CT ratio setting on energy meter

Status
Not open for further replies.

bobdxcool

Member level 5 Current Transfomer (CT) ratio setting on energy meter

I am using a smart energy meter which allows me to set the CT ratio among other parameters. I am using 50/5 ratio AC CT's. For the meter to do the kwh calculation correctly, I believe I have to set primary CT ratio to 50 and secondary CT ratio to 5. Now, if I have two rounds of the same 120 volt wire passing through the same CT, then I would set secondary ratio to 100. My question is, will this be equivalent to have just one round of wire through the CT and the primary ratio set to 50 , i.e the kwh calculated by the meter will still be right and I would'nt have to do any manipulations on the values obtained from the meter.

Last edited:

FvM

Super Moderator
Staff member Now, if I have two rounds of the same 120 volt wire passing through the same CT, then I would set secondary ratio to 100.
No, you get range of 25 A with two primary turns.

bobdxcool

Member level 5 No, you get range of 25 A with two primary turns.

Can you please explain more clearly ?

schmitt trigger The explanation is in the name: Ratio.

Ratio of primary turns vs secondary turns. Since CTs are usually a single primary turn, a 50:5 =10 current ratio means that the secondary must be 10 turns to maintain the same ratio. or 10:1, in the number of turns.

If now you put two turns in the primary while keeping the same 10 secondary turns, your new ratio will be 10:2 = 5; half of what you used to have.

The transformation ratio will change accordingly, such that to obtain 5 amps secondary, your primary can only be 25 amps.

Basic transformer equations. Remember the current transformation ratio is the reciprocal of the turns ratio.

Status
Not open for further replies.