The high temperature superconducting (HTS) dynamic synchronous condenser (DSC) is characterized by low impedance and fast response, and has superior reactive power compensation performance compared with conventional regulators. In order to study the topology and electromagnetic relationship in HTS DSC, this paper analyzes the electromagnetic design of a 50 Mvar HTS DSC. The excitation coil is made of 1 mm diameter MgB 2 wire and is run through a helium gas line cooled to 20 K to produce an air gap flux density of 1.4 T. The magnetic induction intensity distribution under different excitation conditions is calculated by finite element simulation. The maximum magnetic inductance is calculated to be 3.0 T and 3.7 T for no-load and 3.5 times strong excitation conditions, respectively. The no-load electric potential and the stator winding voltage and current under different excitation conditions are obtained, and the design of the screen is presented. In addition, the reactive power compensation characteristics of the superconducting synchronous regulator are analyzed to obtain the excitation current and reactive power magnitude of the regulator under the under excitation and over excitation conditions.