SIGMATEK AKM Servo Motor Replacement and Troubleshooting Guide

SIGMATEK AKM Servo Motor Replacement and Troubleshooting Guide

In the field of industrial automation, equipment updates and system performance upgrades are the norm that engineers must face. When the original servo motor is discontinued, its performance deteriorates, or it cannot meet the high dynamic requirements of the new generation production line, finding an alternative solution that can perfectly match the original mechanical dimensions and electrical interfaces, while providing higher cost-effectiveness and reliability, becomes the key to the success of the project. The AKM series synchronous servo motors launched by SIGMATEK provide a highly valuable reference solution for the replacement and upgrade of old servo systems, thanks to their rich flange sizes from AKM1 to AKM7, high dynamic response characteristics, and highly flexible feedback and braking configurations.

The core driving force for replacement and selection: why choose the AKM series architecture

When replacing old servo motors, engineers typically face three major pain points: mechanical size mismatch, incompatible feedback systems, and inability to meet modern safety standards. The SIGMATEK AKM series provides highly flexible engineering options for these pain points.

1. Modular mechanical and electrical design

The AKM series synchronous servo motor adopts a brushless rotary converter design, specially designed for high-end servo applications. The rotor is made of neodymium magnet material with high dynamic performance, and the stator is a three-phase winding. Unlike traditional motors, the commutation of AKM motors is completed electronically in servo amplifiers, completely eliminating the hidden danger of brush wear. Its basic structure adopts the IM B5 configuration of DIN EN 60034-7 standard, with flange dimensions in accordance with IEC standards, a fit tolerance of j6 (h7), and accuracy in accordance with DIN 42955 tolerance level N, ensuring seamless replacement with the original gearbox or coupling.

2. Flexible feedback and braking options

When replacing an old motor, the compatibility of the feedback system is of utmost importance. The AKM series comes standard with a passive PTC thermistor (switch point 155 ° C ± 5%) and a rotary transformer (Resolver) as standard feedback units. At the same time, users can flexibly choose between EnDat encoders (single or multi turn, such as ECN 1113, ECN 1125) or HIPERFACE encoders (such as SKM 36) according to the requirements of the servo amplifier. For applications that require vertical axis holding torque, AKM2 to AKM7 models can be equipped with 24V DC spring applied brake. This highly modular design allows engineers to accurately match replacement requirements without changing the original control architecture.

3. Comprehensive compliance and certification

The AKM series motors comply with EG standards 2004/108/EG (electromagnetic compatibility) and 2006/95/EG (electrical equipment within specific voltage limits) and have passed UL certification (E515640). In the replacement project, the use of motors with compliance certification is a prerequisite for ensuring the safety acceptance of the entire machine.

Accurate selection and replacement calculation: avoid "small horses pulling big cars"

When determining the replacement plan, it is far from enough to rely solely on matching the appearance dimensions. The load must be recalculated to ensure that the performance of the new motor meets or even exceeds that of the original system.

1. Core selection parameters

The most important selection criteria include: static torque (M0), rated speed (nn), inertia torque of the motor and load (J), and calculated effective torque (Mrm). When selecting motors and servo amplifiers, both static loads and dynamic loads (acceleration/braking) must be considered simultaneously. The AKM series offers a wide range of choices, such as:

AKM1 series: flange size 40mm, static torque 0.18 to 0.41 Nm, suitable for micro precision equipment.

AKM4 series: flange size 84mm, static torque 1.95 to 6 Nm, suitable for medium-sized universal production lines.

AKM7 series: flange size 188mm, static torque 29.4 to 53 Nm, suitable for heavy-duty high inertia applications.

