Posts

Featured Post

OC (OC1, OC2, OC3) Overcurrent fault in Toshiba drive

-
OC (OC1, OC2, OC3) Overcurrent During Acceleration, Deceleration, or Constant Speed fault in Toshiba drive Description The Overcurrent (OC) fault is the most frequent trip in variable frequency drives. It indicates that the output current going to the motor has exceeded the drive's rated current capacity, typically by 200% or more, for a split second. The drive shuts down the output transistors (IGBTs) instantly to protect the hardware from catastrophic failure. OC1 occurs during acceleration, OC2 during deceleration, and OC3 during constant speed operation. Understanding which phase the drive was in is crucial for diagnosis. This is not a thermal overload (which is slow); this is an instantaneous spike in amperage. Causes 1. Short Circuit: A phase-to-phase short in the motor windings or output cabling. 2. Ground Fault: A phase-to-ground short, often caused by damaged cable insulati...
Post a Comment
Read more

OP (OP1, OP2, OP3) Overvoltage (DC Bus) fault in Toshiba drive

-
OP (OP1, OP2, OP3) Overvoltage (DC Bus) fault in Toshiba drive Description The Overvoltage (OP) fault indicates that the DC bus voltage inside the drive has exceeded the safety threshold (typically around 400V for 230V class drives, or 800V for 460V class drives). The DC bus is the energy reservoir of the drive. This fault can happen when the drive is stopped (due to input spikes) but most commonly occurs during deceleration (OP2). When a motor decelerates, it acts as a generator, sending energy back into the drive (regeneration). If the drive cannot absorb or dissipate this energy, the voltage rises until it trips. Causes 1. Deceleration Time: The DEC time is too short. The drive is trying to stop a heavy load faster than the regenerative energy can be dissipated. 2. High Input Voltage: Power surges or capacitor switching at the utility level causing spikes on the input lines. ...
Post a Comment
Read more

OL1 / OL2 Motor Overload / Drive Overload fault in Toshiba drive

-
OL1 / OL2 Motor Overload / Drive Overload fault in Toshiba drive Description OL faults relate to thermal capacity. OL1 is the "Electronic Motor Thermal Protection" calculation, meaning the VFD calculates that the motor is running too hot based on the current draw over time. OL2 indicates the VFD internal components (heatsink/IGBTs) are thermally overloaded. This functions similarly to a traditional bimetallic overload relay but is calculated digitally. The trip curve is inverse-time: the higher the current, the faster it trips. It protects the insulation of the motor from melting. Causes 1. Excessive Load: The motor is physically doing more work than it is rated for (e.g., dull cutting blades, clogged filters, worn bearings). 2. Low Speed Operation: Running a standard AC induction motor at very low speeds (below 30Hz) without a cooling fan. The shaft-mounted fan does not spin ...
Post a Comment
Read more

OH (OH1, OH2) Heatsink Overheat fault in Toshiba drive

-
OH (OH1, OH2) Heatsink Overheat fault in Toshiba drive Description The OH fault signifies that the variable frequency drive's own temperature sensor (located on the heatsink near the IGBT modules) detects a temperature exceeding the safe limit (usually around 85°C to 95°C). While OL2 is a calculated overload based on current, OH is a physical temperature measurement. If the drive gets too hot, the semiconductor life is drastically reduced, or they may explode. The drive shuts down to cool itself. Causes 1. Cooling Fan Failure: The most common cause. The cooling fans on top or bottom of the VFD have stopped working or are clogged. 2. Blocked Ventilation: The heatsink fins are clogged with dust, lint, or oil mist, preventing air heat exchange. 3. High Ambient Temperature: The electrical cabinet is too hot (summer conditions or lack of cabinet AC/ventilation)...
Post a Comment
Read more

EF (EF1, EF2) Earth Fault / Ground Fault fault in Toshiba drive

-
EF (EF1, EF2) Earth Fault / Ground Fault fault in Toshiba drive Description An EF fault occurs when the drive detects current leakage from the output phases to the earth (ground). The drive uses a Zero Phase Sequence Current Transformer (ZCT) or software calculation to sum the currents of U, V, and W. Under normal conditions, the sum should be zero. If current leaks to the ground, the sum is non-zero. This is a critical safety fault indicating damaged insulation. Resetting this fault repeatedly without fixing the cause will destroy the drive. Causes 1. Motor Insulation Failure: The varnish on the motor copper windings has burned off, shorting to the motor stator/frame. 2. Cable Damage: The output cable insulation has been chafed, cut, or soaked in water (conduit flooding). 3. Moisture: Water ingress in the motor terminal box or the VFD terminal strip. ...
Post a Comment
Read more

EPH (EPH1, EPH0) Input Phase Failure fault in Toshiba drive

-
EPH (EPH1, EPH0) Input Phase Failure fault in Toshiba drive Description EPH indicates that one of the three input power phases (R, S, T / L1, L2, L3) is missing or has a significant voltage imbalance. The drive monitors the ripple on the DC bus. If a phase is lost, the DC bus ripple increases drastically. Running on a single phase puts extreme stress on the input rectifier bridge and capacitors, so the drive trips to prevent hardware explosion. Causes 1. Blown Fuse: A fuse on the main distribution panel or disconnect switch has blown on one phase. 2. Loose Connection: A wire is loose at the input terminal block of the drive or the breaker. 3. Contact Failure: A magnetic contactor feeding the drive has pitted or burnt contacts that aren't conducting on one pole. 4. Grid Failure: The utility company has dropped a phase (common in rural...
Post a Comment
Read more

UP (UP1) Undervoltage Protection fault in Toshiba drive

-
UP (UP1) Undervoltage Protection fault in Toshiba drive Description UP indicates the DC bus voltage has dropped below the operational floor. The VFD logic circuits (the "brain") run off a switched-mode power supply fed by the DC bus. If the voltage drops too low, the brain will die. The UP fault is a warning that power is insufficient to maintain motor torque. This usually happens when the main power is cut, but if it happens while running, it's a problem. Causes 1. Brownout: The facility voltage has sagged significantly (e.g., heavy machinery starting nearby). 2. Contactor Issues: A pre-charge contactor inside the drive (or external) failed to close, or contacts are bouncing. 3. Internal Circuit Failure: The "Soft Charge" resistor or relay inside the drive has failed. 4. Loose Input Wiring: High resistance connec...
Post a Comment
Read more