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Epsilon Eb and EN Drives Reference Manual
Figure 127: Static Alignment Schematic
The current applied through R to S should be the same polarity each time (i.e., + on R) and
the current must be controlled to no more than 50 percent of the RMS stall current rating of
the motor.
Note
Verify that you are seeing the rising edge of the U channel in the encoder reference
direction by twisting the motor shaft CCW by hand while the DC current is applied and
verifying that U goes high when the shaft is rotated in the encoder reference direction.
Step 4: Determine Motor Parameters
Measuring the actual motor Ke is recommended because not all motor manufacturers use the
same measurement techniques. Normally the number of motor poles and the Ke is specified
on the motor data sheet. If it not, or you wish to verify it, use the following tests.
Motor Ke
In this test you will be measuring the AC voltage generated by the motor or the CEMF
(Counter Electro-Motive Force). This measurement requires an AC voltmeter that can
accurately read sine waves of any frequency and some way to determine the motor speed at
the time of the measurement such as a photo tachometer or an oscilloscope.
1. Connect the volt meter across any two of the motor power leads.
2. Set the volt meter to read VAC at it’s highest range. You can usually expect to read about
20 to 300 VAC.
3. Spin the motor in either direction at least 500 RPM.
4. Determine the actual RPM using a photo-tachometer or by monitoring the frequency of
the Z channel with an ocsilloscope.
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