July 2013 6.8 The control loop 873
6.8.8 Power and torque limiting
You can limit the power of your spindle motor to achieve wider gear ranges.
Wide-range motors are characterized by a larger speed range with higher
torque at low speed.
One solution for bringing about this behavior is to use an oversized motor, and
to limit the maximum power. However, power limiting does not reduce the
high torque to the speed at which power limiting becomes effective. This high
torque (until power limiting takes effect) can be reduced with torque limiting,
in order to keep the mechanics of the machine from becoming overloaded.
The maximum spindle power will always be limited in order to avoid
overloading the power supply module. If MP2392 is set to zero and a power
supply module is defined in MP2198, the maximum spindle power is limited
to the value S6-40 from the power supply module table (Supply.spy). For
applications requiring a higher spindle power (i.e. the spindle should be able to
take up the maximum power P-Max from Supply.spy), the desired maximum
power must be entered in MP2393.
With torque limiting you can also limit the torque of the axis motors, in order
to keep the mechanics of the machine from becoming overloaded. Power
limiting is not useful for axis motors.
For axes and spindles, the torque is limited to the value taken from either the
table of power modules or the motor table, whichever is lower.
On supply units where the ERR.IZ.GR
signal is available, the power of the
spindle is limited via MP2392.x in case of error (not for axes).
HEIDENHAIN recommends activating this monitoring function via MP2220.x
bit 2 (not with UE 2xx).
The torque can be calculated for any speed:
M: Torque [Nm]
P: Power [W]
n: Speed [min
–1
]
Enter the maximum power for the spindle in MP2392.x.
Enter the maximum torque for the spindle or axis in MP2396.x.
Activate the power limiting of the spindle at ERR.IZ.GR via MP2220.x bit 2 =
0 (not for UE 2xx)
M
P 60⋅
n 2 π⋅⋅
----------------
=
The power and torque limiting can have an effect on the braking of the
spindle in an emergency stop.
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