Code boL (Fault): Braking Transistor Overload Fault
Issue Description & Safety Warning
The Yaskawa A1000 AC Drive has triggered a critical Braking Transistor Overload Fault alarm. Immediate attention from a qualified operator or maintenance technician is required to prevent secondary damage to the equipment or spoiled parts during the manufacturing cycle. Always ensure standard safety and LOTO procedures are followed before accessing electrical cabinets.
Official Troubleshooting Steps
Code type: Fault Manual section: Yaskawa A1000 Troubleshooting The wrong braking resistor is installed. Select the optimal braking resistor. Use a regen converter, regen unit, braking unit, or other device to connect the +1 or +3 terminal to the - terminal. Set L8-55 to 0 to disable Internal Braking Transistor Protection. The braking transistor use rate is high (i.e., the regen converter is large or the repetition frequency is high). - Change to a CDBR type braking unit. - Change to a regen converter. - Increase the deceleration time. The braking transistor inside the drive is faulty. Replace the drive.
Source: Yaskawa AC Drive A1000 High Performance Vector Control Drive Technical Manual (SIEP C710616 21H)
Last reviewed: 2026-07-01 · Verified against the manufacturer’s official documentation.
About Yaskawa A1000 AC Drive Alarms
Yaskawa controllers include extensive self-diagnostics that flag or halt the machine when a fault is detected. Error code boL (Fault) on the A1000 AC Drive identifies one specific fault condition — its documented cause and the official corrective steps are listed above, sourced from Yaskawa's service documentation. Always confirm against the manual for your exact machine configuration and follow LOTO procedures before servicing.
Complete Alarm List: 280 Yaskawa A1000 AC Drive codes.
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