST relay thrown by a single phase coil connected to one of the phases. To switch a 240V single phase motor just use two of the poles and run the coil off one of the contacts you are using for the motor. Leave one of the poles disconnected.

If you are unsure of how to do this pay an electrician to do it for you.

-- Minnesota Woodworkers Guild, Past President, Lifetime member.

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kldehoff

3 posts in 1194 days


#5 posted 08-28-2013 08:33 PM

Loren,

I had the same problem if I held the starter in or if it was pushed and released. It just simply never caught, so the starter got taken back.

Hydro,
The problem is that the starter doesn’t work (the motor is fine), and I don’t know enough to say whether safely replacing the starter for a 208V 3 phase motor is going to be more or less expensive than switching the entire setup to single phase for this saw.

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mantwi

312 posts in 1356 days


#6 posted 08-29-2013 03:16 AM

Oh yea, I know all about the sparks. My My Magnetic starter was lighting up like a bulb and it was black plastic. Scary stuff. If you go somewhere like Grainger they will have the part but it will cost you dearly. An electrician said that on equipment the voltage (208, 220 etc) refers to the nominal voltage required for efficient operation and it’s generally 10 to 15% below the maximum. 10% of 208 is 20.8 so 220 is fine. Besides that where do you get 208 volts in this 110,115 220,230 world? That being said in the long run switching over to single phase is a good idea. It cuts down on parts that can potentially go out at the most inopportune times and if you decide to sale someday most folks shy away from 3 phase. You aren’t being too cautious, a healthy fear of things that can fry you is not irrational it’s smart. If it was a Jet, Powermatic, Grizzly , just about anything but a Delta I’d recommend a call to their tech department but since Delta was assimilated don’t expect any help.

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