Okuma OSP 5000, Electrical Maintenance, Training Manual

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Okuma America Corporation
CONSTR CONSTR
CONSTR CONSTR
CONSTRUCTION UCTION
UCTION UCTION
UCTION
Rev. 8-21-01
It is critical that the sine & cosine signals are 90 degrees out of phase. This can be checked by
looking at CT1 and CT2 on the preamp board. The VR1 potentiometer on the pre-amp board is
adjusted to get the desired POS signal. The desired signal is a steady sinewave anywhere from 6
to 12 Vpp at the POS check terminal. The POS signal is compared to the reference signal. Like
the resolver, the control determines the phase offset between the POS and reference signals and
calculates how much the axis has moved.
Rotary inductosyn transducers work in the same way. Instead of a scale and slider you have a
rotor and stator. Okuma uses inductosyn transducers mostly on machining centers. The data
from the MPR and inductosyn feedback devices are used for positioning purposes.
VAC Resolver
VAC spindle motors have a resolver mounted to it to determine actual motor speed. The control
sends a sine and cosine signal to the stator. The rotor induces a feedback signal. This signal is
7812 hertz when the motor is stopped. The control determines the actual motor speed and
direction by the frequency level of this signal. The frequency can be calculated by using the
following equation:
f = 1/T = 1/(128 x 10-6) ± 8N/60
where N is the motor speed, add in the forward direction, and subtract in the reverse direction.
The motor to spindle speed ratio can be determined by looking in the Operation and Mainte-
nance manual.
Pulse Generators
Okuma uses pulse generators for spindle speed and position feedback. One exception is ma-
chines with Fanuc spindle drives and spindle motors. The Fanuc motor uses an optical encoder
for motor speed feedback. Encoder is a more common name for a pulse generator. Pulse gen-
erators on Okuma machines can be of the optical or magnetic type.
The optical encoder (pulse generator) contains a glass or metallic disk with a number of lines
etched on its surface. The outer row divides one revolution into a specific number of units. The
inner row contains the marker pulse which indicates to the control where to start counting.
Similar to an inductosyn transducer, two signals are generated (A and B phase) by the pulse
generator which are 90° out of phase. These two signals are sent back to the control. The 90°
phase difference for these two signals is how the control determines which direction the pulse
generator is turning. The control monitors the frequency of these signals to determine how fast it
is turning.
The magnetic pulse generator does basically the same thing. Instead of a light source, a rotary