The emergency stop control circuit has the functions listed below, and
exercises control such that the servo drive power is turned off by hardware
when an emergency stop is required.
1 Control of the servo amplifier MCC (electromagnetic contactor for
turning on/off the motor power line)
2 Control of the brake mounted on each loader axis
These control functions are required to ensure safety. The machine
usually supports similar functions. For the loader also, the machine tool
builder may devise a proprietary circuit to provide the control functions
explained above. An emergency stop control unit that can be used with
the C series servo amplifier is available as an option from FANUC. A
machine tool builder may, however, wish to incorporate the ememergency
stop control circuit into the power magnetic circuit. In such a case,
conform to the specifications given in this section.
The interconnection diagram for an emergency stop system employing a
C series servo amplifier is shown in Subsec. 2.6.2. The signal, *LOT,
from the limit switch for detecting loader overtravel passes through the
emergency stop button on the loader operator’s panel, then drives relay
RY1 in the emergency stop control unit. When external emergency stop
conditions need to be set, a pin, provided before relay RY1, can be used
to insert a contact in series. Jumper the pin when the pin is not required.
Normally, relay RY1 is on. When an emergency stop condition arises,
relay RY1 is turned off, such that contact ry1 turns off the 100 VAC
supply. This loss of the 100 VAC supply turns off the servo amplifier
contactor (MCC), causing the servo drive power to be turned off by the
hardware. At the same time, the 100 VDC supply is also turned off,
turning off the power to, and thus actuating, the brake.
When an α series servo amplifier is being used, the same basic concept
applies. Note, however, that an MCC for controlling the motor power line
and a driving power supply must be installed external to the servo
amplifier, and that an emergency stop contact must be connected to the
power supply module.
Signals to the loader control PMC are transferred through the receiver
circuit, as shown in the diagram. *LOT is the loader overtravel detection
signal, and *EMG1 is the emergency stop signal from the loader
operator’s panel. Note that the circuit is configured such that when *LOT
is turned on, *ESPTP is also turned on. Using a PMC ladder program,
copy *EMG1 to emergency stop input G008.4 of the loader CNC.