Mitsubishi Electric FR-D700 Basic Inverter

A voltage (or current) has been incorrectly applied to terminal 4 due to a mismatch between the Pr. 267 Terminal 4 input selection setting and the physical voltage/current input switch position. This incorrect configuration can lead to erroneous frequency commands, inaccurate control, or potential damage to the inverter's analog input circuitry.

An error has occurred within the inverter's Central Processing Unit (CPU) or its associated peripheral circuits. This is a critical internal hardware or software issue, potentially leading to a complete loss of control and unpredictable inverter behavior. Continued operation or neglect may result in further hardware damage or system unresponsiveness.

The analog input bias and gain calibration values (C3, C4, C6, and C7) have been set too closely, indicating a potential configuration issue with the analog input scaling. This can lead to inaccurate sensor readings, incorrect frequency commands, or unreliable control signals, affecting overall system performance.

The cumulative thermal value of the electronic thermal O/L relay has reached 85% or higher of the Pr. 9 (Electronic thermal O/L relay) setting. This indicates that the motor or inverter is approaching its thermal overload limit. Continuing operation without intervention will almost certainly lead to an electronic thermal overload trip, shutting down the inverter.

The external thermal relay connected to the OH signal has been activated, indicating an overload or excessive temperature condition. This protective function safeguards the motor/system from overheating and potential damage. If left unresolved, it can lead to motor failure or premature component wear.

The cooling fan is either at a standstill despite being required to operate, or its speed has significantly decelerated, indicating a malfunction. The cooling fan is essential for dissipating heat from the inverter. Without adequate cooling, the inverter will overheat and trip, potentially leading to irreversible component damage.

The resistor within the inrush current limit circuit has overheated, often as a result of frequent power ON/OFF cycles. This circuit is vital for protecting the inverter's main circuit from high currents during power-up. Overheating indicates a potential failure of this component, risking significant damage to the inverter's power stage.

The reset signal (RES signal) has been activated, causing the inverter output to shut off. This indicates a system reset command was issued, either manually by an operator or automatically due to certain internal conditions. The inverter will remain in a reset state until the command is cleared.

The cumulative energization time of the inverter has exceeded the set value in the maintenance output timer (Pr. 503). This is a reminder or pre-alarm indicating that periodic maintenance is due, based on accumulated operational hours. It is not a fault but a preventative warning, suggesting that routine checks are required.

Parameter setting was attempted in External or NET operation mode when Pr. 77 (Parameter write selection) was not '2', or parameter writing was attempted when the command source was not the operation panel. This prevents modification of parameters under specific operating conditions to maintain system integrity and prevent unintended changes.

An attempt was made to operate the inverter while the operation panel was in a locked state, preventing parameter changes or control actions. This is often a security or accidental lockout feature designed to prevent unauthorized modifications. The inverter will not respond to panel inputs until unlocked.

The inverter's output current has surpassed the configured detection level, which is set via specific parameters. This typically indicates an overload condition on the motor or an incorrect configuration of the current monitoring parameters. Operating continuously at excessive current levels risks damaging the motor, inverter components, or the connected load.

The resistance of the PTC thermistor, connected between terminals 2 and 10, has exceeded the set protection level (Pr. 561). This signifies that the monitored motor or component is overheating. Continuing operation under this condition poses a high risk of severe motor damage.

A communication error has occurred between the Parameter Unit (PU) and the inverter, or the communication interval has exceeded the permissible time during RS-485 communication. This prevents proper control, monitoring, and parameter adjustment of the inverter. Risk includes loss of operational control and inability to make necessary system adjustments.

The [STOP] key on the operation panel of the Parameter Unit (PU) was pressed during External operation. This indicates a manual stop command was initiated from the PU while the inverter was configured for external control, causing the inverter to cease operation.

The component responsible for storing parameters (typically on the control circuit board) has become abnormal, indicating a potential hardware or firmware issue. This fault can lead to incorrect operation, loss of configured settings, or general system instability. Unresolved, it risks unpredictable behavior or complete system failure.

An attempt was made to read or write a parameter that is restricted by a password, preventing access or modification. This security feature protects critical parameters from unauthorized changes, ensuring system integrity and safety. Access is denied until the correct password is provided.

The regenerative brake duty cycle has reached 85% or higher of the Pr. 70 (Special regenerative brake duty) setting. This is a warning that the inverter's regenerative braking capacity is nearing its thermal limit. Continuous operation at this level can lead to an overvoltage fault, damage to internal components, or overheating of the braking resistor if one is installed.

The inverter failed to restart or clear a fault within the configured number of retries after a preceding error. This indicates that the underlying problem persists, and the automatic retry mechanism could not resolve it. Ignoring this fault means the primary cause of the trip is still active, potentially leading to continued downtime or further damage.

The safety stop function has been activated, resulting in an immediate shutdown of the inverter outputs. This critical safety measure is typically triggered by an external safety device or a wiring issue across terminals S1 and SC, or S2 and SC, indicating an open circuit in the safety chain. If misconfigured or experiencing an internal failure, it can prevent normal operation or compromise machinery safety.

The overcurrent stall prevention function has been activated, meaning the inverter detected conditions that could lead to motor stall due to excessive current draw. This protective feature safeguards both the motor and inverter from damage. If ignored, persistent overcurrent can lead to motor overheating, winding damage, or inverter component stress.

The overvoltage stall prevention function has been activated, often occurring during regenerative braking or deceleration. This indicates that the DC bus voltage within the inverter is rising to an excessively high level, threatening to damage internal components. This protection ensures the inverter remains within safe operating voltage limits.

The voltage at the main circuit power supply has dropped below an acceptable operating level. This can be caused by issues in the power supply line, such as voltage sags, power supply capacity problems, or faulty connections. Sustained undervoltage can lead to unreliable inverter operation, internal component stress, or even damage.

Parameter setting was attempted while parameter writing is set to be disabled, or an overlapping range has been configured for frequency jump parameters (Pr. 31 to Pr. 36), or normal communication between the PU and inverter is compromised. This prevents parameter changes, hindering proper configuration or commissioning.

A parameter writing attempt was made while the STF (STR) signal was ON (indicating operation) and Pr. 77 (Parameter write selection) was not set to '2' (which allows writing during operation). This protection mechanism prevents critical parameter changes during active inverter operation, which could lead to unsafe conditions or system instability.