Subject: How does Lenz's Law explain the action of an aluminum ring levitator?

I've asked this question before and was refered to the archives in which I 
found no satisfactory answer.  This question refers to the apparatus in which 
an AC driven coil with an iron core levitates a closed aluminum ring.  
According to Lenz's law, an induced current in the ring will create field which 
opposes the change in the external field developed by the coil.  If the 
external field is increasing, the induced field will be in the opposite 
direction to oppose the increase in the external field.  This leads to a 
repulsive force which makes sense.  If the external field begins to decrease 
however, the induced field should oppose the change which would put it in the 
same direction as the external field which in turn should produce an attractive 
force.  This is not the case.  I would think that the external and induced 
fields would always be 90 degrees out of phase which would lead to equal 
amounts of attraction and repulsion.  What's really going on to produce a net 
repulsive force?

Re: How does Lenz's Law explain the action of an aluminum ring levitator?