component to limit inrush current in a transformer

Thread Starter

strantor

Joined Oct 3, 2010
5,369
did you have a look at the link I posted? ;)

I can't remember it very well, because it's been a while, but I did a test on exactly this phenomen, and as far as I remember I was surprised seeing a bigger inrush current when the transformer was connected at zero voltage. Maybe someone should test this again...
hint well taken. I've been reading all your comments but I won't have any useful feedback until later. this just dropped down on my supervisor-written list of priorities. I tried hooking my clampmeter to the oscope as I mentioned but I seem to have a problem with my clamp meter - it's not reading current - big problem for a clamp meter. I am going to send it off for repair.
 

THE_RB

Joined Feb 11, 2008
5,438
did you have a look at the link I posted? ;)

I can't remember it very well, because it's been a while, but I did a test on exactly this phenomen, and as far as I remember I was surprised seeing a bigger inrush current when the transformer was connected at zero voltage. Maybe someone should test this again...
There will be NO inrush current when the transformer is connected at the zero cross point, because there is no voltage. The inrush current occurs AFTER the zero cross point. :)
 

praondevou

Joined Jul 9, 2011
2,942
There will be NO inrush current when the transformer is connected at the zero cross point, because there is no voltage. The inrush current occurs AFTER the zero cross point. :)
Ok, ok, of course I didn't mean there was a bigger inrush current at the exact moment (zero crossing) where the transformer was connected.

Just to make it clear: the inrush current that appears AFTER you apply AC voltage at zero crossing is bigger than the inrush current you'd have if you applied AC voltage at its peak value. :D:D
 
Like somebody said early-er on, just change the supply breaker to a D-class breaker or motor control breaker which will allow the great startup current to happen before it trips, it is standard practise in motor control circuits.
 

Thread Starter

strantor

Joined Oct 3, 2010
5,369
Like somebody said early-er on, just change the supply breaker to a D-class breaker or motor control breaker which will allow the great startup current to happen before it trips, it is standard practise in motor control circuits.
Did somebody already say that? I must have missed it. that's a good idea; but how would I size the elements? that's usually from a chart of motor HP.
 
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