Product Description:

The VAC3-D6 spindle drive is produced by Okuma within the VAC Spindle Drives series. It converts incoming DC bus energy into controlled three-phase output for high-speed machine-tool spindles, allowing accurate acceleration, braking, and constant-speed cutting under numerically controlled commands. The unit forms part of Okuma’s closed-loop CNC architecture, where the spindle drive, motor, and feedback circuits work together to maintain commanded surface speeds and torque profiles during milling, turning, or grinding cycles. Because spindle load can change quickly during tool entry, exit, and dwell, the drive must respond smoothly to changing torque demand without disturbing the programmed machining process.

It protects internal circuits with auxiliary fuses rated at 0.5 A on positions F3R, F3S, and F3T, while the main incoming lines are safeguarded by 5 A links on F1R, F1S, F2R, and F2S. An optical interface carries enabling and fault signals to the CNC, reducing the chance of ground-loop problems that can occur with electrical couplers. The power stage uses 2 IGBTs for pulse-width modulation and 1 diode for freewheeling current return. Thermal energy from these semiconductors is removed by a dedicated heat-sink fan, and one fan maintains airflow across the radiator fins. The F2T position is left without a fuse, so the associated low-voltage circuit is bypassed. This arrangement separates control signaling from the noisy power section and helps the inverter operate steadily during rapid spindle speed changes.

Energy storage and line conditioning are supplied by 3 capacitors that smooth the DC link and by 3 choke coils that attenuate ripple and limit inrush. By reducing bus ripple and moderating current surges, these passive components help deliver steadier power to the spindle motor during acceleration and heavy cutting. Positional feedback interlocks are reinforced through 2 magnet switches that monitor enclosure status before the inverter can be enabled. The drive partners with spindle motors whose 30-minute and continuous ratings reach 7.5/5.5 kW, providing reserve output for rapid metal removal while staying within thermal limits. The enclosure-monitoring circuit adds a straightforward permissive check before the power stage is allowed to run.