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10. INTERFACE SIGNALS
373
D The zero–speed detection point is 0.75% of the maximum speed
(standard initial setting for the parameter).
In other words, the zero-speed detection signal becomes SSTA = 1
when the rotation speed is 45 min
–1
case of the maximum speed 6000
min
–1
.
D This signal is output when the above condition is satisfied, irrespective
of rotation commands (SFR, SRV).
D The minimum pulse width value of this signal is about 40 ms.
D SDTA = 1 occurs when the motor speed is lower than the speed which
is set by parameter.
D This signal is used to detect that the rotation speed has become lower
than a certain speed set such as clutch selectable speed or gear
selectable speed.
D The speed detecting level can be set by parameter.
It is usually set 3% of the maximum speed in the case of gear change
or 30% of the maximum speed in the case of clutch change.
0
SDTA
1
Speed detection level
1
Motor
speed
Fig.10.2.11 (a) Speed Detection Signal
D For this signal, SDTA = 1 occurs when the absolute value of the motor
speed is reduced to be lower than the preset detection level,
irrespective of rotation commands (SFR, SV).
The gear shift in the CNC machine tool is one of the sequence controls.
The electric circuit signal in the sequence is used to move the spindle gear,
which is an important component of the machine. It is then necessary to
check that the spindle motor revolution is in low speed to switch the gear
safely.
The following is an example of sequence at gear shift, when the speed
detection signal (gear selectable signal) was used. This example can be
referred to when designing the magnetics sequencer.
10.2.11
Speed Detecting Signal
(SDTA)
Reference
D Sequence of the gear
shift