In this paper we present a new theory, Modified Orbital Motion Limited - EMission, which examines the effect of electron emission on the charging of large dust grains. One of the most important aspects is the calculation of the particle's floating potential, which is the potential that the dust acquires when it is in contact with the plasma. Our theory determines the floating potential on the surface of the dust grain and predicts the formation of a potential well. Our model is applied in the Dust in TOKamakS (DTOKS) dust transport code and it is compared with DTOKS' pre-existing model.