| Click to Post a New Message!
Page | | | | | | | [ 8 ] | | |
| | |
|
Generator set up ideas wanted
I am NOT an Electrical Engineer, but do have a reasonable understanding of them.
In an AC motor direction is controlled by the way the fields are energized, which in turn controls the order in which fields are created and collapsed. By reversing the order, you reverse the direction the motor spins.
So far so good, now, there is a second way to reverse a motor, a very dangerous way, that is to reverse the connections, ie, swap the hot for the neutral, this will also reverse the direction in which the fields build and collapse.
This is why I said there may have been a wiring fault in the location it was in previously. The only two ways to reverse a motor are to change the wiring, or the polarity, if you didn't change anything but the location of the compressor then the other wiring HAD to be different, ie, reversed polarity. That is why you can now ground the case without tripping the breaker.
Best of luck.
|
|
 Add Photo
Bookmarks: |
|
| |
|
Generator set up ideas wanted
You cannot change the direction of rotation on a single phase AC motor by reversing the line connections. That is, going from white/white and black/black to white/black and black/white for 120v motor or swaping the blacks on a 220v motor. You cannot swap one of the two blacks for a white on a 220v motor because it would only get 120v and would burn up the motor and if you grounded the now loose black it would be a short and blow the breaker. Now, if it is a DC motor reversing the line will work.
To change the direction of rotation in a single phase AC motor you must change the connections of the windings internally according to the chart on the side of the motor. If you are using a 3 phase motor then to change rotation you just swap any two wires of the three line connections.
A single phase 120v motor is running on one phase of a three phase system. A single phase 220v motor is running on two phases of a three phase system. A three phase 220/440v motor is running on three phases of a three phase system.
All residential power systems today are 220v two phase systems. That is, you get two legs of the 3 phase grid. Most people don't know or understand that a 220v motor is running on two phases. I suspect that if you get leg one and two of a system at one location and then leg one and three at another then the motor that ran at the first location will run in reverse at the other location. I have no way to prove this but maybe the power company could tell me and maybe not. I just had an idea. I will take a single phase motor wired for 220v to my last employer and try this out as he has 3 phase in his machine shop and report back. That may explane why it switched direction from one place to another. Also, NO, the wiring was not faulty at any of the locations it was used. I do have experience wiring machine controls and home and business wiring.
|
|
Add Photo
Bookmarks: |
|
| |
|
Generator set up ideas wanted
You can not change direction of a single phase ac motor just by switching hot and neutral. The great majority of single phase motors are induction type motors. For most of these switching the leads for the start windings will reverse rotation. These are usually red and black, or they may be numbered 5 and 8.
|
|
Add Photo
Bookmarks: |
|
| |
|
Generator set up ideas wanted
I was thinking three phase, and that is what I was referring to, now that I re-read it I see it was a single phase motor, sorry for any confusion.
|
|
Add Photo
Bookmarks: |
|
| |
|
Generator set up ideas wanted
Carldarnell,
Consider yourself one fortunate soul ---
I tried to look up your serial # on the Smith motor but with no luck --- it's pretty old.
As you stated, in order to change the shaft rotational direction of an AC motor the field connection of the stator windings relative to the armature must be interchanged.
Having said that, I guess it is possible that older motors could have one side of the stator or armature tied to the frame. In that case it still should be possible to maintain the frame as the return while changing the rotational direction provided these operational details were understood.
With modern commercial motors there is no connection to the frame by design, (at least that I’m aware of).
Personally I'd get rid of the motor --- motors are pretty cheap these days. I personally wouldn't want a device with the frame tied to either the "hot" or "return" legs.
Secondly there is no "two" phase system in use in the US, (sin and cos with a phase shift of 90 deg).
Public power is either a 3 phase system, (120 deg) or a single phase transformer driven from one leg of the 3 phase system relative to the system neutral. The output of the transformer is typically 220 with a center tap --- but it is still single phase. Of course the output taps on either side of the center tap are 180 deg out of phase relative to each other --- think of your wall-wart.
