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Home > Archive > Electrical Engineering > May 2006 > Problem starting refrigerator motor
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Problem starting refrigerator motor
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| Hello!
I have a problem starting a scratch refrigerator motor. I plan to use
it for an air compressor.
The problem is:
The motor had some components attached to it, but they were burnt.
Directly to the motor there were 3 pins, so I supposed it was a three
phase motor. Then, I bought a starter capacitor, supposing it was the
way to run a three phase motor using one phase. I didn't know tre
required capacitance, so I bought the first capacitor I found, and it
was a 6 uF, 400VAC.
The motor doesn't start this way, and I know the motor is OK. Later,
searching at the web, I found several ways to start a 3-phase motor,
using some relay that plugs the capacitance only at start. I only
remember from the original components attached to the motor that it had
a plastic enclosure with something like a thick round button-cell
battery. I assumed it was a capacitor, but the one I bought doesn't
seem like that one at all, the new one is the typical cilinder 4 inches
tall.
Maybe I need another start technique?
Can I use any start technique I wish on every motor? Or is the kind of
motor associated with the start device?
In case I can use a capacitor, which capacitance should I use for a
typical refrigerator motor???
Thanks in advance!
Eduardo
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| Ben Miller 2006-05-10, 11:21 am |
| "Edu" <edugimeno@hotmail.com> wrote in message
news:1147260582.230259.270240@j73g2000cwa.googlegroups.com...
> Hello!
>
> I have a problem starting a scratch refrigerator motor. I plan to use
> it for an air compressor.
> The problem is:
> The motor had some components attached to it, but they were burnt.
> Directly to the motor there were 3 pins, so I supposed it was a three
> phase motor. Then, I bought a starter capacitor, supposing it was the
> way to run a three phase motor using one phase. I didn't know tre
> required capacitance, so I bought the first capacitor I found, and it
> was a 6 uF, 400VAC.
>
> The motor doesn't start this way, and I know the motor is OK. Later,
> searching at the web, I found several ways to start a 3-phase motor,
> using some relay that plugs the capacitance only at start. I only
> remember from the original components attached to the motor that it had
> a plastic enclosure with something like a thick round button-cell
> battery. I assumed it was a capacitor, but the one I bought doesn't
> seem like that one at all, the new one is the typical cilinder 4 inches
> tall.
>
> Maybe I need another start technique?
> Can I use any start technique I wish on every motor? Or is the kind of
> motor associated with the start device?
> In case I can use a capacitor, which capacitance should I use for a
> typical refrigerator motor???
>
> Thanks in advance!
> Eduardo
>
It is a single-phase motor that requires specific starting components...
capacitor and relay. You need to look up the correct parts for that model
compressor. Also, be aware that refrigeration compressors rely on
refrigerant flow over the motor winding for cooling, and they are designed
to pump oil (which is held inside the shell) with the vapor. While you will
get some air, it isn't the best air compressor, and it may not last long!
Ben Miller
--
Benjamin D. Miller, PE
B. MILLER ENGINEERING
www.bmillerengineering.com
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| Ben Miller 2006-05-10, 11:21 am |
| I forgot to mention that the "button cell" sounds like the overload
protector, which you will also need to replace woith the correct device.
ALso, the design voltage and phase should be marked on a nameplate on the
compressor.
Ben Miller
--
Benjamin D. Miller, PE
B. MILLER ENGINEERING
www.bmillerengineering.com
"Ben Miller" <benmiller@worldnet.att.net> wrote in message
news:hZSdnc0Uvdxgc_zZ4p2dnA@comcast.com...
> "Edu" <edugimeno@hotmail.com> wrote in message
> news:1147260582.230259.270240@j73g2000cwa.googlegroups.com...
>
> It is a single-phase motor that requires specific starting components...
