The application of Resonant Magnetic Perturbations (RMP) to tokamaks recently gained a lot of attention due to the possibility of ELM suppression or mitigation. The iron core tokamak TEXTOR with circular plasma cross-section is specially suited to study the 3D effects of RMPs due to its Dynamic Ergodic Divertor (DED). The DED consists of 16 helically aligned perturbation coils installed in-vessel at the high-field side and can be operated in several base modes (m/n = 12/4, 6/2 and 3/1) with either DC or AC current supply. The addition of the RMP to an axisymmetric equilibrium perturbs the force balance.To re-establish the force balance, we recalculate the 3D equilibrium including an equilibrium response to the perturbation field. A full penetration of the RMP is assumed and screening of the RMP is not taken into account. The converged 3D equilibria are compared with the simple vacuum superposition assumption.