In these drives the input energy from a fixed frequency AC source (the AC mains power supply) is converted to a DC form by means of a rectifier and stored in a energy storage element in the drive. The variable voltage (or current), variable frequency output is generated from this energy reservoir.n these drives the input energy from a fixed frequency AC source (the AC mains power supply) is converted to a DC form by means of a rectifier and stored in a energy storage element in the drive. The variable voltage (or current), variable frequency output is generated from this energy reservoir.
Recently I had the occasion to help a family member out with a domestic roundtrip ticket. Unlike the last time, our timing was pretty tight, and I found that because I was within 21 days of the flight, both United and American charge a $75 close-in booking fee. Delta does not charge such a fee, but of course you can never find any Saver award availability on Delta (this time was no exception).
Roundtrip is 135,000 United miles + $181.50 in fees, the revenue ticket is $16,201, and the miles foregone, since I'm not an elite member, are 4462. The nominal value would be (16201 - 181.5) / (135,000 + 4462) = 11.5 cents per mile.ost to Buy Miles. As we covered in How to Buy Ultimate Rewards Points, you can buy up to 5000 Ultimate Rewards points per month for $125, which equates to 2.5 cents per point = 2.5 cents per United mile, since Ultimate Rewards points transfer 1:1 to United miles.