> capacitor and relay. You need to look up the correct parts for that model
> compressor. Also, be aware that refrigeration compressors rely on
> refrigerant flow over the motor winding for cooling, and they are designed
> to pump oil (which is held inside the shell) with the vapor. While you
> will get some air, it isn't the best air compressor, and it may not last
> long!
>
> Ben Miller
>
> --
> Benjamin D. Miller, PE
> B. MILLER ENGINEERING
> www.bmillerengineering.com
>
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| Hello Ben.
Thanks for the reply!
Some comments:
1.-I pretend to make a low cost air compressor. If I have to buy
original parts, it won't be a low cost design...:-)
2.-If you suppose the button-cell-like part was a overload protector,
then there was no condenser, because the rest of the parts in the
plastic enclosure attached were only relay-like contacts.
3.-There are several web pages explaining how to make a low cost air
compressor with a refrigerator motor, and they seem to work. Also a
friend of mine showed one of these to me some years ago, and it worked.
I only need to use a decanter to make sure the liquid doens't reach the
air exit.
I will try to find the burnt parts that I extracted from the motor in
the thrash bin this weekend, and see if there is some nameplate in the
compressor.
Thanks for your time!
Eduardo
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| Hello again.
Searching the web, I found that the pins under the plastic enclosure I
discarded were in this disposition:
http://fridgedoctor.com/figures/fig5-32w.gif
In this webpage
(http://www.fridgedoctor.com/fridge-...compressor.html)
they talk about these compressors as having a common pin, a run pin,
and a start pin. Correct me if i'm wrong but I think I can do the
following test:
1.-With the ohm-meter determine which pin is which
2.-Plug 220v neutral-phase into common-run pins
3.-Temporarily apply phase to start for a while and unplug it as soon
as it starts.
Would it be a way to check it? Later I should try to locate some start
relay to use in place of this test, right?
Thanks!
Eduardo
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| Ben Miller 2006-05-10, 1:21 pm |
| "Edu" <edugimeno@hotmail.com> wrote in message
news:1147271636.671141.276920@j73g2000cwa.googlegroups.com...
> Thanks for the reply!
> Some comments:
> 1.-I pretend to make a low cost air compressor. If I have to buy
> original parts, it won't be a low cost design...:-)
That was sort of my point. By the time you get done messing around, there
are some inexpensive air compressors that might be as cost effective, and
more reliable.
> 2.-If you suppose the button-cell-like part was a overload protector,
> then there was no condenser, because the rest of the parts in the
> plastic enclosure attached were only relay-like contacts.
Some compressor motors do not use a capacitor, or it is sometimes mounted
elsewhere within the refrigerator. Some use both a run and start cap, others
only one or the other.
> 3.-There are several web pages explaining how to make a low cost air
> compressor with a refrigerator motor, and they seem to work. Also a
> friend of mine showed one of these to me some years ago, and it worked.
> I only need to use a decanter to make sure the liquid doens't reach the
I agree that people do it. However, I have worked with these compressors for
many years in their intended application, and they are very unforgiving of
operating conditions outside of their design envelope. It is not the way to
go for a serious, reliable air compressor, but if you are just
experimenting, have fun!
Ben Miller
--
Benjamin D. Miller, PE
B. MILLER ENGINEERING
www.bmillerengineering.com
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| Hi Ben!
>Some compressor motors do not use a capacitor, or it is sometimes mounted
>elsewhere within the refrigerator. Some use both a run and start cap, others
>only one or the other.
I'm pretty sure there wasn't any other part outside the compressor and
the relay enclosure. So I assume all the stuff I found in the plastic
enclosure was a relay and a overload protection.
I will try to get another relay from scratch.
>I agree that people do it. However, I have worked with these compressors for
>many years in their intended application, and they are very unforgiving of
>operating conditions outside of their design envelope. It is not the way to
>go for a serious, reliable air compressor, but if you are just
>experimenting, have fun!
You are right. I'm just experimenting. Actually, I don't have anything
to do with the air compressor, just build it because I found 2 working
refrigerator compressors, and if in the future it can help me with
something, good!
