Machine breakdown
1)Previously, the machine condition is ok but after our 3 phase induction motor problem we replaced it. the problem is the ammeter to show the value if motor start up is not going up. this machine use 2 induction motors 3 phase. only one motor will show the value at ammeter. I suspect the current transformer problem so I swap it then the value going up. But after I buy new current transformer and change it still have the same problem. the worst case 2 motors not showing any value ammeter when the motors turn ON.I already try to change other phase but it can on 1st try but after that still same problem. Can anyone help me?? Thank you.

 

Are the motors performing OK? just the ammeter not working?
Do you have any details on the current transformer/meter etc?
Max.

 

Yes,the motor performing ok only the ammeter.I am using MH current tranformer with ratio 60/5A,class 3 and burden 5VA. The ammeter also with same rating.

 

Do you have a blown or faulty meter maybe?
A current transformer and meter is a pretty simple basic device, not alot to go wrong.!
Max.

 

I think not,because yesterday already try it and it can work. For your information,this is new machine and still not send to our client. Previously,the motor problem because of 'humming'sound so we send to the manufacturer.

 

If new components then I would look at the correct selection or quality?
Especially if motor appears to work correctly, can you confirm with clamp-on test meter?
Max.

 

yeah also test it with clamp meter. the value shows 6.5 A.

 

you can refer attached picture

 

Did you try using more primary turns of the motor conductor around the C.T.?
http://www.electronics-tutorials.ws/transformer/current-transformer.html
Max.

 

can you explain how to make it?? and what are the effect after that??

 

You change the ratio of the CT by adding either primary turns of the motor conductor or the secondary.
Wind a turn of the motor conductor as shown.
Max.

 

Ok thank you Max.. I try it first..

 

Dear Max,

I already solve the problem. Not because of CT but wrong selection of core size wire. Before this I use only 0.5mm but total length quite far so I change it to 2.5mm. so ammeter working fine right now. Anyway thank you for your help and info.