A06B-6120-H045 Fanuc Power Supply Module A06B6120H045 AO6B-6I2O-HO45

Fanuc A06B-6120-H045 | Alpha i HV Power Supply PSM-45HVi — 150mm Housing, 1200V Transistors, 50kW, 400–480V Input, Wiring PCB A16B-2203-0637, AL-A / AL-2 Fan Diagnosis

Overview

The Fanuc A06B-6120-H045 is the 50kW module in Fanuc's first-generation alpha i HV (high-voltage) power supply family — the A06B-6120 series that takes 400–480V three-phase directly from the facility supply and converts it to the elevated 565–679V DC bus that HV-rated alpha i servo and spindle amplifiers depend on.

Its 150mm wide housing is the physical identifier that sets it apart in the electrical cabinet: narrower than the largest PSM classes in the 200V series, but substantially broader than the 90mm or 60mm modules, reflecting the heat dissipation and component space requirements of a 50kW, 92A design working with 1200V-rated transistors.

The 1200V transistor rating is not arbitrary.

The DC bus this module produces swings between 565V at the low end and 679V during normal operation, with transient peaks above this during active regeneration events. Transistors switching this bus must have blocking voltage ratings comfortably above the peak bus voltage — the 1200V rating provides the necessary derating margin.

This is one of the clearest engineering differences between the 200V aiPS family (A06B-6110) and the HV family (A06B-6120): the HV transistors are a different specification entirely, chosen for the elevated bus voltage rather than merely scaled up from the 200V design.

The wiring PCB inside the A06B-6120-H045 carries Fanuc part number A16B-2203-0637.

This board handles the interface functions between the module's internal circuits and the power connections to the external supply and DC bus. Like other alpha i PSM board assemblies, it is not available as a standalone spare part through standard channels — module exchange or specialist board repair are the service paths when a board-level fault is diagnosed.

Key Specifications

150mm Housing — Cabinet Planning and Mechanical Fit

The 150mm width places the PSM-45HVi in the same housing class as several mid-range modules in the 200V alpha i family. In an HV drive rack, the PSM-45HVi is flanked by the alpha i HV SVM and SPM modules on its DC bus side, and the AC reactor and supply connections on the other.

The mechanical layout follows the same bus bar arrangement as the 200V series — top and bottom bus bar connections for the DC link, side connectors for control power and alarm signals.

A machine originally designed for the PSM-45HVi will have the cabinet slot dimensioned for 150mm; fitting a different width module would require physical modification of the mounting arrangement.

For machine builders sourcing a PSM-45HVi for a new build, the 150mm standard format means the module integrates into drive racks using the same mounting hardware and bus bar assemblies specified by Fanuc for the HV family.

For maintenance engineers sourcing a replacement, the 150mm format is a useful verification parameter — confirm that the replacement unit is the 150mm variant before ordering, as the A06B-6120 family spans several power classes with different housing widths.

The 565–679V DC Bus — Why These Voltages

The 400V AC three-phase supply has a peak line-to-line voltage of approximately 566V (400 × √2). The three-phase diode bridge in the PSM-45HVi's input rectifier charges the DC bus capacitors to this peak value at no load — hence the 565V lower limit of the regulated output range.

Under the voltage regulation of the active front end, the bus is held within 565–679V during normal operation. The upper limit represents the maximum permitted bus voltage before the overvoltage protection circuit (AL-7) intervenes.

During rapid spindle deceleration — a 22kW spindle motor going from 6000 rpm to zero in under two seconds, for example — the motor acts as a generator, pushing current back toward the bus. The active front end inverts this energy back into the 400V supply rather than allowing the bus voltage to climb to AL-7.

The effectiveness of this active regeneration is why the PSM-45HVi is specified for large machines with high-inertia spindles; without it, the regenerated energy from a heavy spindle deceleration would require a very large discharge resistor, and the cabinet heat load during a shift of repeated spindle accelerations and decelerations would be severe.

Fan Alarms: AL-2 and AL-A in the HV System Context

The PSM-45HVi uses the same dual-fan architecture as the 200V alpha i PSM family, and the alarm separation between AL-2 (internal fan) and AL-A (external heatsink fan) carries even more urgency at 50kW output than at lower power levels.

At 50kW, the heat generated in the 1200V transistor modules under rated load is substantial.

