Experience with static phase converter

dr sportster

Well-known Member
Okay so I picked up this nice South Bend lathe and it has a three phase 1/2 hp motor. I see on eBay static converters for sale about 50 bucks. I have no experience with static converters. Anybody have comments on these. Good idea bad idea?
 
I like them.

Just follow the instructions exactly, size it to or over your motor amps/hp.

You'll need to remove the fwd-rev control from the lathe and use the phase converter to start-stop-rev it. Most have the ability to remote wire to the existing controls if you want to keep your lever start or foot stop/brake. Just don't open or close the connection between the converter and the motor!
 
Like Steve says; I have one (off Ebay) on my mill matched to the HP of the motor. Works sweet. My forward and reverse switch works as it should.
 
I see one rated between 1-3 HP. So that one I assume would not work on 1/2 HP. I need to look at one rated 1/2 hp.
All the old wiring is outdated and will be replaced. If this works it is a cheap way to move forward.
 
I have one and it works fine. But anymore the VFD are coming down in price and for a lathe will work WAY better as you have infinite speeds.
 
For 1/2 HP you might be better off just getting a new reversible 220v motor. You'd be within a few dollars of a static converter without the hassles.
 
45 years ago, I helped my dad build static converters. You have both start and run capacitors. There is a rule of thumb, which I can't remember, for the size of start and run caps based on the Hp. The rule of thumb was to get the motor going, the we fine tuned the size of caps to get the best balance. Also used a 1 second timer to drop the starts out.

If I were you, I would find a HVAC business locally. They most likely throw away many 1/2 hp to 3/4 blower motors. My sister owns HVAC business. When they replace a unit, I sometimes have a request for her to save me blowers and motors. A good HVAC business will not usually sell used stuff, because they don't want a persone coming back complaining it went bad and them requesting a new part.
 
A consideration that you don't see mentioned by the VFD proponents is the age of the motor. The insulation older motors will not tolerate the voltage spikes from VFD'e under high loads. Check the lead in wires, if vinyl insulated you have a pretty good chance it will survive a VFD. if cloth it is suspect. I have had 8-10 various machines over the years that ran on statics or rotary and never had a problem as described below with reversing. No matter if your machine has a manual drum type reversing switch or is controlled by relays your machine will start, stop and reverse just like real 3 phase when run via static converter. If the machine has a step down transformer for control you need to be certain to wire it to the two phases that are not generated by the converter be it static, or rotary.
 
I used one on my mill. No problems. Took it off and hooked the mill to my rotary phase converter. Thinking about putting the static back into service since I have to run a 15 HP motor on my phase converter which uses more electricity. I need the 15 HP to run my 7.5HP lathe.
 
I have a static converter on a 3 hp lathe. Reverses with relays and works fine. You do loose some hp but I never notice it. I have a rotary converter on a 3 hp mill and it also works fine. Made it with a kit I got off ebay and a 5 hp 3 ph motor I had setting around. Have $125 in it. Was going to wire the lathe up to the rotary but it works fine so I don't mess with it.
 
Would a VFD work very well on a drill press? Will it have enough torque at low RPM turning a large bit in steel?
 
It will work at low RPM, but nothing takes the place of proper gear ratio for high torque applications. Not sure how much power you're needing or what drill press you have, but the VFD used along with the lowest ratio available might be enough. A VFD will also let you overdrive a motor, but continued overdriving is hard on mechanical components.
 
Best way to mess your mind up (and the drive) when designing a drive be it mechanical, electric or a piston engine is to confuse HP, torque and
RPM. Thus as Steve said A VFD does not replace proper gearing when the loads require a large percentage of motor capabilities.
In basic terms the maximum amps allowable through the windings is a constant no matter the RPM. If you cut the speed in half the horsepower delivered must
be cut in half by limiting Amp inputs. Also when you slow past a given point, fan cooling is affected and you must further derate or add
auxiliary cooling. Most motor manufactures begin RPM derates at around 80% of 60 cycle RPMs,
To be at its best VFD programming is rather complicated but not impossible to wade trough. On our Allen Bradley drives we program in peak amps
and peak amp time frames, continuous amps, RPM factors due to cooling fans. Some of our VFD drives that require full rated HP at reduced speeds
have motors that are 3 times the size than if they were single speed across the line starters.

So to answer your question if you leave your drill press in high gear and slow the speed down to 20% with a VFD two things can happen. A-If properly programmed it isnt going to have much torque to turn the bit. B- If not properly programmed it will pull the bit,,, for a little while before smoke rolls.

VFDS properly applied are great drives, they are not cure-alls.
 
(quoted from post at 07:02:15 06/26/15) Would a VFD work very well on a drill press? Will it have enough torque at low RPM turning a large bit in steel?

The VFD's prime intent here is to provide full true three phase power with reversing, soft start and thermal protection. Lower and upper frequency output should probably be 50 to 75Hz as per other poster's explainations of torque , current and power.
 
(quoted from post at 14:35:33 06/26/15)
(quoted from post at 07:02:15 06/26/15) Would a VFD work very well on a drill press? Will it have enough torque at low RPM turning a large bit in steel?

The VFD's prime intent here is to provide full true three phase power with reversing, soft start and thermal protection. Lower and upper frequency output should probably be 50 to 75Hz as per other poster's explainations of torque , current and power.
guess we should take that as a NO to Dusty's question?
 

Yes, no and maybe.
As long as the belts were used to provide primary control of chuck rpm. No problem. Modest tweaks of the motor rpms in the 60-75Hz range so power is not lost.
As you stated. If the drive was belted up at high chuck rpms and the motor dropped to 10 to 20 Hz. The drill press would be hard pressed to drill through butter.
 
Thanks guys, that's what I thought.
I have a nice floor drill press, I forget make. It uses 2 v-belts for changing speed. It's just that swapping the belts around to change speed is something that I rather not do.

Dusty
 
(quoted from post at 08:23:06 06/25/15) Okay so I picked up this nice South Bend lathe and it has a three phase 1/2 hp motor. I see on eBay static converters for sale about 50 bucks. I have no experience with static converters. Anybody have comments on these. Good idea bad idea?

For just a 1/2 hp motor I would be more inclined to just get a 1/2 hp reversible single phase motor and install that in place of the 3 phase.
 

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