Used rpc blew

John.t.little1

Aluminum

Joined

Oct 10, 2014

Location

St. Augustine, FL

• Nov 4, 2014

• #1

Picked up a used rpc 10hp wired it up it ran my lathe fine powered it down came back went to power it up again and the drum in the motor sounded like it was scraping. Sparks and smoke everywhere. Took it apart and two parts of the windings are burnt on both sides. Any idea the cause?

 

J

jakefreese

Hot Rolled

Joined

Aug 4, 2012

Location

TEXAS

• Nov 4, 2014

• #2

how old of a motor ? many older motors can not take the voltage spikes from vfds.

 

John.t.little1

Aluminum

Joined

Oct 10, 2014

Location

St. Augustine, FL

• Nov 5, 2014

• #3

It was a phasemaster ma-2 not sure how old in thinking 10years or so.

 

G

gustafson

Diamond

Joined

Sep 4, 2002

Location

People's Republic

• Nov 5, 2014

• #4

thinking if it ran fine that it was not shut off properly/wired properly in some way that it still was loaded when you shut it off

 

JST

Diamond

Joined

Jun 16, 2001

Location

St Louis

• Nov 5, 2014

• #5

Is that the lathe motor or the RPC idler?

If the lathe motor, maybe there is a problem with the RPC wiring or switching....

If the RPC, then possibly the start setup did not properly disengage, assuming it has a relay for starting. That could affect both motors, actually.....

jakefreese said:

how old of a motor ? many older motors can not take the voltage spikes from vfds.

Click to expand...

Considering that an RPC is an ALTERNATIVE TO a VFD for making 3 phase, maybe that was not a factor.......

 

J

jakefreese

Hot Rolled

Joined

Aug 4, 2012

Location

TEXAS

• Nov 5, 2014

• #6

JST said:

Considering that an RPC is an ALTERNATIVE TO a VFD for making 3 phase, maybe that was not a factor.......

Click to expand...

Where is the face palm emoticon? I had vfd in my head.... It has been one of those months....

Have you been able to verify your wiring? Over current could have done that, or over heating.

 

John.t.little1

Aluminum

Joined

Oct 10, 2014

Location

St. Augustine, FL

• Nov 5, 2014

• #7

I wired it exactly how the instructions stated and there was no relays in the motor it was just 8 caps 4 start 4 run.

it was the rpc idler. I had the wires ran from the panel to a 40a fused disconnect than to the rpc from the rpc to a 20a fused disconnect and lastly to the lathe. The L2 40a fuse is the only fuse to go out. Also threw the breaker.

 

C

chuckey

Stainless

Joined

Jul 21, 2005

Location

Wensleydale, UK

• Nov 5, 2014

• #8

In pic #1 at about 11 o'clock, there is a little white particle on the winding - what is it?, also there is a scrape mark on the rotor. Was there a bit of swarf rattling about?
Frank

 

W

woodsrider845

Hot Rolled

Joined

Dec 12, 2012

Location

ny usa

• Nov 5, 2014

• #9

That armature looks like it has been rode hard and put away wet. I'm betting it was at the end of it's lifespan.

It happens. And that bearing looks like it's been beat like a red headed step child.


Just sayin'.

 

J

jakefreese

Hot Rolled

Joined

Aug 4, 2012

Location

TEXAS

• Nov 5, 2014

• #10

chuckey said:

In pic #1 at about 11 o'clock, there is a little white particle on the winding - what is it?, also there is a scrape mark on the rotor. Was there a bit of swarf rattling about?
Frank

Click to expand...

That is one of the winding leads. It most likely needs a rewind, and some new bearings.

 

D

DaveKamp

Titanium

Joined

Oct 3, 2004

Location

LeClaire, Ia

• Nov 5, 2014

• #11

Hmmm... my bet, is that it was probably compromised before you bought it... if not, I'll second JST's suggestion that the starting circuit didn't disengage properly. That's certainly smoked...

 

John.t.little1

Aluminum

Joined

Oct 10, 2014

Location

St. Augustine, FL

• Nov 5, 2014

• #12

I called the local shop they said a rewind starts at 750$ not including parts for a 10hp. So I figured if just build a new one.

 

JST

Diamond

Joined

Jun 16, 2001

Location

St Louis

• Nov 5, 2014

• #13

DaveKamp said:

Hmmm... my bet, is that it was probably compromised before you bought it... if not, I'll second JST's suggestion that the starting circuit didn't disengage properly. That's certainly smoked...

Click to expand...

Putting that together with the following, there seems to be confusion....

John.t.little1 said:

I wired it exactly how the instructions stated and there was no relays in the motor it was just 8 caps 4 start 4 run.

Click to expand...

if true, there really is a problem.... what disconnects the start capacitors?

 

John.t.little1

Aluminum

Joined

Oct 10, 2014

Location

St. Augustine, FL

• Nov 5, 2014

• #14

I will look at the caps in the morning the caps were Inclosed in a riveted case. But I popped the lid to test a few. Idk if it's 4/4 but logic made me ASSume it.

 

JST

Diamond

Joined

Jun 16, 2001

Location

St Louis

• Nov 5, 2014

• #15

It's perfectly possible that the caps do double duty.

I have an Arco RPC, with one capacitor for run/start. The rotor has dual "windings", thin copper on top, and fat aluminum buried. The top winding works on start, and has higher resistance, giving good start torque (lots of phase shift).

The higher inductance buried "windings" take over when the slip frequency gets low enough, and provide a low slip operation. That makes it start easily, so the run cap can operate as a start cap, without the high slip normal with a high resistance rotor.

If yours uses a similar system, it might use only one cap , made up of the 8 you see, paralleled. If so, it might be good to check to see the caps are not shorted....... Shorted start caps might easily cause a problem such as you have.