If all the other charges in the universe are fixed, then mattashii is right.
The trick to undestand the Cyclotron is in the graphic: chttps://en.wikipedia.org/wiki/Cyclotron#/media/File:Cyclotro...
It has two semicircular parts A an B, that act like a big capacitor. The electrons travel in circles, sometime it's inside A and sometimes is in B.
If the voltage between A and B is constant, it accelerates and the decelerates and then accelerates and the decelerates and then accelerates and the decelerates and then ... that is quite boring.
The trick is that when it's inside A you make A negative and B positive, so it accelerates going from A to B. While the electron is inside B you switch the voltages and now B negative and A positive, so it accelerates going from B to A. Now, While the electron is inside A you switch the voltages and now A negative and B positive, so it accelerates going from A to B. ...
So the trick to gain energy in both directions is to change the voltages of the semicircular parts. This change cost energy, so there is no magic creation of energy.
Probably the article in Wikipedia explains it better.