Harmonic Drive REL EtherCAT AC Servo Drives Review: Specs, Price and Applications
Updated: 4 days ago
REL is an AC-line servo-drive family with CANopen over EtherCAT command communication and configuration-specific actuator feedback support. Harmonic Drive documents REL combinations with identified FHA, SHA, RSF and RKF actuators rather than offering an unrestricted promise of compatibility with every motor bearing those family names. Select the drive, winding, encoder and cable set as one approved axis.
Quick Verdict
Consider REL when an AC-powered EtherCAT axis and a documented actuator-drive combination match the machine architecture. Separate the drive’s output-current rating from actuator demand and line-supply current. EtherCAT connectivity alone does not establish feedback compatibility, thermal capacity, brake sequencing or a complete safety function.
Harmonic Drive REL EtherCAT AC Servo Drives at a Glance
Specification | Details |
Supply class | Manufacturer general catalog:100–240 VAC for listed REL-230 models |
REL-230-18 current | 6 Apk continuous;18 Apk peak in catalog |
REL-230-36 current | 12 Apk continuous;36 Apk peak in catalog |
REL-230-40 current | 20 Apk continuous;40 Apk peak in catalog |
Network command | CANopen over EtherCAT(CoE); controller and drive configuration required |
Motion functions | Indexer, point-to-point, PVT, camming, gearing, position, velocity and torque |
Other command inputs | ASCII/discrete I/O, stepper commands, ±10 V, PWM and master-encoder functions as documented |
Digital I/O | 15 inputs;6 outputs in product-page specification |
Analog I/O | Two 16-bit inputs and one 12-bit output in product-page specification |
Envelope | 202×139×52 mm; installation clearance and accessories additional |
Feedback scope | Documented incremental and absolute variants; exact drive/actuator combination governs |
Price | Request a quote for drive, matched actuator, feedback, cables and accessories |
Design and Engineering Assessment
The REL-230-18 model suffix should not be read as 18 A continuous output. The catalog lists 6 Apk continuous and 18 Apk peak. REL-230-36 lists 12/36 Apk, while REL-230-40 lists 20/40 Apk. The Apk notation is important: these values should not be silently relabeled as RMS motor-phase current or AC line-input current.
The product page separately tabulates actuator continuous and peak currents for identified supply, ratio, winding and encoder combinations. Those rows describe actuator demand, not a new drive rating. For example, an FHA winding selected for an AC100 V combination should not be substituted into an AC200 V row just because the mechanical actuator size matches.
CoE describes CANopen application-layer communication carried over EtherCAT. It is not the same physical connection as a separate CANopen bus or DeviceNet network. The controller must support the applicable drive interface, configuration and synchronization requirements. A broad supplier portfolio description listing several networks does not put all of them on every REL unit.
Incremental and absolute encoder support is configuration-specific. The manufacturer lists 14-wire incremental,4-wire serial incremental and several absolute feedback arrangements in the wider catalog. The actual motor feedback, drive capability, connector and cable must match; counting wires or sharing an actuator family label is not sufficient.
Actuator, Winding and Drive Selection
Start with the full actuator ordering code and its torque-speed cycle. Confirm motor winding, feedback type, ratio, brake and cable arrangement against the approved drive-combination table. Select the drive current and supply for that configuration, with appropriate thermal and overload evaluation.
A listed peak capability does not establish an indefinitely sustainable torque. Check peak duration and duty, continuous heating, heatsink requirements and enclosure conditions. Include the drive’s actual installation clearance and heat path rather than fitting only the nominal 202×139×52 mm body into a cabinet.
EtherCAT Integration
Establish controller and drive configuration, motion mode, scaling and position reference before enabling a closed-loop production move. Verify limits, direction and feedback validity with controlled low-energy commissioning. EtherCAT communication success by itself does not prove correct motor phasing or stable tuning.
Choose the intended command architecture deliberately. A machine using network motion should not rely on undocumented interactions with simultaneously active analog, pulse or local indexing commands. Keep the configured source of motion commands and the expected enable/stop sequence explicit.
