When you first enter into the Plasma Frigate, head down. You should see an entrance leading to the lower floor. From there, you go to the left and keep on going down until you see the third doorway. Go inside; you should see two rows of tables on each side. Between the tables on the right side is the Electrizer / Magmarizer.
If this is too difficult to follow, just watch this video; you can skip to 1:02 (that's when he enters into the Plasma Frigate.
Hope I helped!
Source: Experience , Above link