3 phase amp reading

[Lab_rat]

Guys, wondering if you can help me? Having had a quick read through I think I am in the right place!

We are having to service an unit and need to get readings. Our electrician is in hospital and we merely need a few readings using a clamp meter. I have worked along side this guy for years and told the boss I can get the readings (more fool me).

Anyway I have got all the voltage reading, current reading when the motor first starts (its a delta motor) and current readings once the machine is running under normal conditions.

However it goes into other more indepth running tests, thats the bit I normally do. Making sure the mechanical side is sound. But at each stage it just says amperage reading? The sparky has only put in 1 reading? How can this be when it is 3 phase? Is it an 'average' of the 3? Just puzzled as to how I can get only 1 amp reading!

Incidently the machine was serviced only 5 weeks ago but its our policy that it is checked again before it leaves the workshops/stores. Its amazing how much the readings can change. But so can the mechanical side due to temperature etc..

Thanks in advance guys. By the way quite an impressive site by the way! Loads of info

 

[Evans Electric]

On 3 phase all the readings would be the same, you could try each one.

Did you mean it is Star-Delta ? in which case the start-up readings (Star) will be much higher than the run ( Delta) take the Delta readings.

Hope this helps.

Deke

 

[Andy™]

If its balanced (which motors are, but the control gear may give slightly different readings), then all 3 phases will draw the same current

 

[Lab_rat]

They are all around the same reading. But not exact. So basically I just take the average reading then? Or leave it hooked up to one phase and use that?

Yes we have to have start up readings and running under various stress conditions etc but as well as 3 phase amp readings there is a box on the rear sheet for only 1 amp reading. Looking at the old sheets none of the single readings match any of the phase readings at the times taken. Blushing

 

[Andy™]

just use one reading

 

[Lab_rat]

Thanks bud LOL the spark will be glad we never called anybody in, he is paranoid about losing his job while he is in hospital ...... but may wind him up a little

 

[elvis]

They should all be pretty much the same, if you are noticing a radical difference in one or all three readings then you should get the motor checked out...

Out of interest (I can be a bore) what is the motor running and what readings are you getting?

Should be big pats on the back for you from all round eh?