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User Defined Motors
Drives can be configured to operate with brushless DC (synchronous permanent magnet)
motors not manufactured by Control Techniques. This feature is very useful for users who are
retrofitting drives on existing systems or who have special motor requirements.
Commutation Basics
To properly commutate the motor, the drive must know the electrical angle (the angle
between the motor magnetic field and stator coils; R, S and T). At power-up, the drive
determines the starting electrical angle from the U, V and W commutation tracks. After this
is determined, the U, V and W commutation tracks are ignored and the commutation is
entirely based on the A and B incremental channels. The number of U, V and W cycles must
match the number of poles in the motor but they do not have to be aligned with the motor
poles in any particular way.
The U, V and W tracks have a fairly coarse resolution, therefore, on power-up, the
commutation accuracy is limited to ±30 electrical degrees from optimum. When the Z
channel is seen by the drive, the commutation angle is gradually shifted to the optimum
position as defined by the Motor Encoder Marker Angle parameter. This shift is accomplished
in about one second whether the motor is rotating or not.
Tools Required:
• Oscilloscope dual trace 5 Mhz bandwidth minimum.
• AC/DC voltmeter, 20 VDC and 200 VAC minimum.
• Drill motor (reversible) or some means of spinning the motor.
• Coupling method between the drill motor and the test motor.
• 5 VDC power supply to power the motor encoder.
• Motor power cable (CMDS or CMMS).
• Motor feedback cable (CFCO).
• Terminal strip (18 position suggested) to conveniently connect the motor power and
encoder wires during testing.
• Method to securely hold the motor during operation (a vise or large C-clamp).
Procedure
The steps required to assemble a servo system consisting of a drive, and a non-Control
Techniques motor are listed below:
Epsilon Eb and EN Drives Reference Manual
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