(57) A drafting device 11 drives front bottom rollers 12, middle bottom rollers 13, and
back bottom rollers 14 each by two motors: front roller driving motors 16a and 16b,
middle roller driving motors 17a and 17b, and back roller driving motors 18a and 18b.
The driving motors are variable-speed-controlled through inverters 19a, 19b, etc.
, which are provided with current sensors SA. The current sensors SA detect the amount
of electric current supplied in correspondence with the load torques of the driving
motors 16a, 16b, etc. A CPU 31 judges that there is abnormality when the difference
between the load torques of the two motors driving each back roller is deviated from
a set range.
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