You need to get a factory Rep out there to check this.....There are many possibilities that could cause these failures, and you don't give a timeframe....

A few questions,

What capacity?

What refrigerant type?

Is the compressor failure from no oil? No cool suction gas? If this is a semi-hermetic this may be simple, if hermetic compressor you'll need to cut it open.

Is there compressor protection sized correctly for this motor capacity. Overload trip on locked rotor?

ignator

Sometimes, a bad start contact of the motor starter, leads to single phasing. The result will be regular failure of the motor.

Are all these compressors and motors identical? Are the normal electrical loads similar?

If so you have ready access to a bench mark for comparison. Find out what is different and you may find the problem.

Also explore Joshi's suggestion in #3

I would not have gone through 4 motors before I took some action straight after the first burn out I would have made the following tests to check the system

1 Have you done a test to check the voltage supplied on all 3 phases at the motor while under load?

2 Have you monitored the current drawn on all 3 phases of the motor that keeps failing?

Unless the motors keep getting water in the windings or you are using an undersized motor there is basically only 2 other things that will burn the motor out.

1 there is too much load on the motor because of a restriction or a faulty bearing etc in the compressor & the current measurement will tell you if it is higher than the rating on the tag.If this is the case why didn't the overload/ fuse blow ?

2 is the voltage on all 3 phases at the motor as it should be under full load? if not the motor controller or relevant circuitry supplying the motor could have a fault something like a burnt contact or even a burnt terminal, fuse terminal or isolating switch. You can work your way back through the circuit from the motor checking the various items for damage.

Get those measurements & tell us what you find you might even answer your own question

There are many other causes for a scroll to burn out

-clogged suction strainer (you would be amazed at how many people dont even know they are there)

-spinning backwards

-inop condenser fan (causes higher discharge temps, higher suction temps, and can cause motor to overheat)

There really needs to be an in depth analysis of BOTH the refrigerant side and the electrical side. Any number of things can be wrong ............. get a pro to do the TS and then you might be able to take over from there

Excellent points across the board.

Install suction filters and liquid line filters.

If this is the primary compressor does it have the digital unloader in it and is the timing set up right. The digital unloaders have a tendency to pump out oil into the system if the separation cycles are longer than 15 seconds. the extended pump outs will also run hot and seize bearings and premature burnouts. Be sure that the systems has the oil recovery kit installed in the liquid line to ensure oil return to the suction.

Be sure to check system super heats to assure proper evaporator saturation and compressor cooling through the return suction.

Once the compressor has been replaced (following all good practice rules) then please carefully check the refrigerant charge, super-heat settings, compressor operating temperature, the electrical load across the phases and the voltage between the phases etc.

My experience in fault finding has taught me never to accept anything but check everything (thinking 'out of the box') and secondly. never assume! Lastly, never be afraid to ask (even what you may consider as being stupid questions) because this will not only assist you to solve the problem but also ensure your growth in knowledge!

Remember a quick repair is a production solution NOT a technical solution!

+1

Mr Yendamuri, my advise is to install a new compressor and perform a complete start up. You should document as a base line reference: Suction pressure and temperature, discharge pressure and temperature, oil level or net oil pressure if oil pump port fitting is available. Also take voltage and current readings while under load. With the system off take a mega ohm reading from every leg of the isolated compressor to the chassis ground of the compressor. Depending on the size of your compressor you may want to take a vibration reading as well. Suction pressure must be above its saturation pressure at the given suction temp or else your comp will try to pump liquid, wich will cause it to fail. Suction temp should not be higher than 80 Fahrenheit, since it is the sole method for cooling the windings in the motor. Discharge temp is most times a function of suction temp. For larger comps I wouldn't want a hot gas temp above 195 F. Since you probably use POE oil in yours oil breakdown may not occur as fast as with mineral oil but it will still happen at high discharge temps. High head pressure will increase the electrical load and discharge temp. A small voltage unbalance will cause a large current unbalance loading the motor windings unequally, however a faulty winding or other conditions can also cause phase unbalance. You may have a way to check the amount of oil in the comp crankcase, compare oil level in sight glass to OEM specs, if possible do a net oil pressure calculation and compare to specs. Low oil conditions cause as much damage as high oil, so take care in this step, also monitor the rate of oil return back to the comp, if the oil stays in the system is bad, if it all comes back suddenly it's horrible. Mega ohm and vibration readings will change overtime as the compressor wears, they will give you a trend you can follow to predict failure if used properly. Cope land has a white paper on mega ohm readings and comp failure. Many conditions in the gas piping and valve system can cause any and all of the above mentioned conditions. Hope this helped.

I think it is high time for us to take a sabbatical, till the OP returns with feedback.

I don't know if this will help but contact this person:

Kevin Kibler

kkibler@mafindustries.com

He is in charge of our electrical department and we use Danfoss controllers quite a bit. We manufacture machinery used on produce packinghouses.

Tell him you were referred by Robert Karp, just put that in your subject line.

Prior to our analysis, we need to know the following:

1. Unit manufacuturer

2. Unit specs/nameplate

3. Air cooled or water cooled

4. single circuit or multiple circuits

Scroll compressor normally fail due to the following installation issue;

1. pipe sizing

2. short elbows should be used and avoid oil trap - especially if evaporator are located above or below the unit

3. after unit burn out or unit failure, system line should have been flush, clean and install suction strainer during start up.

Prior to our analysis, we need to know the following:

1. Unit manufacuturer : Hangzhon Shanli Purify Eqpt., China, Compressors: Danfoss, Performer Series

2. Unit specs/nameplate:

Compressor Details:

3. Air cooled or water cooled: Water Cooled

4. single circuit or multiple circuits: Twin Circuit

Scroll compressor normally fail due to the following installation issue;

1. pipe sizing

2. short elbows should be used and avoid oil trap - especially if evaporator are located above or below the unit

3. after unit burn out or unit failure, system line should have been flush, clean and install suction strainer during start up.

Your Message: Help

Hi! Thanks a lot. It's overwhelming to know that there's so much fraternity to share n take much care in answering or commenting.

We have taken the stock of the things and will be fitting back a refurbished compressor and I will be posting the latest on this as it happens.

Thank all of you once again

Yendamuri