The Table Saw That I Built

[rbarshaw]

This is the cutoff saw I bought at auction for $10, It has been greatly modified to get to this point. It used to hang overhead and swing the blade across this table I've now built the blade and motor into. I still need to mount the controls and guard and come up with a guard for the 16" blade. I've already tested it and can cut thru 4" thick pine ok, the blade needs sharpened tho.

A little more detail on the motordrive, 3HP 230vac 3Phase motor. 15" belt I had laying around. the shaft, blade, bearings, and motor came with the saw.

A guard I need to cut to size and mount over the belt.

The big box is the start/stop switch for the saw and the little one is for the start capacitors, still need to figure out mounting.

The start capacitors are the 4 black ones that add up to 120mfd, the other three are run caps that total 72mfd. Rule of thumb that I learned is to use about 60mfd per HP. to start and about 25mfd per HP. to run, the run and start mfd are added togeather to give the total for starting the 3phase motor on single phase power.

A rear view of the saw.

A future rotory converter, 10Hp 230vac 3Phase.

[Al_Smith]

A little word on the phase converter.As a normal rule,it's 7.5 microfarad per Hp,on 240 volt,for the running capacitor .You need to keep your dummy,or manufactured leg below 300 volts.You can adjust this by adding capacitance to increase the voltage,or decrease to lower it.When using a 3 phase motor on single phase,it will only put out about 60 percent of it's rated power.When using a 3 phase motor as a rotary convertor,the motor is at rated power,and runs at about 92 percent power facter.A properly wired convertor will start the same hp motor as the convertor is made from and run about 3 times the amount.I've made about 25 convertors and had excellent results.My shop is ran with a 5 hp.The resulting voltages are 481,481,478,so it's real close on the capacitance.I used 2 ,10 kva control transformers,back fed to get the 480 volt single phase,then through the convertor,for the 480 stuff.I have a few older machines that have straight 240 volt motors.For these loads,I used a 15 kva transformer to reduce it down to 240,3 phase.One of my on going projects is to put together a 10 hp air compressor,so I see a larger convertor in the future ;D

[thedeeredude]

Don't let OSHA see that thing  

[Buzz-sawyer]

Nice work
Are you planning on using it as a cut off saw or ripping saw?..........It sounds like it was originally a cut off.......you may not be able to rip with the blade ya have (you probably know the difference) ;)

deerdude You would really like to see my open 56" blade running then :D :D :D

[Don P]

Nice saw, How come I only hear about deals like that 8)  I've thought about something similar between roller tables with an angle iron fence for edging.
Sounds like y'all know your stuff on making 3 phase  8)
I've toyed around with the idea of scrounging parts to make about a 40 hp rotary and then drive that size motor on my mill. The power co says I go into commercial rates at 30 kva...is there anyway of knowing ahead if I'll cross that line  ???

[rbarshaw]

Al_Smith--- I have 235, 238, 240vac across the phases on that motor. I wonder how I managed that.

thedeeredude--- What's OSHA? Just kidding.

Buzz_sawyer--- That's a cut off blade now, but at that same auction I got 13 16" ripping blades that will work on this saw, and they are all new  8) .


Don_P--- I,ve got the rollers to make in and out feed roller tables. A pipe clamp with a straight edge fastened to it makes a good fence. About the 30 kva I don't know but someone here could figure it out, i'm shure.

[Al_Smith]

Not bad on the voltage,you're in like Flynn. 8)

[Al_Smith]

Another thought crossed my mind.When repowering sawmills,compressors etc.with elecrtric motors,a 3 to 1 factor is about right,in most cases.In other words a 10 HP motor will replace a 30 Hp gas or diesel .What is somewhat confusing is the way elecric motors are rated .The only true rating is 746 watts per horsepower,at 100 percent power factor.An advestising ploy is to sell motors at "developes ,blah blah Hp"A typical 5 hp motor,single phase,using this method is only about 2.2 hp,in actuality,check it out.This misleading rating system is only used on the cheaper motors.If in doubt,check out the nameplate running amps,and figure accordingly.I brought this subject up because I've seen people get sucked into those cheap motors and be less than satisfied with the results.On 3 phase motors,the rule of thumb is 2.5 amps per Hp,unless it's some cheap  imported motor,which I ,personaly,would stay clear of.

[DragonsBane]

Ok now my interest has been peaked. Can anyone send me some schematics on the wiring necessary to build a rotary converter. This could open up a whole new area of experimentation.

later all....

[rbarshaw]

DragonsBane--- My laptop is on the fritz till new parts arive, so I can't get to the files on there, but if you search the web for 3 phase systems, ie; '1 phase to 3 phase' or 'rotary phase converter', etc.

in the simplest form a rotary phase converter is just a 3 phase motor setup to run on 1 phase then the 3 lines on the motor that have 1 side to the incoming power, 1 side with the capicators and, one side with no connection, are just run to the 3 phase motor you want to run. It acts like a 3 phase alternator. This does not include all the breakers and safety devices.

[Don P]

Mine started out as a static converter, just capacitors . It ran a 3 horse 3 phase blower. I scrounged  a 5 HP 3 ph motor and run that as my idler now. That makes it a rotary phase converter. The idler motor is basically generating the missing leg.

I would tell you how I wired it the first time, but I burned up the evidence. You probably wouldn't be satisfied with that way anyway.

This is how mine is wired;
http://www.metalwebnews.com/howto/ph-conv/fig1.html

The article for that schematic is here;
http://www.metalwebnews.com/howto/ph-conv/ph-conv.html

I think someone was running a 50 HP saw with homemade converter and doing it on a 125 amp breaker...My electrical ignorance shows, that means he's doing it under the 30 KVA commercial limit my power co was talking about?