6 Operation and regulation
82
HSD S.p.A. © - 0106h03a.fm100713
Use and technical characteristics of the thermal alarm
The electrospindle may be fitted with a normally-closed bimetallic strip switch inserted in the
electric windings of the stator which opens when a temperature that may damage the windings is
reached. The contacts re-close when the temperature reduces and returns to the safe values.
The thermal alarm must be connected to the Numerical Control, which should interrupt the
machining operation and stop the rotation of the spindle shaft if the switch opens.
For the bimetallic strip switch connection, see section 4.9 “Electronic connections for models with
free cables”.
Technical characteristics of the bimetallic strip:
PTC Thermistor
In some versions, a PTC thermistor may be inserted into the stator windings to check the
temperature. When the operation temperature has almost been reached (130° C), resistance
increases briskly. This signal must be used by a device which stops the machine to protect the
electrospindle. The operation temperature threshold varies according to the type of electrospindle
(for further information contact the manufacturer's assistance service).
The thermistors used comply with regulations DIN44081-44082.
If the shaft stops while the tool is still being pushed against the piece being
machined, the spindle bearings may break. If the tool is not immediately moved
away from the piece and the rotation stopped, there is a risk of burning out the
stator.
Power supply 48 V
DC MAX
Current 1.6 A MAX
Switching cycles 10000 Cycles
Contact interruption time < 1 ms
Contact resistance (according to MIL R 5757) < 50 m
Isolation voltage 2 kV
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