I know it is not the best solution.....

[bradodarb]

I just bought a Kondia knee mill that has very low hours and is reported to be from an early eighties Intel plant. It has an approx. 2hp motor(240/480-3) 4.5 amps and a switch that has forward,reverse and stop, no electronics (pretty simple!?!) I was given a while back a static converter that is rated at 5hp@15amps. I have wired the motor to the 12 possible leg combinations systematically. I can only get the motor to spin at about 100 rpms. The motor is rated at 1800 rpms. I took the motor to work to test it on true three phase, and it runs great, just a simple 3phase motor. Lets call the input 220v L1 and L2 and the legs U,V and W. When I test U,V or W to ground I get between 119 and 121 volts. When I test against each other, I get the following:

U-V = 244vac
U-W =244vac
V-W =1vac

W-L2 =244vac
v-L1 =244vac




So the motor is "single phasing, right?"


Is my converter shot?

I plan on eventually installing a VFD, but I thought that I should at least be able to have some fun with the converter.


Please help.


-Brad

[Al_The_Man]

It sound like single phasing, try setting up a resistive load between the phases out. In a pinch you could put 3 sets of 110v Lamps paired up in series. and recheck the voltage across each pair.
Your Static convertor output may not be referenced to ground, if not those readings are meaningless.
Most VFD are not BTW.
Although you should always ground the motor.
Al.

[bradodarb]

Al,

The converter is connected to my house's earth. It has three wires coming in from a dryer outlet,black,white and green. The converter has the 2 inputs plus a green earth post. I have U,V and W coming out to the motor via a 10/3 sd cable and a separate 10awg wire going from the common earth to the motor as well. Does that sound about right?

I am not sure that I am following you, can you tell me if I got it:


01=light1
02=light2
03=light3

|---------|-G
|converter| |
|________|03
| | \
U V W ___/
\ / \ /
01 02

Forgive my crude graphic and my ignorance of AC. I have been so focused on lurking around here to absorb all that I can on the other side of machines that I am only now trying to pick up on basic three phase circuits.



Thanks for your help, maybe I'll have this bessey going by tonight after all.

[Al_The_Man]

If you rig the light test up you would have a load/light pair between U&V, Pair between V&W, and a Pair between W&U (delta connected).
Keep the ground from dryer plug to convertor.
Forget the motor ground connection for now.
Although it sounds like you are not getting the artificial phase, This test may confirm it.
Al.

[bradodarb]

Al,

When you say "load/light", you are talking about?:


U-motorlead-01-V

V-motorlead-02-W

W-motorlead-03-U

I wil give it a try, thanks

[Al_The_Man]

Yes, I think you have it.
Al.

[bradodarb]

Al,

In case I cannot get this done until later, what results am I looking for?
I have to deal with SWMBO.

[Al_The_Man]

Essentially this is a test that all phases put out the same voltage, you should have equal voltage between any two phases. Check the phase you had missing previously.
Al.

[bradodarb]

Al,
Thanks for all the help. I guess I had a blown capacitor in my converter. I decided to just hook up a Hitachi L200 and problem easily solved. Inverters are definitly the way to go when you have a low powered simple application like mine.

I still need to build a 15 hp RPC for the lathe though...