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).
4. Clearance Issues: The drive is mounted too close to other heat-generating equipment or lacks the required 4-inch clearance above and below for airflow.
5. High Carrier Frequency: The switching frequency is set too high. Solution Start with a physical inspection. Are the VFD cooling fans spinning? If not, they must be replaced. Toshiba drives usually have replaceable fan cassettes. If the fans are spinning, check the heatsink. If it is covered in dust or fluff, use compressed air (ensure dry air) to blow out the fins from top to bottom.
Check the ambient temperature of the room or cabinet. If the cabinet is hot to the touch, the VFD cannot cool itself. You may need to install cabinet extraction fans or air conditioning. Ensure the VFD is mounted vertically; mounting a VFD horizontally destroys the chimney-effect cooling unless specifically designed for it.
If the physical environment is clean and cool, check the "Carrier Frequency" (PWM Switching Frequency) parameter (often designated as F300). A high carrier frequency (e.g., 12kHz or 15kHz) makes the motor quiet but causes the VFD to generate significantly more heat. Lowering the carrier frequency to 2kHz or 4kHz will drastically reduce the drive's temperature. Note that this will make the motor produce a more audible high-pitched whine, but it often resolves overheating issues immediately without hardware changes.
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).
4. Clearance Issues: The drive is mounted too close to other heat-generating equipment or lacks the required 4-inch clearance above and below for airflow.
5. High Carrier Frequency: The switching frequency is set too high. Solution Start with a physical inspection. Are the VFD cooling fans spinning? If not, they must be replaced. Toshiba drives usually have replaceable fan cassettes. If the fans are spinning, check the heatsink. If it is covered in dust or fluff, use compressed air (ensure dry air) to blow out the fins from top to bottom.
Check the ambient temperature of the room or cabinet. If the cabinet is hot to the touch, the VFD cannot cool itself. You may need to install cabinet extraction fans or air conditioning. Ensure the VFD is mounted vertically; mounting a VFD horizontally destroys the chimney-effect cooling unless specifically designed for it.
If the physical environment is clean and cool, check the "Carrier Frequency" (PWM Switching Frequency) parameter (often designated as F300). A high carrier frequency (e.g., 12kHz or 15kHz) makes the motor quiet but causes the VFD to generate significantly more heat. Lowering the carrier frequency to 2kHz or 4kHz will drastically reduce the drive's temperature. Note that this will make the motor produce a more audible high-pitched whine, but it often resolves overheating issues immediately without hardware changes.
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