031914 M3-45
SERVO MOTOR POWER VOLTAGE:
The Servo Drive takes a 650 VDC Supply Voltage and
creates a 3 phase AC voltage and frequency to run the
Servo Motors. The Servo Drive controls the speed,
direction and current sent to the motors, based on the
“Speed Command” signal from the Computer. The Servo
Drive monitors and maintains the Servo Motor
performance using Resolver Feedback signals.
(Illustration 61)
FREQUENCY: The Servo Drive uses “Power
Transistors” to change the polarity and frequency
of the voltage sent to the motors. The Transistors
switch the voltage “positive” and “negative,” to
create a 3 phase AC waveform. “Transistor
Switching” allows for a fast response time without
creating a lot of heat. When a Transistor turns
“On,” voltage is immediately sent to the Servo
Motor. There is no change in resistance, so there
is minimal change in temperature. The
“Frequency” of the voltage is controlled by how
fast the Transistors are turned “On” and “Off.”
POWER VOLTAGE: When a transistor turns
“On,” 650 VDC is sent to the motor in the form of
a 3 phase AC waveform. The voltage realized by
the motor, is determined by how long the
Transistor is turned “On,” during the “Frequency”
time. (“Average On Time.”) Power Transistors
send the voltage positive and negative and
create the AC voltage.
CURRENT: Increasing the “On” time of the
Transistors increases the voltage and torque
(current), of the Servo Motor. Increasing the
speed of the “Phase Shifting,” (frequency),
increases the speed of the motor, but decreases
the torque.
SERVO MOTOR POWER CABLES: The Servo Drive
creates a 3 phase AC voltage and sends it to the Servo
Motor on the Motor Power Cable. (Illustration 61) The
Power Cable wires are labeled U, V and W and are
connected to terminals “U2,” “V2” and “W2” on the
Power Cable Plug. These wires must be connected
correctly or the motor will not run. The Power Cable
plugs into the bottom of the Servo Drive and is secured
in place by 2 retaining screws. The Servo Drive must be
removed from the cabinet in order to remove the Servo
Power Cable.
SERVO DRIVES
ILLUSTRATION 61
SERVO MOTOR POWER CABLES
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