Hi Sargent york:
really appreciate your reply,
yes I believe the motor is a RAM motor,
one of my customers in Vietnam has five YK chillers in their plant, all the five chillers are equiped with RAM motor, just in 8 years, they have 3 motors burned,
and on the job site I currently work, there are another two same type chillers, their motor current also fluctuates, but no so serious, only have 2 or 3% differentials,
I am not sure if I can give advice to the customer to replace the motor, because the motor had been working well for years, it seems the quality of RAM motor is so bad that it will eventually has problem someday.
Have you done any leak testing on this Chiller ? if so have you fixed any problem areas ? , as mentioned before have you removed the charge ? if so how much did you get out in weight ? , because I believe you are short refrigerant.
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when I was working in Vietnam, my colleagues have removed the refrigerant out of the chiller, the weight is estimated 500Kgs.
we have done all the work you mentioned, the vacuum reading is 2000micron and it keeps the same after 24 hours.
yes the chiller is short of about 100-120 Kgs R134a, and I am going to make the deficiency later.
I have talked to the operators, they told me when the current fluctuation just occurred, the chiller was still running in good condition, so I don't think the shortage of refrigerant is the cause, but still I will make up the deficiency first.
Taicool, I understand your concern about advising a customer to replace a working motor. However, look at Klove's mention of a variac. That is an electrical tool or meter that is used to test a motor for an open rotor. Others on this site can probably provide you with info in how to perform this test. But I would first address other issues (low charge?) first. Trying to troubleshoot multiple problems is much easier and more accurate when done one at a time. And why not start with most obvious/easiest first?
Are you absolutely certain that you don't have a loose vane or two that may be opening and closing erratically?
I agree with you,
I will charge refrigerant first, then proceed to other moves,
about the variac, can you provide more information of it?
I have check every vane,
I manually open the vanes, then shake them by hand,
they all secured well.
The "Variac" test the wisened KLove referred to is extremely easy on your version of the YK. I believe you have an EM starter with the six motor leads coming out at the bottom. Simply obtain a "Variac" from a electronic/electrical supplier, secure the power to the chiller, "Verify" all power has been secured, then connect the variac to any of the 3 motor windings (1-4, 2-5, 3-6) and apply up to 5 amps current monitored with a analog clamp-on ammeter and at the same time open the coupling cover and rotate the shaft "Slowly" while monitoring the applied current. A deviation in the applied current will prove an open rotor bar, or bars. The SB from Trane has you seriesing any of the 2 windings but I have "Never" had to resort to this on a motor the size you are dealing with as the Variac cannot supply the voltage/current (5-amps) needed.
No need to remove refrigerant or undo the coupling, the test can be performed in less than 30 minutes on the Yorks...Much longer on any of the hermetics. The last Trane CVHF I was involved with had 13 open rotor bars. Verified with magnetic paper at the local motor shop.
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I got it, that kind of instrument is easy to get in electronis shop, thanks for your explanation and instruction.
also thanks Klove for providing the test method.
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Ain't "None" of us as smart as "All" of us..
It's best if you push the current up to 10 amps instead of 4.5 like the bulletin suggest. Best way is to have an on-line analysis test done. It will tell you for sure if you have a bad rotor. The variac test sometimes will lie to you because the mass is not spinning. I have seen several have broke rotor bars that when cool, the will have continuity but hot, they pull apart. You might also look at it through vibration analysis. If you know the number of bars, you can check aceleration at "bar pass frequency". Yes, RAM motors are "value engineered!"
Originally Posted by RichardL
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Sorry some mistake,
The motor is actually a Toshiba motor,
577Hp, FLA 776Amps, Ins Class F, S.F 1.0, LRA 5326 Amps,
I plan to do the test with variac first, for the on-line analysis test, I have to ask a professional motor shop to help, because I don't have those related appliances and knoeledge,
one more question, can you kindly suggest the proper specification of variac to be used in this kind of motor?