Rotary phase converter question

[Anonymous-0]

I bought a 13" South Bend toolroom lathe with a3 phase motor and I got a phase converter with the deal. Igot everything working and find that I must have a bad bearing in the phase converter.It rumbles alot. Do I need to be careful in taking it apart be cause of capactors holding a charge that might wipe me out? I never quite understood all that stuff, but I remember fella's leaving charged up condensors from point ignition lay around on the bench for unsuspecting people to pickup and get zapped.
Thanks for any advise.

 

[buickanddeere]

The price has dropped so low on variable frequency drives. Sometimes it's better to use them instead of a rotary converter.
Plus a vfd offers speed and torque control.

 

[JMS/.MN]

Capacitors will discharge if you touch both sets of contacts with a wood/plastic handled screwdriver. Don"t touch the contacts with your fingers before that. If it sparks, you know it is discharged.

 

[Sam#3]

A capacitor charges to the peak voltage that is applied to it. ie. 120vac x 1.414 = 170v or if you're working with 480vac it's about 700v. Power caps. have a lot of capacity so they can be letal and even if not you may wish it been.

 

[Bus Driver]

In addition, the inverter/VFD is much more efficient and is noiseless. The VFD disadvantage is that it will power only one motor at a time. The books for programming the VFD appear daunting at first. You will like it when you get accustomed to it.

 

[Bob]

Here's a GREAT resource...
Get Practical

 

[MF24-4]

What is a good inexpensive inverter vfd?

 

[big jt]

Don't know what brand you have and not sure that makes much difference.

Most Rotary converters are based on or built out of a 3 phase motor. Shouldn't have to open up the capacitor box to replace the bearings, just take the end plates off.

If you do need to open up the cap area just do as others have suggested. Yes they can hold lethal charges but it doesn't take much to disapate it

jt

 

[Bob]

JUST because he MAY not have to open the cap box to change the bearings doesn't mean he couldn't get zapped by a still-charged cap by touching other ;arts of thenunit!

 

[buickanddeere]

(quoted from post at 09:41:47 04/09/11) JUST because he MAY not have to open the cap box to change the bearings doesn't mean he couldn't get zapped by a still-charged cap by touching other ;arts of thenunit!

How is a capacitor which is connected across the motor windings stay charged after the AC power is removed and the motor stops turning?
Measure the motor winding resistance. The winding short out the cap and discharge it in milli seconds.

 

[MattE]

More than likely if it's rumbling it's not the bearings. Put a load on it with the lathe running and see if it smooths out. If so, or at least you notice a change than it is just a cap matching problem. Measure the voltages on all three phases they should be within 10%

 

[Anonymous-0]

Thanks for the advise. The website from Bob was real helpful. This site always seems to have a wealth of knowledge. It's good we are not all paper pushers with no practical Knowledge. Although we need some paper pushers.