A transformer upgrade can be used to upgrade a machine's power input rate or tier. Place one or two transformer upgrades into the four right-most slots to upgrade a machine.
One upgrade enables a tier 1 machine to receive 128EU/t. Two upgrades enables it to receive 512EU/t, three for 2048 EU/t, and four for more than that. It will also allow the use of higher tier portable storage items like the Energy Crystal.
Important: Make sure to put the transformer upgrade into the machine before applying power. Temporarily removing the wiring while setting up your machines is a good way to do this.
See: Crafting Guide