Problem starting refrigerator motor

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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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-doctor-book/boosting-your-split-phase-120-volt-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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
--
Phil Scott
Ideas are bullet proof.
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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.

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 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
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Hi Ben!

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.

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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.