X-ray generators Flashcards
What is the purpose of an electrical transformer?
To change the voltage of a current?
How do electrical transformers work?
There are two coils with a different number of twists/ turns in each.
A current is run through one of the coils. The current running through the coil generates a changing magnetic field.
This changing magnetic field generates a current in the other wire.
The relative voltage of the currents is proportional to how many twists/ turns there are in the coils.
What is the first law of transformers?
Secondary voltage (output) is related to primary voltage (input) by the ratio of the number of turns (N) on the coils.
What is the second law of transformers
Product of voltage and current in the two circuits must be equal
What is the problems with using alternating current for x-ray generation?
- It’s only positive half the time (so it only generates x-rays half the time)
- It’s negative half the time (can cause damage to stuff)
- it varies a lot in it’s intensity
What device lets through only the positive part of an alternating current?
What device reverses the negative part of an alternating current?
(to make the whole thing positive)
What is fluctuation in the electrical output of current called?
How is ripple calculate
difference between max and minimum voltage reached (out of max voltage)
What is the waveform of an alternating current that’s been modulated by a rectifier called?
a half-wave rectified waveform
What is the waveform of an alternating current that’s been modulated by a ‘bridge rectifier’ called?
a full-wave rectified waveform
What device reduces the ripple of a full rectified waveform current further?
a three phase generator
how does a three phase generator work?
each current is out of sync with the others by 1/3 of a cycle (120 degrees).
The currents are added so that the minimum voltage never gets that low (but the maximum doesn’t increase at all)
What is a high-frequency inverter generator?
a new device that lowers ripple, it’s complicated how it works.
Rectifies current to be a had wave rectified current
Smooths the current to be pretty similar to direct current
Uses inverter to turn into a very high frequency alternating current
rectified this current to be a very high frequency positive only current
Then smooths this current to be a pretty low ripple current
How much ripple would you expect on a three phase, 6-pulse or medium frequency inverter?