Selection criteria
SELECTING CRITERIA
Asynchronous spindle motor and servo drive selection
5.
211
DDS
HARDWARE
Ref.1310
5.2 Asynchronous spindle motor and servo drive selection
On the spindles of machine tools, it is important to maintain a constant
turning speed of the spindle. To control this speed, the drive applies
torque to the load according to the characteristics of this load as well as
to the adjusted accelerations and decelerations.
Procedure to calculated the needed motor power:
1. Depending on the characteristics of the load, determine the rated val-
ues of the needed power (in continuous cycle, instantly and periodical-
ly).
2. Increase the value of that needed power, considering the efficiency of
the power transmission and load dispersion.
3. Select the drive that offers the current needed to govern the motor in
all duty cycles for that machine.
Power demanded from a motor for a particular load
To determine the needed motor power, use the following formula:
The power of the motor must be greater than the sum of the power re-
quired by the load and the power required by the machine's accelerations
and decelerations.
Power required by the load
The power demanded from an asynchronous spindle motor in a turning or
machining center is determined by the cutting power.
A good cutting process required the asynchronous spindle motor to be
working at constant power and with a power range between 1:3 and 1:5.
The power values used for a cutting operation on a lathe, mill or machin-
ing center with a drill are calculated using the following formulas.
For a more accurate calculation of the power required, one must bear in
mind different factors such as cutting oil, material, shape of the tools,
hardness of the material machined, etc.
F. H5/2
Constant power required from the motor for a load regardless of the load.
T. H5/1 Constant motor power demanded by a load.
Constant motor power
Load type
Constant power, regardless of speed
Examples Winding machines at constant tenstion
Milling spindle
Lathe spindle
Torque/speed
characteristics
The torque decreases from base speed on
Motor Power
The rated power of the drive will be the one
demanded by the load.
P
MOTOR
P
LOAD
P
ACCEL/DECEL
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