A dynamic model for a medium-voltage vacuum circuit breaker is constructed using the ADAMS software. The model is used to investigate the mechanical characteristics of the circuit breaker under the influence of electrodynamic forces. The characteristics are also investigated experimentally. The simulated and experimental results are in close agreement. It is shown that electrodynamic force increases the breaking speed of the moving contacts by 0.2m/s. The model can be used to highlight design criteria for the optimal operation of medium-voltage circuit breakers.