The external heatsink fan (A90L-0001-0509) is the primary mechanism for removing this heat — it forces ambient air through the finned heatsink block where the transistors mount. If this fan stops (AL-A), the heatsink temperature climbs rapidly. How rapidly depends on the load: at 50kW output in a production cut, the temperature rise rate without the fan is significantly faster than at partial load.

The margin between ambient and the AL-3 (heatsink over-temperature) protection threshold is consumed in minutes rather than hours. AL-A on a PSM-45HVi in production is therefore a stop-and-investigate alarm, not a log-and-continue one.

The internal fan (A90L-0001-0441#39) serves a different but equally important role: it manages the thermal environment of the control PCB inside the module housing. PCB temperature influences the long-term reliability of electrolytic capacitors and other temperature-sensitive components on the control board.

AL-2 (internal fan stopped) warrants immediate fan replacement — continued operation with the internal fan failed accelerates the ageing of control board components at a rate that shortens module service life measurably.

Both fans are separately stocked spare parts and can be replaced without exchanging the complete module.

First-Generation A06B-6120 in the Field Today

The A06B-6120 first-generation HV aiPS series was produced during the same era as the A06B-6110 200V family — roughly 2004 to the late 2000s, before the A06B-6150 second-generation HV series superseded it.

Machines built in that production window are now approaching or exceeding fifteen years of service, which means the PSM-45HVi units currently in the field are entering the age range where proactive thermal component inspection and fan replacement makes strong economic sense.

An unplanned production stop on a large machining centre — the typical machine for PSM-45HVi — carries a substantially higher hourly downtime cost than a scheduled maintenance stop.

FAQ

Q1: Can the PSM-45HVi be used on a 480V North American supply in addition to 400V European supply?

Yes. The 400–480V input range accommodates both the 400V supplies standard in Europe and the 480V (line-to-line) three-phase supplies common in North American industrial facilities. Both 50Hz and 60Hz are supported.

The module's active front end regulates the DC bus output within 565–679V across this entire input range, maintaining consistent performance regardless of whether the facility supply is 400V/50Hz or 480V/60Hz.

Q2: When the PSM-45HVi shows AL-3 (heatsink over-temperature), is this always a cooling failure, or can it indicate a failing transistor?

AL-3 is triggered by a thermal sensor on the heatsink exceeding its threshold. The most common cause is a cooling failure — AL-A (external fan stopped) that was missed or deferred, or a blocked heatsink with dust and swarf accumulation preventing airflow.

A failing transistor that is drawing higher-than-normal quiescent current can also generate excess heat and eventually push the heatsink temperature to the AL-3 threshold, even with the fan running. 

If AL-3 occurs with both fans confirmed operational and the heatsink fins clean, the transistor modules warrant inspection. If AL-A preceded AL-3, restore cooling first; the AL-3 will clear once the heatsink cools, and the transistors may be undamaged if the overheat event was brief.

Q3: How does the PSM-45HVi's first-generation A06B-6120 series relate to the second-generation HV aiPS modules? Is there a replacement designation?

The second-generation alpha i HV PSM family carries the A06B-6150 series designation. The A06B-6150-H045 is the second-generation equivalent of the A06B-6120-H045, providing the same 50kW output at the same 400–480V input and the same 565–679V DC bus output.

The two are compatible with the same downstream alpha i HV amplifier modules (A06B-6127 SVM, A06B-6121 SPM). Fitting an A06B-6150-H045 as a replacement for a failed A06B-6120-H045 requires no parameter changes or rewiring adjustments.

Q4: The A06B-6120-H045 wiring PCB is A16B-2203-0637. Is this the same board used in other A06B-6120 series modules?

The A16B-2203-0637 appears in the A06B-6120-H045 specifically. Other A06B-6120 series modules (different power classes) may use different board part numbers.

When sourcing a board-level repair for the H045, the A16B-2203-0637 designation must be matched precisely — substituting a board from a different A06B-6120 variant is not appropriate without verification that the board specifications match. 

For most field situations, whole-unit exchange is more practical than board-level sourcing.

Q5: What AL code appears when the PSM-45HVi input loses one phase, and how should it be investigated?

AL-E indicates the module has detected an open-phase condition — one of the three AC input phases is missing or severely reduced. Investigation steps: check all three input fuses individually (a single-phase open fuse is a common cause and is not always visible by visual inspection alone — use a multimeter to confirm continuity), confirm the circuit breaker feeding the module has not opened on one pole, and measure the three phase voltages at the PSM-45HVi input terminals under load to rule out a supply cable fault. AL-E does not indicate an internal PSM fault; it is a supply quality event.