1 Phase Motor on 3 Phase Power?

[woodworker]

I'm running a 1 Phase 220V Motor (Compressor) at a site that has only 3 Phase power. Hooked up to two lines but motor start is difficult. Power measured at about 205 VAC. I've been told to use a Buck-Boost Transformer? Does this sound reasonable. (I'm only into computers and woodworking)

 

[jbartos]

More info is needed:
1. Is the 3-phase system voltage 208V/120V?
2. Is there a normal/standard three phase transformer or two overhead transformers on a pole (open delta)?
3. What is Horsepower rating of your motor?
4. What are sizes of the power supply conductors?
The buck and boost transformer may or may not be the solution.

 

[woodworker]

I aasume it's a 120V 3 phase panel. 3-wire panel,110VAC from any one to ground, 205VAC between any two wires. Also running a 3-phase motor on a 24" wide-belt sander with no problems. Have 18" planer and an Edge Sander that are running single phase 220V motors between two wires from the panel (they're okay). Our copier, and all other tools are single phase 120V. We ran the compressor for 10 years with a single phase 220V motor until it had problems starting up, (and the bearings were shot). New motor is Dayton single phase, 220V, 5HP. (Like I say, I'm not electrical, I'm electronics and computer. To me black is ground {but I know not for electrical}). I assumed the 205VAC may not be enough to get a good motor start. The motor has 2 capacitors (I assume start and run). I just wasn't sure if it was good idea running 220V single phase things on two lines of three phase power. Buck-Boost threw me for a loop.

 

[jbartos]

Suggetion: Nowadays, some motors experience problems with bearings due to the poor electrical power quality. Voltage waveforms are contaminated with harmonics that arrived by the application of nonlinear loads (variable speed drives, inverters, electronics, modulation (Pulse Width, etc.)). Before, you start using the new motor, the power supply ought to be checked by a Power Quality specialized business for the harmonic contamination by using a harmonic analyzer to make sure that the new motor bearing will not be damaged soon. The present voltage Total Harmonic Distortion (THD) limit is 5% set by the industry standards (IEEE Standard 519, IEC 6555, etc.). If the 5% limit is exceeded, some suitable harmonic mitigating means shall be applied.

 

[JoeA]

You may have a capacitor problem or the 205V is too low to start the motor.
Why not consider using a three phase 208/230/460 Volt motor for the compressor. This will probably require a new motor starter to cycle the compressor on/off with the pressure switch. Once the conversion is made,future changes will be easy and the replacement cost for 3 phase motors are less than single phase when the HP goes above about 1 HP.





Joe Agro
joea@autodrill.com

http://www.autodrill.com

Please pass by our website.

 

[woodworker]

Now why didn't I think of that? I'll go pick up a new 3 phase motor. Sounds like that's the reason the bearing might have gone, and it should also solve my voltage problem. Thanks to all replies. I can save the single phase motor for use at home on my planer.