Beckhoff / AX servo drives and AM motors

An AX5000 DC link holds up to 875 V DC after the power is off. Beckhoff specifies a five minute discharge and requires the terminals measured below 50 V before anyone touches them.

AX is the Beckhoff servo drive range and AM the motor range, both EtherCAT native and common on New Zealand machine building.

Safety first: the DC link stays live

Putting this at the top because it is the most serious thing on the page.

Discharge times vary by model. The figures above are for the smaller frames; larger drives take longer.

Isolating the supply does not make the drive safe. Wait, then measure.

The second digit is the axis count

The AX5000 numbering is clean once you see it.

So AX5103 is a single-axis 3 A drive and AX5203 is a dual-axis 3 A drive.

The range runs 1.5 A to 170 A, up to 118 kW output.

Full order codes carry a dash suffix, in the form AX5103-0000-020x. Send the whole thing.

Why the dual-axis version is cheaper

Worth understanding because it is a genuine saving and it has a constraint.

Beckhoff describes the two-channel drive as two fully self-contained servo drives sharing expensive components: the power supply unit, ballast circuit, mains filters and DC link capacitors.

And the power can be adjusted variably between the two axes, so an unequal pair can share one drive sensibly.

The constraint follows from the sharing: a fault in the shared power section takes out both axes. On a machine where the two axes must fail independently, that is a design consideration rather than a cost one.

And you cannot replace one half. A dual-axis drive is one part.

One Cable Technology

The thing that changed Beckhoff servo installations, introduced in 2011.

OCT carries motor current and encoder feedback on a single cable. There is no separate feedback cable.

OCT works with AM8000 series motors. Both the AX5000 and AX8000 support it.

If an installation is OCT, the cable is a specific part and a conventional motor cable will not do. Tell us which arrangement you have.

The AM8000 motor carries its own tuning

Genuinely useful, and it changes what commissioning a replacement motor involves.

AM8000 motors have a digital identification plate holding:

Beckhoff states these are loaded immediately after communication starts between the controller and the motor.

So fitting a replacement AM8000 is close to plug and play. The drive reads the motor and configures itself.

The cogging suppression figures are the interesting part: they were measured on that individual motor at the factory, not taken from a model average.

Third-party motors are a different job

The contrast is stark.

For a non-Beckhoff motor, the motor parameters must be configured through TwinCAT Drive Manager and a commutation offset calibration must be performed.

So a third-party motor is a commissioning exercise, not a swap. Worth knowing before someone fits a cheaper motor to save money on a replacement.

The AM motor variants

A clean table, and the differences are physical rather than electrical.

Two of these matter in New Zealand

AM8800 stainless is the washdown motor. In meat and dairy, a standard motor in a caustic wash corrodes and the failure looks like a motor fault rather than a specification error.

AM8500 increased inertia is not a cosmetic difference. A higher-inertia motor matches a high-inertia load better and runs more stably. Substituting a standard AM8000 gives you a motor that will run and may need retuning to stay stable.

Check the series digit before ordering.

The feedback interface, and the option card

An ordering trap on the AX5000.

The fully digital feedback systems need an option card in the drive. A standard AX5000 will not read them.

So if the existing drive has an option card fitted, a plain replacement of the same current rating will not commission. Check the drive, not just the motor.

On the AX8000, Beckhoff offers an optional multi-feedback interface covering EnDat 2.2, BiSS-C, TTL and SinCos 1 Vss for third-party motors.

The AX5000 takes almost any motor

Worth knowing when a machine has an unusual actuator.

Beckhoff states that synchronous, linear, torque, asynchronous and voice coil motors can be connected without additional measures.

That flexibility is why AX5000 turns up on specialist machines where a conventional servo drive would not suit. If a machine has a linear motor or a voice coil actuator, the drive is probably an AX5000.

AX-Bridge

The quick connection system that links drives into a multi-axis group.

Beckhoff notes it significantly reduces wiring work and rules out connection errors. On the AX8000 the AX-Bridge includes spring balancer technology for tool-free mounting.

The shared DC link is the functional point. One axis decelerating feeds energy to another accelerating, rather than dumping it in a brake resistor.

AX-Bridge components are separate parts. If you are adding an axis to an existing group, the bridge modules are on the list.

AX8000 multi-axis

Mixing axis module ratings is the design advantage. A machine with one large axis and three small ones does not need four identical drives.

And the power supply module is a separate part from the axis modules. When quoting a replacement, establish which failed.

TwinSAFE in the drive

The AX8000 supports up to 17 drive-integrated safety functions and meets EN ISO 13849-1:2015.

TwinSAFE Logic runs in the axis module itself, so safety functions are programmed directly in the drive rather than in a separate controller. Beckhoff cites shorter response times as the benefit.

So an AX8000 may be carrying part of the machine's safety function. A replacement needs the same TwinSAFE capability and the safety project reloaded.

As with every safety part on this site, whether a substitution is valid belongs with whoever holds the machine's assessment.

AMP8000

A distributed arrangement worth knowing exists: AMP8000 combines an AM8000 servomotor with an integrated servo drive.

The drive is in the motor, so there is no cabinet drive at all. That removes panel space and cabinet heat.

If a machine has motors with no corresponding drives in the panel, that is why.

A UL note

Relevant on machinery built for or exported to North America.

Beckhoff specifies that a UL-listed AX5000 shall be connected only to a grounded wye source where the maximum voltage does not exceed 277 V to ground, and that the nameplate carries a CUS symbol where UL listing applies.

If you are checking whether a drive is UL listed, the nameplate is the place to look.

What to send us

The full drive order code including the dash suffix.

Single or dual axis. The second digit tells you.

Whether an option card is fitted, for EnDat 2.2 or BiSS-C feedback.

The motor type and series. AM8000, AM8300, AM8500, AM8700 or AM8800.

Whether the installation is OCT.

Whether the drive carries TwinSAFE functions.

For an AX8000, whether the power supply module or an axis module failed.

What we can supply

Current production. AX5000 single and dual axis across the current range, AX8000 power supply and axis modules, AM8000 series motors in all variants, AX-Bridge components, brake resistor modules, OCT cables and option cards. Quoted with a delivered lead time.

Discontinued. Earlier AX and AM variants. Surplus and tested used.

Cables and bridge components separately. Often the missing item on a multi-axis extension.

We buy Beckhoff servo

AX drives and AM motors hold real value, and matched drive and motor pairs are worth more together. Keep OCT cables with them, since they are specific parts.

If you are decommissioning a machine, see Sell To Us.

Related

Beckhoff overview, EtherCAT Terminals and CX embedded PCs.

For servo from other brands see Allen-Bradley Kinetix, Omron G5 and 1S, Schneider Lexium and ABB MicroFlex.

Send us your order codes

The second digit is the axis count and the last two are the current. And wait five minutes and measure the DC link before working on one. Quotes in NZD including GST.

Request a quote

Industech is an independent supplier of new, surplus and used industrial automation equipment. We are not an authorised distributor of, approved by, sanctioned by, or affiliated with Beckhoff Automation. Beckhoff, TwinCAT, TwinSAFE, EtherCAT and One Cable Technology are trademarks of Beckhoff Automation. All trademarks, brand names and part numbers are the property of their respective owners and are used here for identification purposes only. Information on this page is for identification and does not constitute electrical or safety design advice.