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1 Enhanced heat resistance of the motor (Example: When tightening M12 bolts continuously (Cycle of
operation: 5-second impacting and 10-second stopping, 3.0 Ah battery used)
The heat resistance comparison between the Models WH 12DM/WR 12DM and C is shown below. The
Models WH 12DM/WR 12DM are equipped with a powerful motor having 9% larger core diameter, 13% larger
stacking length, 1.4 times thicker winding (2 times larger cross section of the conductor) and 33% larger
volume of the armature than C. The cooling efficiency is improved and the temperature rise is reduced to half
of C (when using two batteries) thanks to the powerful full-fledged large radial fan and the computer-analyzed
air ducts. Thus the Models WH 12DM/WR 12DM are protected from burnout due to long-time continuous use
and decrease in speed due to temperature rise. The motor is manufactured using the latest facilities in
Yamagata Plant.
Temperature
250
200
150
100
50
0
As shown in the above graph, C produces smoke when operating on one battery. When tightening wood
screws (5.3 mm diameter and 120 mm long) into a workpiece (hemlock spruce) continuously, it suddenly takes
much time to tighten the tenth and the later screws. This is because thin wires used in the armature assembly
of C are apt to produce heat and the cooling construction is insufficient to reduce the heat.
C: Smoking
2 batteries
1 battery
Flow of cooling air around the armature
Air inlet
Burnout
C
3 batteries
Large radial fan
--- 5 ---
HITACHI WH 12DM
Air outlet
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