Product Core Brief
- Model: LT304, OEM material number 0 608 750 085
- Brand: REXROTH (Bosch Rexroth LT30x EC motor power pack series)
- Series: LT30 compact integrated EC spindle servo power unit family
- Core Function: Convert stabilized DC intermediate bus voltage to variable-frequency three-phase AC to drive high-speed EC spindle motors with closed-loop speed and current regulation.
- Product Type: Vertical DIN rail mount servo power pack with passive convection cooling, built-in dual auxiliary logic voltage outputs
- Key Specs: 7 A continuous RMS motor output | 1600 VA rated power | 280–370 V DC intermediate bus | 0–667 Hz output frequency | Condition: Refurbished Load-Tested Surplus
- Unit marking note: Nameplate printed 330 V = nominal intermediate circuit voltage reference for cabinet design calculations.
Product Introduction
The REXROTH receives regulated DC bus power from VM310 cabinet power supplies and delivers high-frequency variable AC output to EC high-speed spindle motors for CNC machining and semiconductor cutting equipment. It integrates 24 V and 5 V auxiliary logic rails to power local sensor and encoder circuits without separate auxiliary converters.This unit differs from lower-current LT303 variants by supporting a 7 A continuous output and 20,000 RPM maximum spindle speed. OEM field data records its rated MTBF at 42,000 operating hours under 24/7 cyclic high-speed spindle loading at 40 °C cabinet ambient.
Key Technical Specifications
| Parameter | Value |
|---|---|
| Nominal intermediate DC circuit voltage | 330 V DC, operating range 280–370 V DC |
| Continuous RMS motor output current | 7 A |
| Short-duration peak overload current | 28 A (short transient acceleration duty only) |
| Rated continuous apparent power | 1600 VA |
| Adjustable output frequency range | 0 Hz to 667 Hz |
| Maximum mechanical spindle speed | 20,000 rpm |
| Auxiliary control supply outputs | +24 V DC for valve/encoder power; +5 V DC for processor logic |
| Max permitted motor cable length | 100 m shielded cable |
| Cooling system | Passive natural convection, no internal blower |
| Mechanical mounting | Standard 35 mm vertical DIN rail rack housing |
| Unit net weight | 2.7 kg (3.43 kg fully packaged shipping weight) |
| Enclosure protection rating | IP20 cabinet-only installation |
| Full rated operating ambient temp | 0 °C to +40 °C; linear performance derate above +40 °C up to 55 °C |
| Storage / transport temperature range | -20 °C to +70 °C, non-condensing 20–95 % RH |
| Integrated protection circuits | DC bus over/undervoltage lockout, output short-circuit, overcurrent cutback, thermal overtemperature shutdown, motor cable break detection |
| Compliance certifications | CE, UL, EN61000 Class A EMC filtering, SEMI S2 cleanroom processing equipment qualified |
Quality Control Process (Engineer’s Perspective)
- Incoming Verification: Cross-reference serial number against Rexroth OEM 0608750085 part database; inspect aluminum heat sink for dents, front terminal blocks for corrosion, and DC bus terminal lugs for oxidation. Photograph DC bus, motor power, and auxiliary I/O pin layout for field wiring reference.
- Live Functional Test: Mount unit to DIN rail test bench paired with high-speed EC spindle motor simulator; run 24 hour cyclic speed ramp profiles from 0–20,000 rpm. Use a Fluke 115 signal logger to track three-phase output current balance and auxiliary 24 V / 5 V voltage stability.
- Electrical Parameter Test: 500 V Megger insulation test between DC bus power stages and chassis ground (pass threshold >10 MΩ); verify output overcurrent protection triggers at 115 % of 7 A continuous rated load without permanent latch failure.
- Frequency & Aux Output Verification: Sweep output frequency across full 0–667 Hz range to confirm smooth speed regulation; validate no auxiliary voltage droop under full combined 24 V / 5 V logic load.
- Final QC & Packaging: Replace aged DC bus filter capacitors during refurbishment cycles; cap unused motor power and DC bus terminal ports with OEM plastic insulating plugs, seal unit in anti-static PE bag, apply dated QC Pass label listing frequency linearity, output current balance, and thermal shutdown trigger test metrics before foam-lined carton packing.
Replacement Pitfall Guide
❗ LT303 lower-current power packs cannot replace this unit on high-speed heavy-cut spindle axes. Underrated output stages trigger constant overcurrent faults during full spindle acceleration to 20,000 rpm. Always cross-check spindle motor continuous current draw before swapping modules.❗ DC Bus Voltage Wiring Tolerance Risk: The only accepts 280–370 V intermediate bus supply. Mismatched VM310 power supply jumper settings that push bus voltage above 370 V will activate permanent OVP lockout on power-up. Photograph original VM310 mains jumper configuration before removal.❗ Unshielded Motor Cable Interference Hazard: Unshielded spindle motor wiring run parallel to low-level 5 V logic cabling creates encoder signal noise and unstable spindle speed regulation. Separate motor power looms from auxiliary signal harnesses by a minimum 50 mm inside cabinet cable trays.❗ Passive Cooling Airflow Obstruction Risk: Cable bundles covering heat sink surface block natural convection cooling. Restricted heat dissipation triggers unplanned thermal shutdown during sustained 1600 VA full-load spindle operation. Maintain 50 mm unobstructed clearance on all heat sink sides.❗ ESD Aux Logic Circuit Damage: Onboard 5 V processor logic PCB traces carry low electrostatic tolerance. Always rest the unit on a grounded anti-static mat during terminal block rewiring, especially in low-humidity cleanroom production environments.Keep these in mind and you’ll cut 90% of rework time.
Compatibility Matrix & Benchmarks
Compatibility Matrix
- LT303 low-current spindle power pack → : Needs Adaptation — increase spindle acceleration limits in motion program to match 7 A continuous output capacity
- VM310 cabinet multi-channel power supply → : Direct — regulated 330 V nominal DC bus output natively matches module intermediate circuit voltage range
- CML40.2-SP-330-NA-NNNN-NW SERCOS motion PLC → : Direct — ±10 V analog spindle speed setpoint signals from CPU DAQ output operate the power pack without extra signal conditioning
- MSK compact servo motor series → : Incompatible — is designed exclusively for high-frequency EC spindle motors, not standard low-frequency servo synchronous motors