I do hope your rethink your plan to use that motor. Just not worth the risk of potential injury in my opinion.
jdcman
|
|
Add Photo
Bookmarks: |
|
| |
|
Generator set up ideas wanted
I agree with jd's concern of the safety of using any motor (any electric anything for that mater with voltage where it can be touched) with voltage on the frame. Regardless of how safe a person is and how aware all it takes is one slip or stumble...it could be you, your child or someone who just stopped to say hello.
|
|
Add Photo
Bookmarks: |
|
| |
|
Generator set up ideas wanted
Generators and transfer switches. I talked to the lineman that works my area and hooked up my home and shop and instructed me how he wanted the meter base and disconnects. 400 amp service with 200anp in house and 200amp in shop with a 200amp disconnect on each branch. I asked about using a circuit breaker type disconnect as mentioned in an earlier post and he did not like the idea but if it meets code he would have to accept it. I have not asked if it meets code but I will probably use a standard transfer switch if and when I set up a stand by gen. As to breaking the neutral, he said at one time Ky Utilities wanted to do that but it never happened. He said they ground every pole and neutral at that pole. For it to cause a voltage feedback most or all of the grounds would have to break and the lineman would have to grab the open ends of a neutral line that has voltage on it. He said it would only happen if the lineman DID NOT FOLLOW CORRECT PROCEDURES.
|
|
Add Photo
Bookmarks: |
|
| |
|
Generator set up ideas wanted
I think this whole matter has been a little over-blown.
It is a safety issue, yes, but it's one of those odds game thing. It's a one in several millions type thing, but it IS a risk.
I prefer my odds at one in zero, I don't take unnecessary risks, period.
As a very old friend of the family, and lifelong hunting partner said to me one year when we spotted a bear ambling down the trail towards us "It's one black bear in ten thousand that will attack a human, and that is ONE bear, and I don't care what number he is.".
Best of luck.
|
|
Add Photo
Bookmarks: |
|
| |
|
Generator set up ideas wanted
That Damn compressor motor. I went to an A. O. Smith authorized repair shop and told him my problem. He checked with the factory for my motor and they have no info on it. I asked if I should bring it in to test. He asked is it running and I said yes. He asked is it grounded and I said yes. He said if it runs, makes no noise and is grounded it has no problem. When I got home I disconnected the ground and checked with a VOM. It read 14.7v. I reversed the rotation and checked the potential to ground and it read 21.7v. I touched the ground wire to the comp. during both readings and it did not kick the breaker. I wired it for the right direction and checked the ground and it showed a potential of 1.5v. What happened to the 14.7 I got the first time? Who knows and I don't care. Hooked up the ground and taped the leads and covered everything up. It runs, it's grounded, so what's the problem. It sure as hell won't shock anyone and it sure as hell runs. If it ever shorts out and blows the breaker I will have it rewired.
|
|
Add Photo
Bookmarks: |
|
| |
|
Generator set up ideas wanted
Carl,
To me it seems as if your ground is doing it's job.
To Murf, is Barrelpoint where you are posting the rest of the bear story? Some of us want to know if the bear ate either of you, don't leave us in suspense! PS: How does that 1 in 10,000 bear know that he/she is it? Makes one wonder. I wonder who counted those 10,000 bears to come up with that. Guess that stopped with 10,000 huh?
kt
|
|
Add Photo
Bookmarks: |
|
| |
|
Page | | | | | | | [ 8 ] | | |
Thread 120490 Filter by Poster:
2 | 13 | 1 | 2 | 10 | 4 | 2 | 9 | 1 | 3 | 13 | 1 | 20 | 2 | 1 | 2 | 1 | 1 | 1 |
|
()
Picture of the Day
DennisCTB
Unanswered Questions
Active Subjects
Hot Topics
Featured Suppliers
|
Gas Generator Weather Protecti
12-20-2005, 08:31 
Pics
Reply
Digg It 
Del.icio.us 
