AC servo motor
Kollmorgen AKM AC servo motor
Kollmorgen's long-running brushless AC servo motor range, spanning eight frame sizes from tiny 40 mm units to 260 mm high-torque motors, with a wide menu of feedback devices and washdown/food-grade options.
Need this part, a replacement or a better-fit option? Our engineers help with selection, procurement, sourcing, competitive pricing and lead times.
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Need Kollmorgen parts, a replacement or another suitable option? Send your part number or describe the application. We’ll review the requirement and help with product selection, sourcing, pricing and lead times.
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Key specifications
| Ingress protection | IP54 standard; IP65 with shaft seal; IP67 washdown / food-grade variants |
|---|---|
| Peak torque (max) | 434 Nm |
| Continuous torque (max) | 180 Nm |
| Speed (max) | 8,000 rpm |
| Power (max) | 19,800 W |
| Frame sizes | 40, 260 mm |
| Supply | AKM1x up to 240 Vac (320 Vdc); AKM2x and larger up to 480 Vac (640 Vdc) |
| Feedback | resolver, commutating encoder, BiSS optical sine encoder, SFD / SFD3 / SFD-M, HIPERFACE, HIPERFACE DSL, EnDat 2.2 (optical and inductive) |
| Frame count | 8 |
Summarised in our own words from Regal Rexnord Corporation's published data; series maxima, individual models vary. Last checked 2026-10-29. Source 1
Notes on this data
Selection guide summary says 0.16-180 Nm continuous; spec tables show 0.18 Nm (AKM11B) to 180 Nm (AKM84T). Peak 434 Nm and 19.8 kW are AKM84T at 240 Vac. 'Speeds up to 8000 rpm' is the guide's headline; AKM5-7 rated to 6000 rpm and AKM8 to 3000 rpm.
Specify Motion is not affiliated with Regal Rexnord Corporation. Kollmorgen and AKM are used only to identify the product. Comparisons use published figures; always confirm against the current datasheet.
Engineer support
Speak to our engineers about your project
Our experienced engineers are on hand, ready to help with your project. Whether you need the Kollmorgen AKM itself, help sourcing it, or a modified or custom design built around your load, speed and space, tell us what the machine has to do and we'll come back with the right option.
- Help sourcing AKM and spares for installed machines
- Modified and custom designs when a catalogue part doesn't fit
- Complete axis: motor, drive, gearing and feedback matched together
Kollmorgen AKM model codes
Published model codes in the AKM range, with key figures from the manufacturer's data. Search this page for your part number, or send it to us for availability or an equivalent.
Typical applications
What an AC servo motor is
An AC servo motor is a permanent-magnet synchronous motor designed for closed-loop control of position, speed and torque. A wound stator is driven by a servo drive with sinusoidal three-phase current, while magnets on the rotor follow the rotating field. A high-resolution encoder or resolver on the shaft feeds position back to the drive, which adjusts current many thousands of times a second. The result is precise, dynamic motion with high peak torque, typically about three times the continuous rating for short periods.
When engineers choose an AC servo motor
Choose an AC servo for machine axes needing fast, accurate motion under varying loads, such as packaging, robotics, machine tools and printing. Compared with steppers, servos keep torque at high speed and cannot silently lose position. The trade-offs are cost and set-up: a servo needs a matched drive, feedback and tuning. For simple, low-speed indexing with a steady load, a stepper may be cheaper. For very low speeds and high torque, a gearbox or direct-drive motor may be needed.
How to specify the Kollmorgen AKM
Send these with your enquiry and an engineer can confirm the right AKM variant or an equivalent:
- Continuous and peak torque (Nm)
- Rated and maximum speed (rpm)
- Load inertia and inertia ratio
- Supply voltage: 230 V single-phase or 400 V three-phase
- Feedback: incremental or absolute encoder, resolution (bits)
- Holding brake, IP code and shaft options
- Flange size and mounting (mm)
Common mistakes to avoid
- Sizing on peak torque without checking RMS torque over the cycle
- Ignoring load-to-motor inertia ratio, which makes tuning hard
- Forgetting the brake is for holding, not dynamic stopping
- Using a motor and drive pair that the supplier has not matched
Kollmorgen AKM: frequently asked questions
Can you help replace Kollmorgen AKM or source the original?
Send the full model code, quantity and required date. Our engineers can check original-part availability and assess suitable alternatives, including Motion Control Products options where appropriate. We confirm compatibility and any changes needed before recommending a replacement.
What is the Kollmorgen AKM?
Kollmorgen's long-running brushless AC servo motor range, spanning eight frame sizes from tiny 40 mm units to 260 mm high-torque motors, with a wide menu of feedback devices and washdown/food-grade options. Published series figures include peak torque 434 Nm, continuous torque 180 Nm, speed 8,000 rpm, power 19,800 W. It is made by Regal Rexnord Corporation; Specify Motion can help source it or propose an equivalent.
What model codes are in the Kollmorgen AKM range?
The AKM range includes AKM11B, AKM11C, AKM11E, AKM12C, AKM12E, AKM13C, AKM13D, AKM21C and 103 more. The table on this page lists each published model code with its key figures. Send us the code you use, or the one you need to replace, and our engineers will confirm availability, lead time or the closest equivalent.
Who makes the Kollmorgen AKM?
The Kollmorgen AKM is made by Kollmorgen (Regal Rexnord Corporation) and is listed here for engineers comparing options. Specify Motion is not affiliated with Regal Rexnord Corporation; brand names are used only to identify the product.
What is the peak torque of the Kollmorgen AKM?
The published series maximum peak torque is 434 Nm. Individual models and sizes in the AKM range vary, so check the exact variant against your duty cycle, mounting and environment, or ask our engineers to confirm the right size for you.
Is there an alternative to the Kollmorgen AKM?
We can assess suitable replacement options. Our engineers can review the original model and propose options for your load, speed and environment. An engineer confirms the fit against your application before recommending anything.
What is the inertia ratio in servo sizing?
The inertia ratio compares the load inertia reflected to the motor shaft with the motor's rotor inertia. High ratios make the axis harder to tune and slower to settle. Many engineers aim for below about 10:1, and lower for highly dynamic axes, using a gearbox to reduce reflected inertia where needed.
Do AC servo motors need an absolute encoder?
Not always. Incremental encoders need a homing routine after power-up, which is acceptable on many machines. Absolute encoders know their position at power-on, avoiding homing, which saves time and suits robots and multi-axis machines. Multi-turn absolute encoders track turns even when power is off.
Further reading: How to select a servo motor · Servo vs stepper · Servo and stepper motors
Other ac servo motor series
Engineer support
Our engineers are ready to help with your project
Tell us about your project and how you use the Kollmorgen AKM: the load, speed, duty and environment. An experienced engineer will review it and reply, normally within one working day.
- Reviewed by an engineer, not an autoresponder
- Like-for-like and better-fit alternatives
- Standard, modified and custom options
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