This paper describes the characteristics of the magnetic systems of active magnetic radial bearings that are combined with permanent magnets to provide bias force and electromagnets to supply control force. The permanent magnets are placed between two ring-shaped stators, and share their pole-legs with those of the electromagnets. The stator and rotor cores are made of silicon steel strips. Incremental magnetic fluxes with fixed working airgap are detected with search coils near the pole leg faces. Their frequency characteristics are obtained to sinusoidal input to the power amplifier of electromagnet. The experimental results are compared with the numerical result based on a model using identified parameters.