FANUC A06B-6117-H304 Servo Amplifier Module — AiSV-20/20/40, Three-Axis Alpha i, 200V Platform

Three axes in a single module, with an asymmetric current layout. That design detail is the defining characteristic of the A06B-6117-H304, and understanding it is the fastest way to confirm you're ordering the right part.

The H304 is the largest three-axis drive in FANUC's 6117 Alpha i servo amplifier family. Designated SVM3-20/20/40i (AiSV-20/20/40), it drives three servo axes simultaneously from one compact unit — but unlike a symmetric three-axis module where all channels carry identical rated current, the H304 allocates its power unevenly: the L and M axes each rated at 6.5A, while the N axis carries 13A. That doubled N-axis rating has a practical logic, and it shapes where this module belongs in the machine.

Sande Electric stocks the A06B-6117-H304 in new and used (inspected) condition, with worldwide dispatch in 0–3 working days.

The 6117 Alpha i Platform: Where This Module Sits

The 6117 series represents FANUC's mainstream 200V Alpha i servo generation — the modular drive family that became the backbone of FANUC's CNC systems through the 0i-C/D and 30i/31i control generations. Unlike the earlier alpha series (6090, 6096) or the beta series (6130, 6132, 6134), the 6117 Alpha i lineup brought HRV2 and HRV3 current control algorithms, a slimmer 60mm module width with external heatsink architecture, and FSSB fiber optic communication as standard.

These modules are installed in a shared DC bus cabinet alongside an aiPS power supply module, which converts incoming 200V AC to the regulated DC bus. The H304's rated DC bus input is 283–325V DC at 9.5 kW total — that power budget feeds all three axes, and understanding it matters when you're sizing the power supply for your cabinet configuration.

Within the 6117 family, the module ranges from single-axis (H1xx), dual-axis (H2xx), to three-axis (H3xx). The H304 sits at the top of the three-axis range, differentiated from the H303 by its asymmetric axis current allocation.

Why the N-Axis Gets Double the Current

The SVM3-20/20/20i (H303) and SVM3-20/20/40i (H304) are both three-axis modules from the same family, and at first glance the H304 looks like an H303 with one upgraded channel. But the design choice reflects real axis-loading differences in CNC machining centers.

In a typical vertical machining center, the X and Y axes move the table and column in the horizontal plane — these are relatively light moves, even at speed, because gravity doesn't work against horizontal motion. The Z axis is different. It moves the spindle head or table vertically, directly opposing gravity, often while clamping against a heavy workpiece. Z-axis cuts involve higher cutting forces in the feed direction. The N axis — which on many machine configurations connects to the Z-axis or a similarly loaded primary axis — benefits from the additional 13A rated current capacity.

This is why replacing an H304 with an H303 is not straightforward: the N-axis motor on your machine was matched to the H304's 13A rated output. Running it from a 6.5A channel will cause the amplifier to fault on overcurrent under normal cutting conditions.

Technical Specifications

H303 vs H304: Clearing Up the Most Common Ordering Mistake

The two modules look nearly identical. Same series, same physical width, same FSSB interface, same cabinet fit. The number codes at the end of the part number are the only differentiator that matters:

A06B-6117-H303 = SVM3-20/20/20i — all three axes at 6.5A rated output. Used when all three axes on the machine have similar current requirements — often found on smaller machining centers or machines where Z-axis loading is not significantly heavier than X/Y.

A06B-6117-H304 = SVM3-20/20/40i — L and M axes at 6.5A, N axis at 13A. Used when the third axis carries heavier mechanical load and requires higher continuous current capability.

If your machine was originally fitted with an H304 and you fit an H303, the system may appear to initialize correctly but will fault on the N-axis under any meaningful cutting load. Conversely, fitting an H304 in place of an H303 is generally feasible from a hardware perspective if the aiPS power supply budget supports it — but this should always be confirmed against your machine's original electrical documentation before installation.

Condition Options

New units are genuine FANUC stock, unworn, backed by a 12-month warranty. For facilities where three-axis failure means complete machine downtime, a new unit eliminates service-history uncertainty.

Used (inspected) units carry a 3-month warranty and represent a practical stocking option for maintenance engineers who need a working spare on the shelf without the lead time of a new unit order. The 6117 is a mature platform — quality used units are generally reliable working spares.

Contact us to confirm current stock availability before ordering, as condition-specific availability fluctuates.

Ordering, Payment & Shipping

Worldwide dispatch via DHL and FedEx within 0–3 working days of confirmed payment. Combined shipping is available on multi-item orders.

