Magnitising Inrush Current in Transformers

i expect you mean magnetising inrush current in transformers

Try this link : Magnetising inrush current

Yes, this inrush magnetizing current is really very high even in small pulse transformers. Perhaps a fast peak detector circuit attached to CT can easily catch its peak value.

think of it like a hot air balloon. it takes in warmed air and developes lift as it is fill while at the same time it leaks some air to allow warmer air to replace it. it takes a greater amount for the initial fill to establish your magentic field and there is very little resistance at the start. it is intersting to watch the output of the secondary when the power is removed and the field collapses.

You may want to check out this thread where the transformer inrush current has been debated, along with other high-inrush loads.

http://cr4.globalspec.com/thread/55660

By a simple definiton it is initial current which flows into a transformer at the event of switching on. This is because of initial low resistance and zero back EMF plus current required for intitial flux build up. This is one of the reasons that overcurrent devices are kept time lagged.

How much time lag between resistive current flow to inductive flux build up in transformer primary circuit? When current is increasing, does this mean flux is still sleeping.

Inductance by definition suppose to oppose current flow and faster is the change or higher if the frequency greater is the inductance effect. At what frequency this is not holding good and any definition for it?

The quantam of inrush current is directly proportional to the KVA/MVA of the transforemer. The frequency to be ofcourse 50/60cs, because for high or ultra high fequencies transformer used are of negligible sizes. For example Mig-7 aircraft engine is started in workshops on 500cs frequency at 110 volts and the transformer used is only 3 KVA. The inrush current can be calculated for individual transforme as per its size and construction.

Any protection engineer can calculate the time delay factor precisely.