Studying the Qur'an for new reverts - when is wudu necessary?

[Little_Lion]

I know that Allah, in His grace and wisdom, tells us that we should only read the Qur'an in a state of cleanliness. However, I have heard several recommendations that people carry a small Qur'an with them, especially as they are learning it, so that they may study at any time: on the bus, between classes, any time they have a few minutes they can open it. However, it is next to impossible to remain clean as is proper throughout the day, without wudu every time you have a spare moment to study!

What are the requirements for those just learning the Qur'an? Are "student Qur'ans", those with translations and explanations, exempt from the cleanliness rule (obviously we should still treat them with the utmost respect - I carry mine in a padded slipcover) in some or any way? I have heard if the Arabic consists of less than 1/3 of the overall text, that it does not count as a Qur'an for cleanliness; is this true? And if we use digital versions instead of paper, what does that entail?

Jazak'Allah khayr to everyone for your consideration in this matter.