  We consider the overdamped motion of Brownian particles, interacting via
particle exclusion, in an external potential that varies with time and space.
We show that periodic potentials that maintain specific position-dependent
phase relations generate time-averaged directed current of particles. We obtain
analytic results for a lattice version of the model using a recently developed
perturbative approach. Many interesting features like particle-hole symmetry,
current reversal with changing density, and system-size dependence of current
are obtained. We propose possible experiments to test our predictions.
