In an accelerator which applies an electrostatic field, accelerating energy is limited by applied voltage. The voltage cannot be increased without limit due to the potential electrical discharge. With a synchrotron, however, the higher accelerating energy can be obtained by spinning charged particles and applying an accelerating electric field at the right timing of the particles passing through and thereby accelerating charged particles multiple times.

Since the bigger electromagnet is required to spin particles within a fixed orbit to produce higher energy, the energy level accelerated by synchrotron is determined by the size of electromagnet.