Voltage drop or excess controller

Circuit breakers you are refering cannot offer protection for high voltage..Pl let us know what voltage u are using.If you are using single phase from RYB and Nuetral ,check nuetral connection.It may be getting disconnected resulting in overvolatages in one of the phase and undervoltage in another phase.

We are using 3-phase 380-400V AC 50Hz. Any solution please.....

You might consider some form of votage compensation and using the compressor on a constant run basis, not stopping and starting it but using a pressure relief valve to bleed off excess pressure. This removes the problem of high starting inrush current which, when compounded by low voltage, can cause conditions approaching locked rotor currents.

Try a VSD or a soft start unit.

If I understand you correctly, your mains voltage is of very poor quality/reliability. In that case,you need Undervoltage protection (a relay or circuit breaker that switches off the power when the supply drops below a preset value). Make sure there is some form of timer to prevent turning on until the supply has been good for several minutes, or the relay may make things worse than they are!

Your CB's will not trip because they are current sensitive and do not depend on voltage regulation.Under large voltage drop, they will trip getting close to locked rotor situations, but this is a sever situation that if happens frequently needs serious consideration of preventive equipment, such as adjustable under voltage detectors. An over voltage situation will trip them due to increase in current drain. What you need, and this is not so expensive in your case (15KW), is a 3φ line conditioner which can take care of voltage variations as well as cosine φ corrections, for both capacitive or reactive loads. There are electronic or mechanical conditioners. Both are working well when correctly installed and calculated for the job.

Hope it helps

Wangito.

You need to watch the Load Amps over a 6 hr. period.

After that set the CB trip setting just above your observed max. Load Amps

If you still do not get overcurrent trip-

-well change that CB to another tested/certified and with variable setting

WORTH IT.

What power are you using? if maybe you are using single phase from RYB on supply, check your return neutral it may happen you have a loose connection.Bear in mind that you should consider a form of voltage compensation, using a compressor continuously and not stopping and starting, you must release some pressure. Protection: have u considered using a switchgear with 220v coil closing and opening fuses. I can design a circuit for you if you are interested. just send me all the compressor spec and explain exactly how you want it to operate!

well thanks for your comments. we are using 3-phase 380-400VAC 50Hz. compressors runs with an oxygen generator automatically with auto load and auto unload functions. sometimes we observe low voltage and sometimes sudden high voltage in 3-phase mains supply. what we want is to use any setup before the compressor and dryer+oxygen generator (these two runs on 220VAC) that is capable to safeguard the compressor in case high voltage or low voltage in mains 3-phase supply on any phase. So that in case of any miss-happening with the mains supply due to current or voltage the circuit trips and not the equipment be damaged. i hope you understand what i mean.

regds.

Go back and re-read posts 6 and 7!

Is there a motor protector with heaters in the compressor? Any significant over or under voltage to the compressor should cause enough current change to trip a motor protector. There are some solid state ones that are more sensitive than the heater style.

I would advise.. 1) Check the current/voltage over a period of 24 hours using a powermeter ( Kyoritsu make). 2) Install a UV/OV relay at the incomer of the panel (Schneider) part no RM4TR322 to shut off the compressor. another area is to check the ambient temperature of the room where the compressor is installed, compressors require a lot of ventilation and usually this is ignored causing higher ambient temperature....and the subsequent problems in connections. hope it helps.