Question about Vol.2 Polyphase AC circuits

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Joined Nov 6, 2012

I have been reading through the Polyphase AC circuits section in Vol.2. Near the end of a lesson, two examples are given where a Wye source is feeding a Delta and Wye load network. One of the windings in the Wye source fails, and it is then shown that two of the three loads in both the Wye and Delta load network have their voltage halved. I was just wondering what circuit analysis can be done to come to this conclusion as I am having a hard time understaning how the two loads have their voltages halved. I do understand the third load being either zero or 208.

Similarly, the worksheet for the lesson has a similar problem (Question 9) in which the winding on the source of a Y-Y network fails. It is then stated that two of the resistors will operate at 86.7% of their capacity. I was also wondering how this number was derived. Thanks for your help.