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3 phase reversing swith problems

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Forum topic by Jerry posted 188 days ago 408 views 0 times favorited 14 replies Add to Favorites Watch
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Jerry

1963 posts in 2052 days


188 days ago

Not sure just how many have any knowledge on this issue but never know til I ask. I recently bought a 7.5 hp 3 phase shaper at an auction. All was great, shaper is super quiet and runs smooth. So I was just excited. So today, I go to run a panel and realized the spindle is spinning in the wrong direction. The switch appears to have a reverse but the reverse is dead. It does cause something to go click on the inside. I took the switch apart and on the forward side I get power to all 3 terminals, on the reverse side it appears I only get 110 to on terminal, no power to the second terminal and just 15 volts to the third terminal. So I assume the switch is my issue however I am not even sure where to get a replacement switch.

I appreciate the help from anyone. Worst case scenario will be to hire an electrician or remove the switch and bring it to my motor guy who deals in everything motor/switch. That is probably my best option. I called one electrician who told me most motors only go in one direction, I figured that was my sign to look elsewhere.

-- Jerry Nettrour, San Antonio, www.topqualitycabinets.net


14 replies so far

View JustJoe's profile

JustJoe

1554 posts in 543 days


#1 posted 188 days ago

I don’t have real 3-phase, but I’ve got VFDs creating it. They have 3 hots coming off the VFD providing 3-phase power to the motor. If I switch any two of those three wires it will reverse the motor direction. If you’ve got three wires coming in to yours, you might try switching two of the wires with each other. That won’t fix your reverse switch, but it might get your motor turning in the direction you want it to.

-- This Ad Space For Sale! Your Ad Here! Reach a targeted audience! Affordable Rates, easy financing! Contact an ad represenative today at JustJoe's Advertising Consortium.

View Jerry's profile

Jerry

1963 posts in 2052 days


#2 posted 188 days ago

I think I will try and do that JustJoe. I did not think of that. It does not make sense to me that much because all 3 hots are bringing in 120v, seems to make them all pretty much equal. Good idea though.

-- Jerry Nettrour, San Antonio, www.topqualitycabinets.net

View Loren's profile

Loren

6774 posts in 2153 days


#3 posted 188 days ago

Switch two of the hot wire positions on the plug. That should
change the direction. The plug is just the easiest place to
do it.

View Jerry's profile

Jerry

1963 posts in 2052 days


#4 posted 188 days ago

Loren, if it is that simple then I will be very happy. Thanks. I will do that first thing in the morning.

-- Jerry Nettrour, San Antonio, www.topqualitycabinets.net

View Grandpa's profile

Grandpa

2985 posts in 1180 days


#5 posted 188 days ago

typically 3 phase is the simplest thing to reverse. Maybe that is how it got to where you are now…..LOL This should be an easy fix for you. Loren has it right but it might mess you up if you move the machine to another location and an electrician looks at the wiring…..not sure. It is something you can do.

View GOOD LUCK TO ALL's profile

GOOD LUCK TO ALL

418 posts in 232 days


#6 posted 188 days ago

I have 4- 3 phase tools. I just moved into a new shop and as luck would have it, 3 out of 4 ran backwards.
Swapped 2 wires around and viola. I have a 30 and 60 amp disconnect boxes, that is where I switched the wires.
EDIT: I switched the wires of one at the plug receptacle.
I’m no electrician and couldn’t tell you why, it doesn’t make sense to me. All 3 hots are carrying the same volts, I couldn’t figure why it changes. Hoping some electrician pops in and explains it.

View Loren's profile

Loren

6774 posts in 2153 days


#7 posted 188 days ago

This article explains a bit…

http://wiki.vintagemachinery.org/Three%20Phase%20Frequently%20Asked%20Questions.ashx

I think because there are 3 hots you have the juice at 120
degree positions around the motor, so reversing the sequence
of two of them causes the motor to turn the other way…
cycles and hertz and stuff, operating out-of-phase,
meaning not at the same time. So it’s sort of like you
have 3 electromagnets placed at 120 degree intervals
around the motor shaft and they pulse on and off
x 60 hertz, which makes for 180 pulses per second
in a repeating pattern which pulls the motor around in
one direction of the other.

This is why they don’t need capacitors to get started
in the correct direction too. If you’ve fussed with a motor
with a failing capacitor, you may have noticed you
can spin it and it will start going in the way you spun it.
Having the pulse points at 180 degrees means the
direction cannot be controlled by the sequencing of
hot wires.

I’m no electrician and don’t really understand it
probably but this is my sort of mental model of
how 3 phase motors work. I welcome correction
of course. Based on this understanding I’ve assembled
a phase converter, programmed a VFD and got four
3 phase machines going.

View Jerry's profile

Jerry

1963 posts in 2052 days


#8 posted 188 days ago

Awesome guys. I am fairly sure I have my answer. Now I am anxious to get back to the shop tomorrow to start playing with the shaper again. Thanks for the info and the article.

-- Jerry Nettrour, San Antonio, www.topqualitycabinets.net

View TopamaxSurvivor's profile

TopamaxSurvivor

14416 posts in 2181 days


#9 posted 188 days ago

KevinJeffery, It depends on whether or not the turbine at the dam is going the way you want your motor to go or not. If it isn’t, swap any 2 and your motor will be going the way you want to go. Hope that clears it up a little.

-- "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View TopamaxSurvivor's profile

TopamaxSurvivor

14416 posts in 2181 days


#10 posted 188 days ago

Jerry, My guess is somebody in the past probably switched instantly to reverse and burned out the contacts on one direction of your switch. When you reverse the wiring, you will have one direction. 3 phase motors can be instantly reversed for plug stopping, ect, but it takes some seriously over-sized contacts to do the job ;-)

-- "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View GOOD LUCK TO ALL's profile

GOOD LUCK TO ALL

418 posts in 232 days


#11 posted 188 days ago

Thanks Topamax,
Now all I have to do is put in a call to the Dam operators and have them switch the turbines into reverse….
But wait, won’t that pull all the water out of the river and over fill the lake??
It’s a vicious circle. lol

View Jerry's profile

Jerry

1963 posts in 2052 days


#12 posted 188 days ago

Great input guys.

-- Jerry Nettrour, San Antonio, www.topqualitycabinets.net

View TopamaxSurvivor's profile

TopamaxSurvivor

14416 posts in 2181 days


#13 posted 188 days ago

That could cause the damn to break if the water ran uphill long enough ;-) That is why we usually swap the wires.

-- "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View Bluepine38's profile

Bluepine38

2876 posts in 1590 days


#14 posted 187 days ago

Delta used to make a wonderful shaper that normally came with a 5 hp motor that would handle most
industrial work, but offered the 7.5 as an option, is that what you have, and did you get the power feeder
with it?

-- As ever, Gus-the 75 yr young apprentice carpenter

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