Power Supply A06B-6091-H118 A06B6091H118 AO6B-6O91-H118

FANUC A06B-6091-H118 | Alpha Power Supply Module PSM-18HV — 400 VAC High-Voltage Input, Regenerative DC Bus, Capacitor Module Required, Alpha Series HV, Japan Origin

Part Number: A06B-6091-H118

Manufacturer: FANUC Corporation (Japan)

Product Category: Power Supply Module — Alpha Series HV (High Voltage)

Model: PSM-18HV

Overview

The FANUC A06B-6091-H118 is the PSM-18HV — the 18 kW power supply module in FANUC's Alpha series high-voltage (HV) drive family.

The A06B-6091 series is the 400-volt input class of the original Alpha series drive system, distinguished from the 200-volt-class modules by the HV designation and by its requirement for a paired capacitor module (PSMC-HV).

This module was developed for industrial markets operating on 400-volt AC supplies, covering much of Europe, parts of Asia, and other regions where the standard industrial three-phase supply voltage is in the 380–480 V range.

The PSM-18HV functions as the central DC bus power supply for a FANUC Alpha series drive system rack in a 400-volt installation.

It converts the three-phase 400-volt AC input to a regulated high-voltage DC bus that feeds the servo amplifier modules (SVM) and spindle amplifier modules (SPM) connected in the same drive rack.

Like all PSM modules in the Alpha series, the PSM-18HV is a regenerative type — deceleration energy from servo axes and the spindle is returned to the AC supply rather than burned off as heat.

This module belongs to the first generation of FANUC's Alpha drive architecture — the original Alpha series that preceded the Alpha i generation.

These modules are characterised by their yellow housing (compared to the Alpha i series grey/silver housings) and their reliance on external capacitor modules. 

A significant number of FANUC-controlled machine tools worldwide still run on Alpha series drives, making the PSM-18HV an active maintenance item for this installed base.

Key Specifications

HV Series Architecture — Why a Capacitor Module Is Required

A key structural difference between the Alpha series HV modules (A06B-6091 series) and other PSM variants is the mandatory external capacitor module. Each PSM-HV requires a paired PSMC-HV capacitor module. For the PSM-18HV, the required capacitor module is the PSMC-18HV (ordering number A06B-6083-H218).

The DC bus capacitor bank serves several functions in the drive system:

Energy storage buffer. Short-duration power demand peaks from motor acceleration draw on the capacitor bank, allowing the incoming AC rectifier circuit to operate more smoothly and reducing peak current drawn from the mains.

Regeneration absorption. When servo axes decelerate and inject energy back onto the DC bus faster than the regenerative front end can return it to the AC supply, the capacitor bank absorbs the excess transiently, preventing DC bus overvoltage.

Ride-through. The capacitor bank provides a brief energy reservoir that allows the drive system to continue operating through very short input power interruptions.

In the Alpha i generation (A06B-6110 series and others), the capacitor bank is integrated within the power supply module housing — this is one of the integration improvements that distinguish the Alpha i from the original Alpha.

In the original Alpha HV series, the capacitor module is always a separate unit that must be physically installed alongside the PSM-HV in the drive cabinet and connected via dedicated cables.

Alpha HV Drive System — System Configuration

A complete Alpha HV drive system for a 400-volt installation consists of:

PSM-HV (this module): Rectifies 400V AC to DC bus. Manages regeneration back to the AC supply.

PSMC-HV (mandatory companion): External capacitor module. Must be matched to the PSM-HV rating (PSMC-18HV for the PSM-18HV).

SVM-HV servo amplifier modules: One per servo axis (or dual-axis in some configurations). Connected to the common DC bus from the PSM-HV.

SPM-HV spindle amplifier module: If a spindle drive is part of the system. Also connected to the DC bus.

All modules mount in the drive cabinet with shared DC bus connections.

The PSM-HV is the only module connected to the main AC supply — all other modules receive power exclusively through the DC bus.

Service and Maintenance Considerations

The Alpha series HV modules are a mature product line. FANUC has produced Alpha i replacements for most of these functions, but large numbers of original Alpha series HV systems remain in service. Key maintenance considerations for the PSM-18HV:

Cooling. Alpha series HV modules are cooled by the cabinet cooling system and the module's heat sink. Confirm adequate air circulation around the module. Blocked cooling airflow is a leading cause of premature thermal failure in these modules.

Capacitor aging. The PSMC-18HV capacitor module contains electrolytic capacitors with finite service life.

In long-running installations (10+ years), the capacitors age and their capacitance decreases. 

Reduced capacitance manifests as increased DC bus voltage ripple and reduced transient energy absorption. Preventive replacement of aged capacitor modules is recommended for machines approaching this service interval.

Fuse inspection. The PSM-HV contains internal fuses.

If the module has experienced an overcurrent event, inspect the fuse condition as part of the fault investigation.

FAQ

Q1: The PSM-18HV shows an alarm. The PSMC-18HV capacitor module is installed correctly. What should be checked first?

Confirm the three-phase 400V input is present and balanced at the PSM-18HV terminals.

A lost phase or significant voltage imbalance triggers alarms that appear as module faults rather than power faults. 

Then check all DC bus connections between the PSM-18HV, the PSMC-18HV, and the connected SVM/SPM amplifier modules — a loose or corroded bus bar connection causes bus voltage abnormalities. 

Finally, inspect the PSM-18HV's internal fuses if an overcurrent event preceded the alarm.

Q2: Can the PSM-18HV be used without the PSMC-18HV capacitor module?

No. The PSM-HV series requires its paired capacitor module to function. Operating without the PSMC-18HV will result in DC bus instability, overvoltage faults during deceleration, and potential damage to the servo and spindle amplifier modules on the bus.

Always install and connect the correct PSMC-HV before powering the system.

Q3: The machine was previously running on a 380V supply. It is being moved to a 415V supply. Is the PSM-18HV still compatible?

The A06B-6091 HV series is rated for the 400V class AC input, which covers the common international range of 380–480V three-phase.

A 415V supply falls within this range and does not require modification of the module. 

Confirm the new supply voltage is within the module's specified input voltage tolerance before commissioning.

Q4: Is it possible to replace the PSM-18HV with an Alpha i generation equivalent?

Upgrading from an original Alpha series HV drive to an Alpha i HV drive is possible but is not a simple module swap — it requires replacing the SVM and SPM amplifier modules as well, since Alpha and Alpha i amplifier modules are not directly interchangeable on a shared DC bus.

 A full system upgrade from Alpha HV to Alpha i HV is a planned project involving new amplifiers, new PSM, new wiring, and servo parameter reinitialisation.

Like-for-like replacement with another PSM-18HV (A06B-6091-H118) is the standard maintenance path when the existing system is otherwise functional.

Q5: How should the PSM-18HV be stored when removed from service?

Store in a clean, dry environment at room temperature, away from direct sunlight and corrosive atmospheres.

Place the module in an antistatic bag or wrap with antistatic material. 

If the paired PSMC-18HV is also being stored, discharge the capacitor module fully before storage and do not reconnect it to AC power after extended storage without first checking the capacitor condition. 

Allow a cold module stored below ambient temperature to reach room temperature before applying power after reinstallation.