
B-65222EN/03 CONFIGURATIONS AND SELECTION 2.SELECTION METHODS
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2.4.2 Example of Selection
The cooling unit to be used must has the capacity listed under
"Required cooling capacity" in the specification list in Part I,
"SPECIFICATIONS." This value is determined under the condition
that root mean square force/rated continuous force = 1. Under
ordinary use conditions, the capacity is usually lower than the listed
value. For example, when root mean square force/rated continuous
force = 0.7, the heat output is reduced to 0.7
2
= 0.49 (49%) as
compared with that during continuous operation with the rated
continuous force. For this reason, as the required capacity of the
cooling unit, the value in the specification list can be reduced to 49%.
An example of calculation is shown below:
Assume the following machine:
- X-axis:
One 9000B/4, water cooling, root mean square force/rated
continuous force = 0.7
- Y-axis:
One 3000B/4, water cooling, root mean square force/rated
continuous force = 0.8
Because the cooling capacity required for the X-axis (9000B/4) is
2,600 W as listed in Section 1.2, "SPECIFICATION LIST," in Part I,
"SPECIFICATIONS," the required cooling capacity under the above
condition is:
2,600[W]×0.7
2
=1,274[W]
Similarly, the cooling capacity required for the Y-axis (3000B/4) is:
900[W]×0.8
2
=576[W]
Consequently, if the motors on both the X-and Y-axes run
simultaneously, the maximum required cooling capacity is:
1,274[W]+576[W] =1,850[W]
If the motors on both the X-and Y-axes do not run simultaneously, the
required cooling capacity is 1,274 [W].
To determine the required cooling capacity more precisely, it is
advisable to add the duty curves (root mean square force/rated
continuous force) for both axes based on the time axis and calculate
the cooling capacity at the point where the sum is the maximum.
NOTE
1 For how to calculate the root mean square force, see Part II, "CONFIGURATIONS
AND SELECTION."
2 The cooling capacity calculated as above is required when the internal temperature
of the coil slider rises to a temperature near the maximum operating temperature. For
this reason, if the machine is apt to be easily deformed by temperature rising, it may
be desirable to select a cooling unit with an adequate margin of the required cooling
capacity.
3 Use of strong cooling can increase the rated continuous force of the motor to some
extent. Carefully use strong cooling so that condensation does not occur on the coil
slider due to excessive cooling.