AC servo motor
B&R Industrial Automation 8KS synchronous motors
Large synchronous servo motors up to 140 kW with stall torque up to 555 Nm air-cooled (575 Nm water-cooled 8KSJ9) and speeds to 3,000 rpm, with fan or water cooling.
Need this part, a replacement or a complete package? Our experienced UK engineering team helps you select, source and obtain the right products, with pricing, delivery coordination and after-sales support.
Pricing and availability
Get pricing, sourcing and replacement support
Need B&R Industrial Automation parts, a replacement or a suitable alternative? Send us a part number, or tell us what the machine needs to do. Our UK engineers will come back with the right product, pricing, lead time and delivery, whether that is the original part, a checked alternative or a complete axis.
- Original parts or a checked alternative
- Pricing, lead time and delivery in one reply
- Components, complete axes and ongoing support
No obligation. Add what you know and an engineer will help with the rest. Prefer to configure it? Build a specification.
Spec builder
Specify what you need instead of 8KS synchronous motors
Select every part you need and answer the questions an applications engineer would ask. Our engineers use your specification to come back with the right products, pricing and lead times. You see your summary before we ask for any details.
Already know the part number? Send it to us directly.
- 1Products
- 2Performance
- 3Environment
- 4Volumes
- 5Your spec
What are you specifying?
Select everything you need. A motor, drive and gearbox can be specified together as one axis.
Key specifications
| Standstill torque (max) | 575 Nm |
|---|---|
| Speed (max) | 3,000 rpm |
| Power (max) | 140,000 W |
| Frame sizes | 240 x 240, 320 x 320 |
| Cooling | radial fan, axial fan or water |
Summarised in our own words from ABB's published data; series maxima, individual models vary. Last checked 2026-10-30. Source 1
Notes on this data
Page text quotes 'up to 555 Nm'; its table lists 575 Nm stall torque for the water-cooled 8KSJ9.
Specify Motion is not affiliated with ABB. B&R Industrial Automation and 8KS synchronous motors 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 B&R Industrial Automation 8KS synchronous motors 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 8KS synchronous motors 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
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 B&R Industrial Automation 8KS synchronous motors
Send these with your enquiry and an engineer can confirm the right 8KS synchronous motors 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
B&R Industrial Automation 8KS synchronous motors: frequently asked questions
Can you help replace B&R Industrial Automation 8KS synchronous motors 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 supply-network options where appropriate. We confirm compatibility and any changes needed before recommending a replacement.
What is the B&R Industrial Automation 8KS synchronous motors?
Large synchronous servo motors up to 140 kW with stall torque up to 555 Nm air-cooled (575 Nm water-cooled 8KSJ9) and speeds to 3,000 rpm, with fan or water cooling. Published series figures include standstill torque 575 Nm, speed 3,000 rpm, power 140,000 W. It is made by ABB; Specify Motion can help source it or propose an equivalent.
Who makes the B&R Industrial Automation 8KS synchronous motors?
The B&R Industrial Automation 8KS synchronous motors is made by B&R Industrial Automation (ABB) and is listed here for engineers comparing options. Specify Motion is not affiliated with ABB; brand names are used only to identify the product.
What is the standstill torque of the B&R Industrial Automation 8KS synchronous motors?
The published series maximum standstill torque is 575 Nm. Individual models and sizes in the 8KS synchronous motors 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 B&R Industrial Automation 8KS synchronous motors?
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 B&R Industrial Automation 8KS synchronous motors: 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
Prefer to configure it? Use the spec builder.
How it works
From enquiry to delivery
Send a part number or describe the application. Our engineers take it from there: the right product, a clear quotation, and delivery and support arranged.
- 01Tell us what you needSend a part number, or configure the application, quantities and timing.
- 02An engineer reviews itWe check the specification and find the original part, a checked equivalent or a complete axis.
- 03Receive your quotationProducts, pricing, lead time and compatibility notes in one reply.
- 04Order and deliveryWhen you are happy, the order is placed and delivery and after-sales support are arranged.