Product Description:

The B-204-B-21-S is a permanent-magnet, brushless servo motor built by Kollmorgen for the Goldline B and BH Motors series. Designed for closed-loop motion axes, the unit converts drive current into precise torque for automated pick-and-place heads, index tables, and packaging spindles. Kollmorgen integrates the stator windings, resolver feedback, and a liquid-resistant housing to provide a compact actuator that connects directly to Servostar drives in industrial automation lines.

The motor generates a back electromotive force of 51.2 VRMS/kRPM, which the drive uses to set field-oriented control parameters. Terminal impedance includes a phase resistance of 2.48 ohms and a phase inductance of 38.0 mH, so current loops must account for relatively high energy storage and moderate copper loss. The windings accept up to 250 V RMS of line voltage, permitting operation on standard 230-volt industrial supplies while leaving margin for regenerative transients. The rotor has 4 magnetic poles, establishing the electrical frequency relationship between the drive and mechanical speed.

Mechanical and thermal performance includes a continuous stall torque of 4.47 N-m at 40 °C and a rotor inertia of 0.0001729 kg-m², providing a balance between load acceleration and positional stability. The motor weighs 6.2 kg and fits a standard metric rear-extension mount. It uses a bayonet connector, but mating plugs are not included. An IP67 rating, supported by a Viton shaft seal, allows washdown cleaning and protects internal laminations from coolant ingress. Static friction is 0.10 N-m, and viscous damping is 0.009 N-m/kRPM, so low-speed oscillations remain minimal. Thermal resistance is 0.73 °C/W, indicating how quickly heat leaves the frame under continuous duty. The electromagnetic torque constant of 0.85 N-m/A RMS allows current demand to be calculated during acceleration and helps with selecting a drive that has adequate peak output.