2. Rigorous environmental derating calculation

When replacing, the impact of ambient temperature on motor performance must not be ignored. According to the technical specifications, the motor needs to undergo a 1% power derating (current and torque) at an ambient temperature between 40 ° C and 50 ° C. If the installation altitude exceeds 1000 meters, it is necessary to reduce the rating according to the altitude: 6% for 2000 meters, 17% for 3000 meters, 30% for 4000 meters, and 55% for 5000 meters. If the altitude exceeds 1000 meters but temperature derating is carried out at the same time (10k derating per 1000 meters), there is no need for further derating. Engineers must calculate the actual working conditions when selecting replacement models to avoid the motor being in an overloaded state for a long time.

3. Rotational inertia and dynamic response

The rotor inertia torque (J) of an AKM motor is an important indicator for measuring its acceleration capability. Taking AKM1 as an example, its J value is only 0.017 to 0.045 kgcm ², which means it can achieve extremely fast acceleration. When replacing an old motor, if the inertia ratio of the new motor is too different from the original system, it may cause difficulty in setting the servo gain and even cause system oscillation. Therefore, it is recommended to control the ratio of load inertia to motor inertia within a reasonable range when replacing calculations.

Guidelines for Avoiding Pits in Mechanical and Electrical Installation

The process of replacing the motor is not simply a matter of "dismantling the old and installing the new". Mechanical installation deviations and electrical wiring negligence can both lead to serious system failures during the debugging phase.

1. The "invisible killer" of mechanical installation: radial force and axial force

Servo motors are precision equipment, and flanges and shaft ends are easily damaged during installation.

Prohibition of violent installation: When installing couplings, gears, or pulleys, it is absolutely forbidden to use brute force to strike. It is necessary to use the threaded holes provided at the motor shaft end, use appropriate tools for pulling, and heat the driving components as much as possible.

Radial force control: If a sprocket or toothed belt drive is used, it will generate higher radial forces. Excessive radial force can significantly shorten the lifespan of motor bearings. When replacing, it is necessary to consult the technical drawings to ensure that the radial force is within the allowable range. When the force is located at the center of the free axis end, the radial force FR may be 10% higher than the nominal value. For toothed belt drive, the minimum allowable sprocket diameter can be determined by the formula

dmin≥(M0/FR)×two 

d min≥(M 0/F R）Calculate by 2.

Axial force limitation: It is advisable to avoid applying axial loads on the motor shaft as much as possible, as axial loads can significantly reduce the service life of the motor.

Installation direction: For V3 installation (axial), it is necessary to ensure that liquid cannot enter the bearing. For special applications that require packaging, the manufacturer's application department should be consulted.

2. Safety of electrical wiring and EMC protection

Safety first: The wiring work of the motor must be carried out by qualified personnel with electrical technology training. Before wiring, it is necessary to ensure that the equipment is in a voltage free state. Even if the servo amplifier is disconnected from the power supply, the intermediate circuit capacitor may still maintain a dangerous high voltage for up to 5 minutes, and the DC bus voltage must be measured until it drops below 40V before it can be touched.

Shielding and grounding: In order to suppress high-frequency noise, prefabricated shielded cables provided by the manufacturer must be used. Power cables and control cables should be routed as separately as possible (spacing>20cm). The shielding layer must be connected to the shielding terminal or EMV plug with a large area and low impedance at both ends (motor side and amplifier side). Incorrect shielding connection can directly cause EMV noise interference.

Connector matching: AKM motors come standard with angled connectors for power and rotary signals. When replacing, it is necessary to check the number of contacts between the motor and the rotary transformer, and set the number of contacts correctly according to the servo amplifier used. Incorrect settings, especially for small motors, may result in motor damage.

Common troubleshooting and debugging guide

After completing the replacement and installation, various exceptions may be encountered during the initial startup phase. The following is a common troubleshooting guide based on engineering practice.

1. Motor does not spin

This is the most common fault in debugging. The investigation directions include:

The servo amplifier is not enabled (ENABLE signal is not applied).

Set value line interruption.

The motor phase sequence is reversed.

The brake is not released (for motors with brake, check if the 24V power supply is normal and if the brake is ventilated).

The driving mechanical part is stuck. It should be checked and corrected one by one.

