Cunliffe Mill Electrical Problems

[Brain Coral]

Hello all,

First, I want to wish all of you a Happy New Year...

I started a thread about this horizontal mill here... http://www.hobby-machinist.com/showthread.php/23622-Cunliffe-Horizontal-Milling-Machine

... but decided to start a new thread here, concerning the electrical issues that I am having.

I recieved some replacement fuses from a kind friend in England over the Christmas holidays, to replace the 50 amp fuse that I burned out while trying to start the 2-speed motor on the mill.

Here are a few pics of the electrical panel to start with...

















Here's a pic of the mill...



This mill has a 2-speed motor, rated at 4hp (low speed) and 8hp (high speed). I have it powered with a 10hp RPC. I have no trouble at all in powering it at the low speed setting and can take a good cut with it. But when I try to power it up at high speed, the contactor cuts out. As well, I finally burnt out a 50amp fuse while trying to power it up at high speed after a few tries.

I have to go have lunch and will be back with more info...

Brian

 

[Brain Coral]

Back again...

There is a main power switch to the panel, that when engaged, locks the panel door closed...



So, once I recieved the new fuses and replaced the one that had burnt out, I decided to open the panel door (disconnected, of course... !!! ) and turn the switch to on with a couple of screw drivers, in order to see what went on upon turning the mill on.

When powering the mill up on the low speed (4hp) setting, the contactor to the right engages and stays engaged while the mill motor is running, and then drops back out once the stop button is pushed.

When attemting to power up the mill in the high speed setting (8hp) setting, the same contactor engages and then drops out on its own with a small puff of smoke coming from the contactor, shutting the motor down. The contactor on the left never engages at any time.

It was suggested that I try starting the mill at the low speed setting, and while it is still running, switch to the high speed setting. All this did, was the contactor let go and the motor shut back down.

I'm beginning to wonder if my 10hp RPC doesn't have quite enough juice to get the mill going at the 8hp setting. I have read recently, that if I have additional equipment of a lower hp running before I start the mill, it will boost the RPC's capacity. If this is true, how exactly is it done ?

At the present, I simply have a heavy gage wire and plug coming out of the RPC panel and a corresponding plug coming from the mill. I also have the same setup on my lathe, shaper, and vertical mill.

I found this link...

" If you have multiple pieces of equipment in your shop that are powered by three phase motors, all of the motors that are running at any one time will act as rotary phase converters, and will improve the quality of the power. Just wire them all including your idler through a single 3 phase sub panel, and power two legs of the sub panel with single phase 240 - the other leg will be powered by the phase converter and any other motors that you have idling. Breaker everything (including the idler) with the normal size breaker for the individual motors. Then if you have one piece of equipment that draws a lot of current, you can start your phase converter, and then start another motor and let it idle in addition to the phase converter, while you use the high draw equipment. Needless to say you need to address all safety implications of having multiple machines powered up at one time. "

Is this correct ? I have a lead on a 3-phase electrical panel for $100.00 with what appears to be several breakers. What should I be looking for in the way of the main breaker that feeds the panel ?

Brian

 

[Ulma Doctor]

Hi Brian,
there is a big blue wire behind the contactor on the right that appears to be broken.
or is that a figment of my imagination?

 

[Brain Coral]

Hi Brian,
there is a big blue wire behind the contactor on the right that appears to be broken.
or is that a figment of my imagination?

Hello Mike,

I just went down to have a look to be sure.... no, nothing is broken there...

About the 3-phase panel... does it work like the quote and will a 275amp panel work for me ?

 

[den-den]

About the 3-phase panel... does it work like the quote and will a 275amp panel work for me ?

Yes, running motors will help the RPC and smooth out some fluctuations.
275 amps sounds like a lot, but there are more things to a panel in addition to amp capacity
does it come with breakers?
Can you get breakers that fit it in sizes appropriate for your needs?
Does it have space for as many breakers as you need (plus a spare or two)?

I am not convinced that your problem with the high speed is related to your RPC capacity, although that may become a problem if you need the full 8hp of the mill. You should go through the wiring diagram and verify the controls work before assuming the problem is the RPC.

 

[Brain Coral]

Hello den-den,

Yes, the panel has lots of 3-phase breakers...

Unfortunately, I don't have a wiring diagram and really don't know where to begin to trouble-shoot it...

Brian

 

[Ulma Doctor]

Hello Mike,

I just went down to have a look to be sure.... no, nothing is broken there...

About the 3-phase panel... does it work like the quote and will a 275amp panel work for me ?

i saw a blue wire that was next to one of the contactor coils that looked suspicious , i'm glad it was only in my imagination.

the three phase panel idea is true, 275 would work out great! but it is overkill
by running more motors in the circuit, the total circuit balance is harder to distort.it becomes a better autotransformer
in other words- you short circuit a motor every time you fire it off, which distorts circuit balance- with a RPC you'll have 2 legs that are supplied and 1 leg that is generated through induction as long as single phase power is not interrupted to the RPC.
the RPC will supply 3 phases of power in relation to each other but the generated leg will not shoulder the load in the same manner as the legs connected to it's input. Added motors help smooth out the balance differences between all motors in the system.

 

[Ulma Doctor]

at this point i'm suspect of the speed selector switch & wiring.
i can't rule out the high speed motor windings at this point,
but as stated before with some effort we can get to the bottom of it!:detective:

 

[Brain Coral]

Hello Mike,

Thanks for the input. The holidays have been much busier than I would have imagined and there hasn't been much time for the shop. I do intend on moving the motor out of the base, to see how things are wired and will post pics and text as to what I find.

Would that be a good start, or should I start somewhere else first É

Oops... the darned shift and control keys are close to each other and when I hit them both in a certain way, I begin to speak Spanish...

Brian

 

[Ulma Doctor]

i think yanking the motor or at least gaining access to the leads for testing the windings would be a great start.
if we can isolate the motor and test the high speed windings, we can eliminate the motor as the cause.

as a side note, i can't rule out the possibility of the last owner not having the high speed switch wired correctly, but that will be another discussion.