Rockwell Automation LC-Series Linear Motor - Manual (Page 36)

Item Number 814036 - Rev C
3-6 Troubleshooting
Mechanical displacement of one electrical cycle = motor magnetic pitch (180
o
)
in inches multiplied by two. Note that the published specification may already
be in “cycles.” In this case do not multiply by two.
Calculate Back EMF constant:
Note:
Where:
ptz = peak to zero or peak of sinewave
ptp = phase to phase
When comparing to the published Motor Back EMF constant, make sure the
units correspond. Otherwise, convert units accordingly. Consult Anorad
Technical Support if necessary.
Checking the Magnet Plate
Butting Polarity The magnetic plates must be butted such that the magnet polarity sequence is
alternating (north-south) throughout the whole travel. Its is difficult to use the
Back EMF method to check this on motor coils with multiple sets. Analyzing
the trapezoidal Hall effect signal over the whole travel is the best method of
evaluating proper plate polarity.
1. Refer to the Motor Phasing Diagram for expected Hall waveshape.
2. With drive power OFF, verify Hall circuit is connected to the drive per
interface wiring specifications.
3. Disconnect motor leads from drive.
4. Turn Hall power supply ON (driver power ON).
5. Using an oscilloscope, connect one channel between any Hall signal
(output) and Hall signal common.
mechanical displacement of one cycle (inches)
cycle time (seconds)
--------------------------------------------------------------------------------------------------------------- velocity
inches
second
-----------------
[ ]
=
V
ptz
V
pK pK – ( )
0.5 × volts ( ) =
Vptz
Velocity
inches
second
-----------------
--------------------------------------------- Back EMF constant
Voltsptz ptp [ ]
inches
second
-----------------
----------------------------------- =
Voltsptz
ptp [ ]
inches
second
-----------------
-------------------------------- 0.707 × Back EMF constant
VoltsRMS ptp [ ]
inches
second
-----------------
---------------------------------------- =