2. Run away motor

The uncontrolled high-speed rotation of the motor after starting is usually caused by the reverse phase sequence of the motor. This will completely reverse the polarity of the feedback system. The solution is very simple: simply exchange the power lines of any two-phase motor.

3. Motor vibrations

If the motor produces abnormal vibration during operation, it is usually due to the interruption of the shielding layer of the rotary transformer circuit, which causes interference to the feedback signal. In addition, setting the gain of the servo amplifier too high can also cause oscillation. Solution: Replace the well shielded rotary transformer cable or reset the gain using the default parameters of the motor.

4. Brake error message

The servo system indicates a brake failure, which may be due to a short circuit in the brake voltage supply or damage to the brake itself. When troubleshooting, first check if there is a short circuit in the brake power supply circuit. If the circuit is normal, it may be due to damage to the brake coil inside the motor, and the motor needs to be replaced.

5. Error message output stage error

When an amplifier reports an output stage fault, it usually means that there is a short circuit or ground short circuit in the motor circuit. Troubleshooting steps: First disconnect the motor wire, check if the cable insulation is damaged, and replace the cable; If the cable is normal, it may be due to a short circuit or grounding in the internal winding of the motor, and the motor needs to be replaced.

6. Resolver error message

The system prompts a rotary transformer error, which is commonly caused by incorrect connection of the rotary transformer plug or broken or crushed rotary transformer cable. Carefully check whether the plug pins are bent or retracted, use a multimeter to check cable continuity, and replace the rotary cable if necessary.

7. Motor temperature error message

When the motor temperature sensor (PTC) triggers an error, it means that the motor is overheating. Wait for the motor to cool down and investigate the cause of overheating (such as overload, poor heat dissipation). In addition, loose rotary plugs or broken rotary cables may also cause false alarms of temperature signals. Check the connector and install a new rotary cable if necessary.

8. The brakes don't engage

If the brake cannot lock after the motor stops, it may be due to the required stopping torque being too high, exceeding the rated capacity of the brake; Or the brake itself may have been damaged. Mechanical installation should be checked for compliance with requirements. If it is confirmed that the brake is damaged, the motor needs to be replaced.

Debugging checklist and long-term maintenance strategy

1. Initial startup checklist

Before formal operation, please make sure to check according to the following checklist:

Check the installation and alignment of the motor to ensure that the driving components (couplings, gears, pulleys) are securely fastened and set correctly (radial and axial forces within tolerance).

Check the wiring of the motor and servo amplifier to ensure a good grounding connection.

Check if the brake function is normal (apply 24V voltage, the brake should be released by ventilation).

Check if the motor rotor can rotate freely (release the brake first) and listen for any grinding noise.

Ensure that all measures have been taken to prevent contact between moving parts and live parts.

2. Eliminating Interference

In a multi axis system, invisible interference sources may cause system instability. If there are abnormalities during the adjustment process, it is mostly due to incorrect parameter settings in the servo amplifier. You should carefully read the servo amplifier documentation and use debugging software for optimization. In a multi axis system, the mutual interference between each axis also needs to be taken seriously, and if necessary, the manufacturer's application department can be contacted to assist in resolving it.

3. Lifecycle maintenance

The lifespan of servo motors largely depends on the condition of the bearings.

Bearing replacement: Under normal operating conditions, bearings should be replaced after 20000 hours of motor operation (must be carried out by the manufacturer).

Regular inspection: Check the motor every 2500 operating hours or annually and listen for any noise from the ball bearings. If an abnormal sound is heard, the motor cannot continue to operate and the bearings must be replaced.

Warranty warning: It is strictly prohibited to open the motor without authorization. Once the motor is opened, the warranty will immediately become invalid. The maintenance of the motor must be carried out by the manufacturer.

Cleaning and maintenance: When cleaning the casing, isopropanol or similar cleaning agents can be used, but it is strictly prohibited to immerse or spray the motor.