General safety information for servo motors

Important safety information

Unless the specific offer expressly states a different inspection status, used servo motors offered by REHA-Industriekomponenten e.K. are supplied in the condition category “Used, removed from an installation”. In that case, REHA-Industriekomponenten e.K. has not carried out its own electrical inspection or comprehensive operational check.

Before installation and first use, the operator must have appropriately qualified personnel determine, perform and document the required inspections on the basis of the complete motor and system identification, the applicable manufacturer documentation, the specific machine or installation and the requirements at the place of use. Installation, release and commissioning may be decided only after this work has been completed.

Servo motors may carry or generate lethal electrical voltages and can produce high forces, torques, speeds and accelerations within a very short time.

A permanent-magnet servo motor can generate voltage at its terminals when the shaft is turned from outside, even if the servo controller is switched off or disconnected.

Incorrect identification, assignment, connection, mounting, parameterisation, feedback evaluation or brake control can cause electric shock, arc flash, fire, uncontrolled movement, falling loads, serious or fatal injury and substantial property damage.

This page contains general, non-exhaustive supplementary information only. It is not a work instruction and must never be used as the sole or sufficient basis for selection, connection, installation, inspection, release or commissioning.

Before work begins, the applicable documentation for the complete product version, the documentation for the specific machine or installation and the safety requirements at the place of use must be available, reviewed and followed.

If the exact product version cannot be identified, the applicable manufacturer documentation is unavailable, or there is doubt about condition, assignment, compatibility or connection requirements, the component must not be connected, energised, released or commissioned.

Supplementary manufacturer-independent safety information for business operators and qualified personnel

No connection, installation, wiring, inspection, repair, parameterisation or commissioning instructions

Editorial status: 27 August 2026

For sales through reha-components.com, the product description, order confirmation and the International B2B Terms determine the agreed inspection status and contractual terms.

1. Purpose and limits

This page covers recurring hazards associated with rotating industrial servo motors, including synchronous and asynchronous servo motors, motors with resolver or encoder, motors with holding brake, externally cooled motors and servo geared motors.

Special designs such as linear, torque, built-in or explosion-protected motors can involve additional requirements. The exact motor, controller, feedback device, brake, mechanics, cooling and machine safety design are decisive.

No pin assignment, conductor size, supply or brake voltage, encoder supply, motor value, speed limit, torque, cooling time, bearing load, tightening torque or interchangeability statement may be derived from this page.

2. The motor is part of a drive system

A servo motor must be assessed together with the servo controller, motor and feedback cables, encoder, brake, mechanical transmission, load, machine control and safety functions.

Mechanical dimensions or rated power alone do not establish electrical, feedback, brake, thermal or safety compatibility. A motor that fits the flange can still be unsuitable and hazardous in the system.

3. Identify the exact motor and applicable documentation

Record the full manufacturer and order number, winding and voltage version, revision, rated speed and torque class, encoder, brake, connector, cooling, protection, mounting position, shaft and flange version.

Use the exact motor documentation together with the documentation for the assigned servo controller and the current machine drawings, parameters and safety information. Do not transfer connection or performance data from a visually similar motor.

4. Qualified personnel and operator responsibility

Transport, mounting, connection, parameterisation, testing, alignment and commissioning require personnel qualified and authorised for the specific electrical and mechanical work.

The operator must determine the required inspections, lifting method, mechanical safeguards, test conditions and release criteria under the laws, technical rules and manufacturer instructions applicable at the place of use.

5. Generated voltage and electrical isolation

Shaft movement can generate hazardous voltage. Prevent rotation before touching conductors or connectors, isolate all supplies and verify absence of voltage with suitable equipment.

Motor, brake, feedback, temperature-sensor and fan circuits may use separate supplies and potentials. Identify and isolate each circuit; a disconnected power cable does not prove that all motor connections are safe.

6. Unexpected movement and stored mechanical energy

A motor can accelerate immediately when the drive is enabled or when feedback, phasing or parameter data is wrong. Secure the shaft, coupling, load and danger zone before energising the system.

Gravity, springs, counterweights, pressure and coupled mechanics can move the motor when the brake or coupling is released. Provide independent restraint and never rely only on controller torque.

7. Holding brakes and vertical loads

A motor holding brake is normally intended to hold a stationary axis and is not automatically a safety brake or a service brake. Its suitability, wear state, switching voltage, polarity, air gap, release time and control sequence must be verified for the exact application.

Support suspended or vertical loads mechanically before installation or service. Do not work beneath a load held solely by the motor brake or drive control.

8. Encoder, resolver and commutation assignment

Feedback type, supply, signal format, resolution, connector pinning, phase sequence and commutation data must match the motor and controller. Incorrect assignment can cause immediate uncontrolled torque or motion.

Automatic phasing, encoder alignment and motor-identification routines are hazardous motion tests. Use only the exact manufacturer procedure in a safeguarded environment.

9. Mechanical mounting, coupling and alignment

Verify flange, pilot, shaft, key, coupling, gearbox, belt load, bearing loads, balance, mounting position and fasteners against the exact documentation and machine design.

Do not strike the shaft, use the encoder as a handling point or force a coupling into position. Misalignment, excessive axial or radial load and unsuitable fasteners can damage bearings, feedback systems and mechanical retention.

10. Transport and lifting

Servo motors can be unexpectedly heavy and can have a high centre of gravity. Determine the actual mass and use rated lifting equipment and the manufacturer-approved lifting points.

Protect shafts, connectors, encoders and cooling connections during transport. A dropped or impact-damaged motor must not be installed until its electrical and mechanical condition has been assessed.

11. Temperature, cooling and burn hazards

Motor surfaces, brakes and connected gearboxes can remain hot after operation. Allow the manufacturer-specified cooling period and verify a safe temperature before contact.

Check cooling-air paths, fans, liquid-cooling connections, temperature sensors, ambient temperature, duty cycle and mounting conditions. Missing or incorrect cooling can cause rapid overheating and fire.

12. Inspection and controlled commissioning

Document identity, transport condition, insulation-relevant condition, connectors, shaft and bearings.
Determine and perform the required electrical, mechanical and functional inspections before installation and first use.
Verify mounting, alignment, protective earthing, motor phases, brake, feedback and temperature monitoring.
Begin with the lowest practicable torque, speed and travel in a safeguarded area.
Verify direction, feedback, brake action, temperature response and every affected safety function.
Record the results and release the motor only after all deviations have been resolved.

13. Repair, modification and stop conditions

Opening, rewinding, bearing replacement, brake work, encoder alignment and magnet-related work require a suitable specialist process. Repairs can change insulation, balance, feedback alignment, brake behaviour and safety characteristics.