I searched shields, (nothing useful came back), and reads the shield generator mechanics entry and it left me with a couple of questions.
1. Is there any reason why you wouldn't just keep your shields raised all the time?
2. This may be a bug I was designing an Alpha shield plain jane, regeneration rate 1, 10 hs so the strength modifier is 100% and the shield strength is 10. However when I reduce the size to 1, this problem exists with any size reduction, according the size drop down selection the strength modifier is 31. 6% which jibes with the explanation in Steve's shield generator mechanics entry. If I understand this correctly then the shield strength should now be 3, rounding down to an even number, instead the shield strength is shown as 0.
If anyone knows whether this is a bug let me know and I will repost this in the bug report thread.