First thing to consider in replacing existing servo motors is that there are rarely going to be exact drop-in replacements. Differences in mounting dimensions, performance specifications (torque, speed, rotor inertia), winding or feedback characteristics, connectors and pin-outs, or even overall physical size will likely require some level of re-engineering on the system for the replacement option to be used.
Replacing a motor solely based on paper specs only is problematic at best. Since there is not likely to be another motor that will be a drop-in replacement and have as good or better performance characteristics across the board, you will still end up having to evaluate the application requirements. For example, the replacement motor has enough torque output at roughly the same current level input but has a lower rated speed. Will it work? Depends on whether the application needs that full rated speed the original motor provided.
We recommend treating a replacement opportunity like a new application. Size the application as though there isn't currently a solution for it. After selecting what seems to be a viable solution, you can then compare it against the original solution for differences that will require re-engineering effort on the system as well as to get some confidence that the replacement solution is sized similarly to the original.
We also recommend considering the drive or drive/control solution for upgrade/replacement at the same time. Replacing only the motor will usually require also replacing the cables and standard cables probably do not exist for the new motor to an old legacy drive. New cables can be designed or existing cables modified for the old drive in some cases. However, the drive will also need to be re-configured for the new motor parameters and in many cases some level of re-tuning will be required to achieve the same responsiveness and/or stability as the original solution. Spending the time and money to replace the motor/cables and then have the old drive fail 2-3 months later forcing another re-engineering effort and possibly duplicate costs for another set of cables or modifications can be avoided if the overall system is evaluated for upgrade rather than just the servo motor.
Here are some suggested starting points for replacing various legacy motor lines:
- Z Family Documentation (Z motor information is contained in the user guides)
- APEX Family Documentation (APEX motor information is contained in the user guides)
ML Motor Replacement Options (part of BL/BLX Family)
glh May 2013