amiruddin Posted May 29, 2007 Report Share Posted May 29, 2007 hi i want to know how to calculate overload setting for motor AC hi if the AC motor have 55 KW,how we can calculate for overload setting Link to comment Share on other sites More sharing options...
marke Posted May 30, 2007 Report Share Posted May 30, 2007 Hello amiruddin You set the overload relay setting to the same as the rated current of the motor. Best regards, Mark Empson | administratorSkype Contact = markempson | phone +64 274 363 067LMPForum | Power Factor | L M Photonics Ltd | Empson family | Advanced Motor Control Ltd | Pressure Transducers | Smart Relay | GSM Control | Mark Empson Website | AuCom | Soft Starters Link to comment Share on other sites More sharing options...
rene4538 Posted June 29, 2007 Report Share Posted June 29, 2007 hi i want to know how to calculate overload setting for motor AC hi if the AC motor have 55 KW,how we can calculate for overload setting You can also calculate using the this formula P=I.E ,p=power ,I=current ,E=volatge then you can get the approximate motor current rating.Correct me if i am wrong. best regards Link to comment Share on other sites More sharing options...
marke Posted June 29, 2007 Report Share Posted June 29, 2007 Hello rene4538 You have not taken into account the power factor or the efficiency which can have a major influence. P = V x I x eff x pf The power rating of the motor is the shaft power, not the electrical power. The best way to determine the current rating, is to look at the motor name plate. - always shows the current rating. Best regards, Mark Empson | administratorSkype Contact = markempson | phone +64 274 363 067LMPForum | Power Factor | L M Photonics Ltd | Empson family | Advanced Motor Control Ltd | Pressure Transducers | Smart Relay | GSM Control | Mark Empson Website | AuCom | Soft Starters Link to comment Share on other sites More sharing options...
AB2005 Posted June 30, 2007 Report Share Posted June 30, 2007 Normally, motors are selected 120% greater power than load. So, first, we check how much motor draws the current at the maximum working speed of machine which should be lesser than motor’s maximum current typed on the name plate. Now you can set the overload slightly at higher current under the motor full load current. This will also save your motor and your load. "Don't assume any thing, always check/ask and clear yourself". Link to comment Share on other sites More sharing options...
Nitin Posted June 30, 2007 Report Share Posted June 30, 2007 hi i want to know how to calculate overload setting for motor AC hi if the AC motor have 55 KW,how we can calculate for overload setting hi first U measure current with clampon meter and then increase relay setting 5 amp more than that. Link to comment Share on other sites More sharing options...
chaterpilar Posted September 5, 2007 Report Share Posted September 5, 2007 Dear Amirudin, The more the data you will give in the question the more closer the answer will be. For example 55 kw, at what what voltage 380 volts, 415 volts, 690 volts..? Let us say it is a 415 volts rated motor. In case of a star-delta starter the location of overload relay matters a lot, it can be located where 100% of current is passing through the relay or 58%is passing through. For sake of calculation, if the motor name plate rating is 100 amps, then follow these steps. 1. Set the relay at 58 amps and start the motor and 2.Check the current at the output of relay with a clampon meter after the motor is running at its full speed and full load. 3.Let us say it is 43 amps, then set relay 3amps above 43 that is 46 amps. A properly designed motor should have OLr setting at 80% of its full load current ( @ Name plate ) Hope it helps. Good Luck !! Chaterpilar Link to comment Share on other sites More sharing options...
pelia Posted September 13, 2007 Report Share Posted September 13, 2007 hi i want to know how to calculate overload setting for motor AC hi if the AC motor have 55 KW,how we can calculate for overload setting for the overload setting 1 a) 125% of the full load current rating of a motor having a marked service factor of 1.15 or greater 115% of the full load current rating of the motor which does not having a marked service factor or where the service factor is less than 1.15 2 where a motor overload device is so connected that it does not carry the total current designated on the motor name plate , such as for wye-delta starting , the percentage of the motor nameplate crrent applying to the selection or setting of the overload swhall be clearly marked on the motor starter shown in the motor starter manufacturs overload selection table Link to comment Share on other sites More sharing options...
SNSwamy Posted February 11, 2008 Report Share Posted February 11, 2008 hi i want to know how to calculate overload setting for motor AC hi if the AC motor have 55 KW,how we can calculate for overload setting find the actual running of the motor Check the voltage.depending on the load set the relay to that load if it is less than full load & if the load is more than full load set the relay at full load of motor Link to comment Share on other sites More sharing options...
Bysikmode Posted April 20, 2014 Report Share Posted April 20, 2014 thanks for the info guys. it'll really help me. dubli Link to comment Share on other sites More sharing options...
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