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Servo Motor & Cable Selection

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What things to consider in selecting Servo Motor and Cable for Servo Upgrade.

Like in many case, because existing Servo already obsolete, no spare available or need higher precision motor, it could be decided to upgrade it to newer servo. Let say to Allen Bradley / Rockwell Kinetix series.

When we want to upgrade existing Motion Control, several data need to be collected. As if not checked and ignored , it will end up that the motor and cable that has been ordered and waited for long time , can not be used at all.

Here is the things that need to be checked to get right servo motor and cable:

𝐌𝐨𝐭𝐨𝐫 𝐓𝐨𝐫𝐪𝐮𝐞
If the new Motor Rated Torque is too low, the motor will have not enough torque to move the load and can result on ‘position error fault ‘ or other fault.

𝐈𝐧𝐞𝐫𝐭𝐢𝐚 𝐨𝐟 𝐍𝐞𝐰 𝐌𝐨𝐭𝐨𝐫.
If the inertia of new motor is too high or to low ,the new motor can oscilate, unstable, have reduced accuracy or draw eccessive current.

𝐌𝐚𝐱𝐢𝐦𝐮𝐦 𝐒𝐩𝐞𝐞𝐝
If Maximum Speed of new motor is lower than requirement, the machine can not achieve target speed.

𝐁𝐫𝐚𝐤𝐞 𝐑𝐞𝐪𝐮𝐢𝐫𝐞𝐦𝐞𝐧𝐭
If brake required, but new motor don’t have brake, the motor can not keep in place when servo / power off.

𝐒𝐩𝐚𝐜𝐞 𝐟𝐨𝐫 𝐍𝐞𝐰 𝐌𝐨𝐭𝐨𝐫
Make sure enough space to install the new motor , especially If the new motor is bigger than existing.

𝐅𝐨𝐨𝐝 𝐆𝐫𝐚𝐝𝐞 𝐌𝐨𝐭𝐨𝐫 𝐫𝐞𝐪𝐮𝐢𝐫𝐞𝐦𝐞𝐧𝐭
Certain places like in food & beverage need the servo motor to be food grade

𝐒𝐮𝐫𝐫𝐨𝐮𝐧𝐝𝐢𝐧𝐠 𝐄𝐧𝐯𝐢𝐫𝐨𝐦𝐞𝐧𝐭
Check whether the surrounding is not damp or humid and cause water to get into and damage servo motor bearing. Shaft seal maybe required.

𝐌𝐨𝐮𝐧𝐭𝐢𝐧𝐠 𝐚𝐧𝐝 𝐒𝐡𝐚𝐟𝐭 𝐃𝐢𝐦𝐞𝐧𝐬𝐢𝐨𝐧
Check whether mouting adapter can be made. Too small shaft diameter and longer shaft can degrade the perfomance of new motor too.

𝐅𝐥𝐞𝐱 𝐌𝐨𝐭𝐨𝐫 𝐂𝐚𝐛𝐥𝐞 𝐑𝐞𝐪𝐮𝐢𝐫𝐞𝐦𝐞𝐧𝐭
If the motor cable is moving during operation, make sure to select flexible motor cable instead standard one. As the movement on cable can easily break the non flexible cable over the period of time ( Typical it will break the motor feedback cable less than a year, depend on movement intensity)

𝐌𝐨𝐭𝐨𝐫 𝐂𝐚𝐛𝐥𝐞 𝐃𝐢𝐬𝐭𝐚𝐧𝐜𝐞
Check cable distance . As we don’t want the new cable shorter and can not connect the servo drive to the motor.

𝐌𝐨𝐭𝐨𝐫 𝐅𝐞𝐞𝐝𝐛𝐚𝐜𝐤 𝐓𝐲𝐩𝐞
Check existing motor feedback. What is the type of existing encoder used? Is it incremental or absolute feedback? Use of lower resolution encoder sure will decrease the accuracy of servo control.

𝐌𝐨𝐭𝐨𝐫 𝐕𝐨𝐥𝐭𝐚𝐠𝐞
Be aware that Allen Bradley Servo Motor has 2 operation voltage. That is 200V and 400 V . This is also depend on Servo drive that chosen.

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