A06B-6079-H203 Fanuc Servo Amplifier Module A06B6079H203 A06B-6079-H203

Fanuc A06B-6079-H203 | Alpha Servo Amplifier Module — SVM2-20/20, Dual-Axis, 283–325V / 2.5kW, 5.9A per Axis, Type A/B PWM Interface

Overview

The Fanuc A06B-6079-H203 is a dual-axis alpha series servo amplifier module, designated SVM2-20/20, delivering 5.9A rated continuous output on each of its L and M axis channels from a 2.5kW DC bus input.

It sits above the SVM2-12/12 in the alpha two-axis module hierarchy, offering roughly double the per-channel current capacity while maintaining the same compact 60mm module width.

This current step makes the SVM2-20/20 appropriate for machine axes driving mid-range alpha motors — specifically the αM2.5/3000, α3/2000, and αC6/2000 classes — where the higher torque output of these motors draws more continuous current than the 3.0A envelope of the smaller SVM2-12/12 can sustain.

The 60mm physical width is notable for a 5.9A per-axis module.

This compactness is achieved through 50A IPM (Intelligent Power Module) devices — each IPM integrates the six IGBT transistors, gate drivers, and internal protection circuits of one output stage into a single package.

At 5.9A rated continuous output, the 50A-class IPM provides substantial peak current headroom above the continuous rating, enabling the module to handle the acceleration transients of α3-class motors without approaching the IPM's protection limits.

Two such IPM modules in the 60mm package provide independent L and M axis output stages with no shared components in the output path — a fault in one channel's motor does not degrade the current regulation quality of the other.

Key Specifications

SVM2-20/20 Motor Pairing — α3 and αC6 Applications

The three motor designations compatible with the SVM2-20/20 span the mid-range of Fanuc's alpha servo motor family. The αM2.5/3000 is a compact motor with a rated torque of 2.5N·m at its rated 3000rpm — appropriate for lighter machine axes that still exceed the α2/3000 capability.

The α3/2000 provides 3N·m continuous torque at 2000rpm, suited to medium-duty axis drives where moderate torque at machining speeds is the dominant design requirement.

The αC6/2000 is a Cs-axis-specific motor configuration: a compact motor variant designed for the spindle Cs axis function on turning centres, where it drives workpiece rotation at low speeds for contouring or polygon turning in servo control mode.

This range of applications — conventional CNC machining centre axis drives, EDM electrode positioning, and turning centre Cs axis drives — explains why the SVM2-20/20 is found across a variety of machine types despite being a middle-of-the-range dual-axis module.

Any application where two axes need between 3.0A and 5.9A continuous drive current finds the SVM2-20/20 a correct and efficient specification.

Dual-Axis Efficiency in 60mm

The SVM2-20/20's ability to deliver 5.9A per axis from a 60mm-wide module reflects the efficiency gains of Fanuc's IPM technology integration compared to earlier discrete-component drive designs.

Both axis channels are managed by the single control card (A20B-2001-0931), which processes the CNC's PWM commands for both L and M axes simultaneously and generates independent gate drive signals for each IPM module. 

The wiring board (A16B-2202-0752) routes signals between the CNC interface connectors, the control card, and the two IPM output stages, and carries the absolute encoder battery connection (CX5) for both axes.

In a three-axis machine, one SVM2-20/20 handles two axes within 60mm, with a separate SVM1-20 or SVM1-12 handling the third axis.

Total rail space for three axes at this current class: 120mm (SVM2-20/20) + 60mm (SVM1) = 180mm, compared to 180mm for three individual SVM1-20 modules — the same total in this case, but the SVM2 reduces the number of DC bus connection points and CNC interface cable runs.

FAQ

Q1: What alpha motor class does the SVM2-20/20 drive, and what is the step above it?

The SVM2-20/20 at 5.9A per axis is sized for the αM2.5, α3, and αC6 motor range — Fanuc's mid-class alpha motors.

The next larger dual-axis module in the A06B-6079 series is the SVM2-12/40 (A06B-6079-H204) with 5.9A on L and 9.4A on M, covering a mixed configuration where the two axes have different motor sizes. The SVM2-40/40 (H206) at 12.5A per axis handles the next tier of heavier motors.

The SVM2-20/20 is selected when both axes carry motors of equal and moderate current demand.

Q2: The module uses Type A/B interface — what determines which mode is used on a given machine?

The CNC control series fitted to the machine determines the interface type. Fanuc Series 0-C, 15A, 16A, 18A, and 21A use Type A; Series 0-MD, 0-MF, 15B, 16B, 18B, and 21B use Type B. The interface mode is set on the module via a configuration jumper or switch on the wiring board.

When replacing an SVM2-20/20 on an existing machine, set the replacement module's interface to match the original. Incorrect interface configuration produces VRDY OFF alarms or CNC-to-drive communication errors immediately on power-up.

Q3: Can the SVM2-20/20 replace the SVM2-12/12 (A06B-6079-H201) if the H201 is unavailable?

Yes, in most cases. The SVM2-20/20 provides higher current per axis than the SVM2-12/12 (5.9A vs 3.0A), which does not harm smaller motors — the module simply operates at a fraction of its capacity.

The servo parameters must be set for the actual motor models on each axis; the larger module does not alter the motor's operating characteristics.

The only consideration is that the SVM2-20/20 draws slightly more DC bus current (2.5kW vs 1.5kW input), which is relevant only if the PSM is marginal for the installation.

Q4: The SVM2-20/20 is rated at 2.5kW input — how does this relate to PSM selection?

PSM selection sums the rated input powers of all SVM and SPM modules in the stack. The SVM2-20/20 contributes 2.5kW to this total. In a machine with one SVM2-20/20 covering X and Y axes (2.5kW) and a single SVM1-20 for Z (1.25kW) plus an SPM-5.5 spindle (5.5kW), the total is 9.25kW — exceeding the PSM-5.5's 6.8kW capacity and requiring at least a PSM-11 (13.8kW). The SVM2-20/20's 2.5kW demand is modest enough that it rarely determines the minimum PSM size in a full machine configuration.

Q5: What alarm codes on the A06B-6079-H203 indicate a channel-specific fault?

Alarm 8 on the module's 7-segment LED indicates L-axis overcurrent (HCL); Alarm 9 indicates M-axis overcurrent (HCM).

These channel-specific codes — plus the axis identification in the CNC's SV-4xx alarm — allow the maintenance engineer to determine which motor, motor cable, or output stage channel is at fault before removing the module.

As with all alpha SVM modules, the standard diagnostic sequence is to disconnect the suspect motor's U/V/W cables and test motor insulation resistance (several hundred megaohms to protective earth is acceptable) before concluding the module requires replacement.