Fadal Baldor Accu-coder Spindle Motor Encoder, ENC-0004

One of the most common problems with a Fadal Spindle Drive running in the Vector mode is caused by the spindle motor encoder. Missing encoder pulses will basically confuse the drive and cause vector miscalculations which result in too much current output to the motor. One sign is that the load meter will usually "peg" or pulsate. Another sign is the RPM will not be stable. Too often the drive is misdiagnosed as being "bad" when it's actually the encoder causing the problem.

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The best method of testing a Fadal Spindle Motor Encoder is to use an oscilloscope to view the A/B channels. Pulse errors can easily be detected. With our new Baldor H2 drive, we simply switch the drive into open loop Inverter mode and you can see the encoder RPM calculations changing erratically with the drives diagnostics feature. With the older Baldor drives, as you rotate the spindle, the drive keypad will display the calculated rpm.

One simple way to manually test an encoder is by using a FLUKE meter, set it to AC input. When checking from the encoder supply power common to one of the A+,A-,B+,B- encoder signals on the spindle drive encoder input terminal, you should see approximately 2.8 VAC when turning the spindle at the orientation speed. The digital pluses look like an AC voltage to a FLUKE meter.

Another important way to test the encoder is by checking the state of each channel. With a voltmeter in the DC setting, from the encoder supply power ground to the A+ encoder input, you should measure either 0 or 3.5 VDC. The state is either high or low. If A+ is high (3.5 volts) then the A- channel must be low; A+ and A- can never be the same. The same logic goes for the B+ and B- channels. If you rotate the spindle and let it stop, you should see the states changing.

Call us for more details about our fadal parts and repair service 1-800-342-3475