Product Description:

The 21BRX701-J42AA resolver belongs to the Dynapar Resolvers series from Danaher. As a brushless electromagnetic transducer, it supplies absolute shaft-angle data to motion controllers and drive amplifiers so that servomotors can be commutated and positioned without the cumulative counting errors associated with incremental feedback. By integrating excitation and two sinusoidal pickup windings inside a compact frame, the unit provides rugged analog feedback for industrial automation systems where a digital encoder is not desired.

The resolver connects to the drive’s reference oscillator through its primary winding, which requires a sinusoidal carrier at 10 kHz. When energized at 7 Vrms, the primary winding draws approximately 40 mA. Under these conditions, the differential signal measured at electrical zero does not exceed 30 mV, supporting positional accuracy around the mechanical null. The output signals lag the reference by 5 degrees, so the controller must compensate for this phase shift during demodulation. With a transformation ratio of 0.50, each secondary winding delivers half the amplitude of the applied carrier. This ratio simplifies drive-side scaling while still generating a robust sine-cosine signal pair for resolver-to-digital conversion.

The aluminum housing measures 1.26 inches long and has an outer diameter of 2.1 inches. A 1.85-inch pilot centers the resolver body in a motor end bell, while the rotor has a 0.5-inch bore and extends 1.06 inches. The rotor operates with a resistance of 75 ohms, while the stator resistance reaches 120 ohms. Zero-sequence impedance is 214 ohms on the rotor side and 638 ohms on the stator side, limiting high-frequency leakage during carrier injection. The aluminum shell helps dissipate internally generated heat and protects the resolver windings. These electrical and physical properties support stable analog feedback during prolonged operating cycles without requiring optical sensing components.