Failsafe System Which Uses The Inverter; Precautions For Use Of The Inverter - Mitsubishi Electric 800 Series Instruction Manual

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FAILSAFE SYSTEM WHICH USES THE INVERTER

When a fault is detected by the protective function, the protective function is activated and output a Fault (ALM) signal. However, a fault signal may not be output
at an inverter's fault occurrence when the detection circuit or output circuit fails, etc. Although Mitsubishi assures the best quality products, provide an interlock
which uses inverter status output signals to prevent accidents such as damage to the machine when the inverter fails for some reason. Also, at the same time
consider the system configuration where a failsafe from outside the inverter, without using the inverter, is enabled even if the inverter fails.
 Interlock method which uses the inverter status output signals
By combining the inverter output signals to provide an interlock as shown below, an inverter failure can be detected.
Interlock method
Inverter protective function Operation check of an alarm contact.
operation Circuit error detection by negative logic.
Inverter operating status Operation ready signal check.
Logic check of the start signal and running
Inverter running status
signal.
Logic check of the start signal and output
Inverter running status
current.
 Backup method outside the inverter
Even if the interlock is provided by the inverter status signal, enough failsafe is not ensured depending on the failure status of the inverter itself. For example, if an
inverter CPU fails in a system interlocked with the inverter's fault, start, and RUN signals, no fault signal will be output and the RUN signal will be kept ON
because the inverter CPU is down.
Provide a speed detector to detect the motor speed and current detector to detect the motor current and consider the backup system such as performing a check
as below according to the level of importance of the system.
• Start signal and actual operation check
Check the motor running and motor current while the start signal is input to the inverter by comparing the start signal to the inverter and detected speed of the
speed detector or detected current of the current detector. Note that the current is flowing through the motor while the motor coasts to stop, even after the
inverter's start signal is turned OFF. For the logic check, configure a sequence considering the inverter's deceleration time. In addition, it is recommended to check
the three-phase current when using the current detector.
• Command speed and actual operation check
Check for a gap between the actual speed and commanded speed by comparing the inverter's speed command and the speed detected by the speed detector.
Inverter
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PRECAUTIONS FOR USE OF THE INVERTER

The FR-F800 series inverter is a highly reliable product, but incorrect peripheral circuit making or operation/handling method may shorten the product life or
damage the product. Before starting operation, always recheck the following points.
• Use crimp terminals with insulation sleeves to wire the power supply and the motor.
• Application of power to the output terminals (U, V, W) of the inverter will damage the inverter. Never perform such wiring.
• After wiring, wire offcuts must not be left in the inverter.
Wire offcuts can cause an alarm, failure or malfunction. Always keep the inverter clean.
When drilling mounting holes in an enclosure etc., take caution not to allow chips and other foreign matter to enter the inverter.
• Use an appropriate cable gauge to suppress the voltage drop to 2% or less.
If the wiring distance is long between the inverter and motor, a voltage drop in the main circuit will cause the motor torque to decrease especially during the
output of a low frequency.
Refer to page 10 for the recommended cable gauge.
• Keep the total wiring length within the specified length.
In long distance wiring, charging currents due to stray capacitance in the wiring may degrade the fast-response current limit operation or cause the equipment
on the inverter's output side to malfunction. Pay attention to the total wiring length. (Refer to
• Electromagnetic wave interference
The input/output (main circuit) of the inverter includes high frequency components, which may interfere with the communication devices (such as AM radios)
used near the inverter. In such case, install a noise filter.
Check method
Sensor
(speed, temperature,
air volume, etc.)
To the alarm detection sensor
Used signals
Fault (ALM) signal
Inverter operation ready (RY) signal
Start signal (STF signal, STR signal)
Inverter running (RUN) signal
Start signal (STF signal, STR signal)
Output current detection (Y12) signal
Controller
page 10.)
FAILSAFE SYSTEM WHICH USES THE INVERTER
Refer to
Chapter 5 of the FR-F860
Instruction Manual (Detailed).
Chapter 5 of the FR-F860
Instruction Manual (Detailed).
Chapter 5 of the FR-F860
Instruction Manual (Detailed).
Chapter 5 of the FR-F860
Instruction Manual (Detailed).
System failure
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