Payment methods accepted:

• Bank Transfer (T/T) — all order values
• PayPal — orders up to $500
• Western Union — all order values

Import duties and local taxes are the buyer's responsibility. Contact us for a shipping cost estimate if you need one before checkout.

Warranty & Returns

Returns are accepted when units arrive damaged, incomplete, not as described, or prove non-functional within 4 days of receipt. The unit must be in original condition with the warranty label intact. Return shipping is at the buyer's cost. Failures resulting from incorrect wiring, mismatched axis motor connection, or physical damage post-delivery fall outside warranty coverage.

Frequently Asked Questions

Q1: The H304 has three axes — can one failed axis channel be isolated so the other two keep the machine running?

No. The A06B-6117-H304 is a single integrated module sharing one DC bus connection and one FSSB communication link with the CNC. If one axis channel develops a fault — whether an IPM alarm on the L axis or an overcurrent on the N axis — the entire module goes into fault state and all three axes stop. This is fundamentally different from a cabinet built with three separate single-axis modules, where one failing drive leaves the other two operational. It's one of the practical trade-offs of the three-axis compact form factor: smaller cabinet footprint, but a single-unit failure takes down all three axes simultaneously. For machines where spindle uptime is critical, having a tested spare H304 on the shelf is worth considering.

Q2: What do the alarm codes on the H304's LED display mean, and how do I read them?

The H304 has a single 7-segment LED display that cycles through axis-specific alarm codes. Single-digit codes apply to the module overall — for example, code 1 indicates the internal cooling fan has stopped, code 5 is a DC link low-voltage alarm, and code F means the external cooling fan has stopped. When an axis-specific fault occurs, the display shows a letter or number identifying both the fault type and the axis: codes 8, 9, and A indicate overcurrent on the L, M, and N axes respectively, while codes beginning with the same characters but in a different sequence indicate IPM (Intelligent Power Module) faults on the same axes. The combination codes (b, C, d, E) cover multi-axis simultaneous faults. Checking which specific alarm code appears before removing the module is important — an FSSB communication error (code L or U) points to the fiber optic cable or the CNC card, not the drive hardware itself.

Q3: My machine shows an N-axis IPM alarm on this module. Does that mean the module has failed, or could the motor be the cause?

An IPM alarm on the N axis (the high-current channel) can originate from either the drive hardware or the motor and its cabling. The IPM in the drive detects excessive current draw and shuts down to protect itself — but the reason for that excess current could be a shorted motor winding, a damaged motor power cable with insulation breakdown, or a genuine drive hardware failure. Before condemning the module, it's worth measuring the insulation resistance between each motor phase and the motor frame with a 500V DC megohmmeter — a reading below 1 MΩ suggests the motor or cable is the source of the fault. If the motor and cable check out clean, and the alarm returns immediately after a reset even without motion commanded, that points more directly to the drive module itself.

Q4: Is the A06B-6117-H304 compatible with both FANUC 0i and 30i/31i controllers?

Yes, the 6117 Alpha i series is compatible with both control generations. On a FANUC 0i-C or 0i-D system, the H304 connects via FSSB to the CNC's servo card and operates with that controller's parameter set. On a 30i, 31i, or 32i system, the same module operates under a different — and more capable — parameter environment that supports the full HRV3 current control algorithms the hardware is designed for. The physical hardware is the same; the control performance depends on what the CNC is configured to use. If you're fitting a replacement H304 from stock into a machine, the servo parameters already stored in the CNC apply to the replacement module without change, provided the replacement is the same part number and the motor types and encoder configurations haven't changed.

Q5: The module has two cooling fans mentioned — what maintenance do they need, and how does a fan failure affect the machine?

The H304 has an internal fan (inside the module enclosure) and an external fan mounted on the heatsink fins. The internal fan circulates air across the power devices inside the module; the external fan assists heat dissipation from the heatsink. Fan failures trigger specific alarms: code 1 for internal fan stop, code F for external fan stop. Both fans are replaceable without replacing the entire module — fan life is typically rated in the range of 10,000–30,000 operating hours depending on ambient temperature, so in a machine running two or three shifts daily, fan replacement on a 5–7 year cycle is reasonable preventive maintenance. A fan failure doesn't cause immediate catastrophic damage, but the thermal protection system will fault the module out if internal temperatures rise above the trip threshold — which can happen quickly under load in a warm cabinet. Keeping the cabinet interior clean and unobstructed, and monitoring the fan alarm codes during routine checks, extends module life significantly.

Request a quote or confirm availability: Contact Ms. Amy — sales01@sande-elec.com | Skype: sandesales01 | Tel: +86 18620505228