Regeneration, Brakes and Power Design
A decelerating axis can return energy to the drive’s bus. Evaluate the actual inertia, speed and stopping profile against the manufacturer’s regeneration and resistor requirements. The accessory list distinguishes resistor options by drive model; an arbitrary resistor cannot be selected from resistance alone.
An optional actuator holding brake needs the correct power and sequencing. Define when the drive establishes torque, when the brake releases and how a stop is handled. The presence of EtherCAT or a holding brake does not establish a safety-rated stop for the complete machine.
Feedback Wiring andI/O
Use the exact motor and encoder wiring information. Shielding, grounding, connector pinout and cable separation affect reliable operation. A feedback interface can be electrically incompatible even when it reports a familiar encoder resolution.
The listed digital and analog channel counts describe hardware resources, not a finished machine-control design. Confirm signal levels, assigned functions, filtering and diagnostic coverage for the actual application. Do not treat a general-purpose input as an independent safety input without the corresponding documented function.
Acceptance and Maintenance
Validate direction, travel limits, homing or absolute-position recovery and brake behavior before applying the full load. Then run a representative cycle and examine current, temperature, following error and settling. Keep the actuator and drive parameter backup associated with the exact hardware.
For replacement planning, confirm current model support and approved alternatives with the supplier. A published pairing or an older availability statement is not proof of present stock. Compare the complete configured axis, including cables, network setup and commissioning effort, in the purchase decision.
Applications and Selection
AC-powered EtherCAT positioning axes using supported Harmonic Drive motor/actuator combinations
For Harmonic Drive REL EtherCAT AC Servo Drives, define the actual machine duty before selecting an ordering configuration. Include the required operating point, available installation space, environment and control interfaces. The specification table describes the product or family; the surrounding machine determines which of those features matters for the intended job.
Price and Value
Price: Request a quote for the exact configuration. Compare the product, compatible control equipment, required mechanical parts, cabling and commissioning as one installed system. A component price alone does not represent the cost of a working automation axis.
Evaluate an alternative against the same duty and acceptance criteria. Match the continuous operating requirement first, then compare transient capability, feedback, mechanical fit and support. This avoids choosing between superficially similar products whose ratings describe different operating conditions.
Pros and Cons
Advantages
EtherCAT CoE communication supports a networked motion architecture
Published drive and actuator tables enable configuration-specific matching
Multiple feedback and command arrangements are documented for supported combinations
Limitations
Model suffix and Apk ratings must not be mistaken for continuous RMS current
Feedback, winding and cabling require exact compatibility
Power, regeneration, brake and machine safety remain integration responsibilities
Who Should Consider Harmonic Drive REL EtherCAT AC Servo Drives?
machine builders matching a servo amplifier to an approved motor and feedback configuration
Harmonic Drive REL EtherCAT AC Servo Drives FAQ
Does REL-230-18 supply 18 A continuously?
No. The manufacturer catalog lists 6 Apk continuous and 18 Apk peak for that model. Preserve the Apk convention and use the corresponding duty conditions.
What network is documented for REL?
CANopen over EtherCAT(CoE). That is not a separate CANopen or DeviceNet physical bus, and the selected controller must support the applicable drive configuration.
Can every Harmonic Drive actuator be connected?
No blanket compatibility should be assumed. Match the full actuator winding and feedback code to the approved drive, supply, cables and parameter arrangement.
Are actuator current rows the drive’s own ratings?
No. The combination tables describe the actuator’s current requirements under the identified configuration. Compare those requirements with the separate drive ratings using consistent current conventions.
Does absolute feedback eliminate commissioning?
No. Confirm feedback compatibility, reference recovery, direction, scaling, limits and brake sequence. Absolute data does not establish the machine’s safe operating range.
Why is regeneration important?
Deceleration can return energy to the bus. Evaluate the motion profile and use the approved regeneration arrangement, including model-appropriate resistor and thermal requirements where needed.
Are the listed I/O channels safety-rated?
Channel counts alone do not establish a safety rating. Use the exact documented function and design the machine’s required protective measures independently.
What belongs in the quote?
Include the drive code, actuator and winding, feedback, supply, brake, cables, thermal accessories, regeneration needs, controller/network arrangement and required commissioning scope.
Prices are indicative and may change. Confirm the final configuration, commercial terms and delivery schedule before ordering.
