3 phase motor question

[Bit_Fiddler]

I have a turret armed Delta RAS that I fixed up a bit. The 2hp motor appeared to run ok, but I also blew a LOT of dust out of it. Since I don't have 3 phase power, I put a TECO FM50 phase converter on it that is rated for a 2HP motor.  I bypassed the Delta motor controls per the vendor's instructions.  Seems to work ok almost all of the time.

Every once in awhile, especially after it hasn't run for awhile, the motor just stutters and hums for a bit when started until the Phase converter trips with an overcurrent warning.  Manually spinning or wiggling the blade back and forth before starting up the saw seems to eliminate the issue.  (To be clear, the blade is still and hands are clear before starting) Once running, it cuts & runs just fine...  

I have the FM50 set to spin up to speed in 2.5 seconds and spin down in 3.  I don't feel any binding when I spin the blade by hand.  The windings ohm out within 1 ohm of each other.

Any ideas what is going on?  Should I shorten the spinup time on the Phase Converter?

Thanks!
Dave

[HomerLee]

From my experience (electrical supervisor in a paper mill) I would say there is nothing wrong with the motor unless there is a loose connection on the wires supplying power to the motor. And I doubt this because loose connections get very hot under load, but it is worth checking. I'm betting the fault is in the equipment supplying power to the motor and that when the motor fails to start it is "single phasing", i.e., only two of the three wires to the motor have power. This is evidenced by the overcurrent. I would contact the manufacturer of the unit that supplies power to the motor and ask for technical help.

An electrician experienced with motors and motor controls could check this easily by wiring three pairs of 120 volt lights, each pair wired in series, and then connecting each pair to lines 1-2,2-3, and 1-3. Then when the motor tries to start and stalls, simply observe whether a pair of lamps is not lighted or is dim. This assumes the motor is 220 volt, if the motor is 120 volt then you would only need three 120 volt bulbs.

The again you might have a mechanical problem which requires more torque than is available, but this sounds unlikely since you are able to turn the blade by hand.

[Roly]

I second homerlee.   3 phase motors are pretty much trouble free compared to single phase motors.   The humming and just minor movement are signs of single phasing.   There is no centrifugal switch internal like on a single phase.   I too would look at the phase converter.   I have a feeling it is not always making contact to add the capacitor during the starting time.     Roly

[Bit_Fiddler]

Thanks Guys - I'll give Teco's tech support a call on Monday and see what they have to say....

Dave

[Bit_Fiddler]

Quick update, Called Factorymation.com today (Where I purchased the Teco FM50 phase converter) and they transferred me to a tech right away.  He gave me a couple of function settings to change in the FM 50 that he said would make more torque available for startup.  It appears to have resolved the startup stutter issue I was experiencing intermittently.

Good folks to buy from, friendly help up front,  quick easy to understand support 7 months after the sale.  Anyone ever needs an electronic phase converter, I'd recommend these folks in a heart beat.  No affiliation, just a happy customer.

Dave

[Roly]

Great to hear it was just a setting.  Roly