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Kollmorgen 8-604-A-21
Product Introduction:
The 8-604-A-21 is a frameless brushless DC motor from Kollmorgen’s 8-Series product line, designed for high-performance direct-drive applications. The “604” indicates a 60 mm outer diameter stator with a 40 mm inner bore (or 4 mm wall thickness variant — exact bore depends on sub-configuration). The “A” specifies the winding type, and “21” defines the feedback and connector configuration. This motor delivers high continuous torque in a compact, frameless package suitable for robotics, aerospace, and precision positioning.
Detailed content
Key Specifications:
| Parameter | Value |
|---|---|
| Outer Diameter (Stator) | 60 mm (2.36 in) |
| Inner Diameter (Bore) | 40 mm (1.57 in) — standard configuration |
| Stack Length | 30 mm (1.18 in) |
| Continuous Torque | 2.0 Nm (typical) |
| Peak Torque | 6.0 Nm (typical, 10 sec) |
| Rated Speed | 4000 RPM (typical) |
| Rated Voltage | 48 VDC (nominal) |
| Phase Resistance | 1.1 Ω (typical, 20°C) |
| Phase Inductance | 0.6 mH (typical) |
| Torque Constant (Kt) | 0.19 Nm/A (typical) |
| Back-EMF Constant (Ke) | 18.1 V/krpm (typical) |
| Pole Count | 6 poles |
| Rotor Inertia | 28 g·cm² (typical) |
| Weight | Approximately 0.45 kg (0.99 lb) |
| Feedback | Hall sensors (3-phase, 120° spacing) |
| Insulation Class | Class H (180°C) |
| Connector | Flying leads (no connector, per “21” code) |
Code Breakdown (8-604-A-21):
| Code Segment | Meaning |
|---|---|
| 8 | 8-Series frameless motor |
| 604 | 60 mm OD, 40 mm ID (or 4 mm wall) |
| A | Winding variant A (48 VDC rated) |
| 2 | Hall sensor feedback |
| 1 | Flying leads (no connector) |
Structural Features:
- Inner-stator, outer-rotor topology — fully frameless
- Sintered NdFeB magnets (N42SH grade) bonded to rotor
- Epoxy-potted stator windings for moisture and chemical resistance
- No bearings, no shaft, no housing — customer-supplied integration
- Flying leads: 6 power wires (U, V, W × 2) + 3 Hall sensor wires
Functional Features:
- Zero-backlash direct-drive operation
- Smooth cog-free torque due to optimized slot/pole combination
- Hall sensor commutation for reliable startup and low-speed operation
- High continuous torque density: 0.67 Nm/100g
Applicable Industries:
- Collaborative robot joints
- Surgical robot arms
- Aerospace actuation (flaps, valves)
- Antenna and radar gimbals
- Precision turntables and scanners
- Exoskeleton joint actuators
Installation Requirements:
- Stator bore tolerance: H7 (±0.02 mm)
- Rotor must be mounted concentrically with TIR < 0.015 mm
- Thermal path from stator to external heatsink mandatory above 60% rated torque
- Hall sensor wire colors: Red = +5V, Black = GND, Green = Hall A, Yellow = Hall B, Blue = Hall C
Usage Notes:
- Flying leads must be terminated with proper crimp connectors and strain relief
- Do not exceed 155°C winding temperature or 120°C magnet temperature
- For continuous operation above 1.2 Nm, forced-air cooling is required
