Posted by Jared Stearns on Thu, Apr 01, 2010 @ 02:12 PM
Are you buying your servo motors from your machine manufacturer and paying way too much money? Have you called the servo motor manufacturer and been told "we cannot sell you this motor, call your OEM"? Before you give up hope, there is a strong possibility you can obtain a replacement motor for much less!
Most OEM servo motors have had modifications made to them specific to their application. These modifications can range from something as simple as connector pin assignments to something as involved as installing special feedback in the servo. In order to determine the modifications made to the motor there are a few pieces of information you need.
Try to obtain a datasheet or brochure on the series of servo motors from the motor manufacturer matching your servo. This will very often give you a rubric to break down you servo motor part number to define the specific properties of your servo. Now you will need the part number off of your motor. Break down your part number using the rubric and see what has been changed. You will find that a letter or number in your part number is not listed as an option in the rubric. That usually corresponds to what is different about your servo. Now for some detective work.
If the change in the part number corresponds to something like a connector or seal you are doing great. Order a servo motor from the servo manufacturer with the closest matching part number and buy the seal or connector separately. Remove the stock seal, connector, etc. and install the unique one and you just saved a lot of money!
Sometimes the part number will have extra characters at the end or the unique sections of the part number will correspond to something complicated such as motor torque or shaft dimensions. Dig deeper into you datasheet, comparing all physical and electrical specifications of your servo to a stock servo, and you should find the modification.
Hopefully you find what makes your OEM servo motor unique and you can be done with drastic overcharging and long lead times by buying your servo motor straight from the manufacturer.
If you need assistance in locating a direct replacement for your OEM servo motor our technicians are here to help! And if a replacement does not exist we are your best source for refurbishing your servo motors to new condition and still avoid overpaying for OEM!
Posted by Jared Stearns on Thu, Feb 04, 2010 @ 05:27 PM
If you ever plan to replace or test a resolver then you need to know the functions of each wire. This can be very difficult to determine with out a little knowledge and a voltmeter. There is an industry standard for resolver wire colors that most manufacturers choose to use. These colors are as follows;
| Wire Color |
Wire Function |
| Red/White |
Excitation + |
| Black/White |
Excitation - |
| Red |
Cos + |
| Black |
Cos - |
| Yellow |
Sin + |
| Blue |
Sin - |
Sometimes Yellow/White can be used in the place of Black/White for Excitation-. These are industry standard wire colors but you will come across other brands of resolvers with their own proprietary color designations. When this happens you will need to use a voltmeter to assist you in determining wire color versus function.
Almost all resolvers have 6 leads. Use a voltmeter to ring out the leads and determine which 3 pairs of wire are circuits. Then record the resistance of each circuit. The
Cos and Sin circuit will have the same resistance, so the circuit with the different resistance will be your excitation circuit. If any circuits ring open, or all three circuits have different resistances then your resolver could have a damaged winding and need to be replaced/rebuilt.
These are some basic tips on how to determine a resolvers wiring. In order to continue on and designate exact wire functions on nonstandard wire colors you will need to excite the windings with the proper frequency and use an oscilloscope.
Posted by Michael Norman on Thu, Nov 05, 2009 @ 07:12 AM
Your servo motor does not have the power it once had. You are starting to encounter current and torque alarms on your machine. You check the couplings, bearings, maybe even swap drives. Nothing seems wrong and the problem is probably in the motor. Now what?
There are several reasons that your servo could be losing torque. Figuring out what is wrong with your motor will determine how difficult it is to fix, and who is even capable of fixing it.
- Does your servo motor have a brake? If there is a brake in your motor then you need to check the voltage going to the brake. Most motors will have the brake voltage written on the label. If the brake is not opened when the motor runs, then you will lose significant torque and also destroy the brake. This is a common problem and is often caused by faulty relays in the cabinet.
- Are your servos magnets demagnetized? This can be determined by checking the BEMF of the servo, which will probably require you to send the motor out to be evaluated. If the servo is demagnetized then you will need to find a company that can re-magnetize your servos' magnets.
- Has your Servo ever been disassembled? If the encoder has been removed and reinstalled the alignment might be off. A bad alignment can cause you servo to run, but run poorly drawing high current. If this is your problem then you need to have your servo serviced and realigned.
Torque Loss is a common problem. The root cause needs to be determined so that you can be sure you are fixing the right problem. If you find you have to send your servo out for repair, it is best to make sure they have the equipment to do the job.
If you don't know what to do or where to have your servo repaired, Servotech has the equipment and knowledge to restore your servo motors torque to its original factory specifications.