Thanks for your time!
Regards.
Eduardo.
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| Phil Scott 2006-05-12, 6:21 pm |
|
--
Phil Scott
Ideas are bullet proof.
"Edu" <edugimeno@hotmail.com> wrote in message
news:1147272754.100388.33630@e56g2000cwe.googlegroups.com...
> Hello again.
>
> Searching the web, I found that the pins under the plastic
> enclosure I
> discarded were in this disposition:
> http://fridgedoctor.com/figures/fig5-32w.gif
> In this webpage
> (http://www.fridgedoctor.com/fridge-...compressor.html)
> they talk about these compressors as having a common pin, a
> run pin,
> and a start pin. Correct me if i'm wrong but I think I can
> do the
> following test:
>
> 1.-With the ohm-meter determine which pin is which
> 2.-Plug 220v neutral-phase into common-run pins
> 3.-Temporarily apply phase to start for a while and unplug
> it as soon
> as it starts.
Im in the business.
If its a 110vac rated compressor use 110vac only.
Its single phase not three phase.
Ohm reads...
....the highest read will be between the Run and Start
terminals.
The next highest read will be between the common and start
terminal. the lowest read will be between the common and run
terminal.
Buy a start kit for it at any appliance parts house... thats a
current relay and capacitor. $25 dollars or so.
Don't try to test it manually because you need a start
capacitor in the circuit (see a diagram) and those can explode
or shock you badly if you are not careful.
To find a start kit for that compressor..you will need the HP,
voltage and model number... a kit for a similar sized
compressor will probably work, especially if the HP or
amperage ratings are the same.
If you use it for an air compressor you will need an oil
separator of some type.. in the air line.
Phil Scott
>
> Would it be a way to check it? Later I should try to locate
> some start
> relay to use in place of this test, right?
>
> Thanks!
> Eduardo
>
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| Thanks everyone for the replies.
I finally started it manually. I determined each pin by measuring with
ohmeter, plugged Common/Run directly to neutral/phase 220v, and
attached phase for 1 second to Start and then released. It started
blowing perfectly and remained working for all the time I had it
connected.
The I bought a "standard start relay for refrigerator compressors", at
the price of 19 euro, and now I have to guess how to attach it. There
are two coupled parts. I dissasembled one and it contained just a coin
shape piece of metal. I suppose it is an overload fuse Only 2 real pins
to outside, and 2 more redundant. The other part is sealed, and has 3
wires. I suppose they are input, output for run, and output for start.
All of them have almost-zero-ohm reading with each other.
This weekend I will try to test-and error guess the pinout.
Thanks!
Best regrads.
Eduardo.
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| New problems with my firdge compressor...
The problem is that the start relay I bought blowed my compressor. I
have another one to test, but I cannot fail this time.
The relay looks like this:
http://uploadjar.com/uploads/relay.jpg
The part at the left has a ceramic disc inside. I suppose an overload
protector. Two pins are connected to one side, and 2 to the other.
There is a spare hole connected to pin 1 of the relay expecting to be
jumpered to some side of the disc.
The other part (the relay I suppose) has 3 pins. It is a black plastic
sealed cilindric box. It has almost-0 ohm between every pair of pins.
This is what I tested:
Applied 220v to one side of the fuse, jumpered the other side to pin 1
of relay, wired pin 2 to "start" of compressor, and pin 3 to "run" of
compressor. Wired neutral from 220v to common of compressor. The
compressor started well, but the fuse heated after 1 minute and
stopped. So i bypassed the fuse, and sweeped run/start wires.
Compressor started again, but after 1 minute, the start winding blowed.
It blowed smoke through the oulet, and the resistance of the start pin
became infinite. The compressor is in the thrash now.
I have another one to check, it is the same model. But this time I
cannot fail.
Any idea to avoid risks?
Thanks in advance.
Eduardo
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