while reading about sequence networks, I realized this. Suppose I apply same phase to the primary of Star-Delta transformer, say instead of applying A,B, and C phase to the three terminals, I mistakenly apply A,A and A phase to all the terminals, <Neutral is applied appropriately>. Then since the voltages applied comprises zero sequence voltage, it will also induce zero sequence voltage in the secondary, and since the delta loop provides path for zero sequence current, circulating currents should flow. My guess is, it should be devastating to the transformer. Am I right? Has anybody done this mistakenly? Thanks.