E-15Â Soft Charge / SCRÂ fault in Toshiba drive
E-15 Soft Charge / SCR Fault fault in Toshiba drive
Description When a VFD first powers up, it must charge its massive DC bus capacitors slowly to prevent blowing the input fuses. It uses a "Soft Charge" circuit (resistors and a bypass relay or SCRs). E-15 indicates that this pre-charge sequence failed. The drive detected that the DC bus voltage did not rise fast enough, or the bypass mechanism failed to close after the charging cycle. Causes
1. Input Phase Loss: If one incoming phase is missing, the capacitors cannot charge fully, triggering E-15.
2. Resistor Open: The ceramic pre-charge resistor is blown (open circuit).
3. Bypass Failure: The contactor or SCR that shorts out the resistor after startup failed to fire.
4. Low Input Voltage: Trying to power a 460V drive on 208V power. Solution Do not cycle power repeatedly. If the pre-charge resistor is damaged, repeated power cycling will cause an arc flash.
Measure the input voltage (L1, L2, L3). It must be within spec.
Listen for the "Click." When you apply power, you should hear a click after 1-3 seconds. This is the bypass contactor. If you don't hear it and then get E-15, the soft charge circuit is broken. On larger drives using SCRs (Thyristors) instead of contactors, check the gate firing board. This usually requires a repair shop intervention as these components are soldered deep inside the power stage.
Description When a VFD first powers up, it must charge its massive DC bus capacitors slowly to prevent blowing the input fuses. It uses a "Soft Charge" circuit (resistors and a bypass relay or SCRs). E-15 indicates that this pre-charge sequence failed. The drive detected that the DC bus voltage did not rise fast enough, or the bypass mechanism failed to close after the charging cycle. Causes
1. Input Phase Loss: If one incoming phase is missing, the capacitors cannot charge fully, triggering E-15.
2. Resistor Open: The ceramic pre-charge resistor is blown (open circuit).
3. Bypass Failure: The contactor or SCR that shorts out the resistor after startup failed to fire.
4. Low Input Voltage: Trying to power a 460V drive on 208V power. Solution Do not cycle power repeatedly. If the pre-charge resistor is damaged, repeated power cycling will cause an arc flash.
Measure the input voltage (L1, L2, L3). It must be within spec.
Listen for the "Click." When you apply power, you should hear a click after 1-3 seconds. This is the bypass contactor. If you don't hear it and then get E-15, the soft charge circuit is broken. On larger drives using SCRs (Thyristors) instead of contactors, check the gate firing board. This usually requires a repair shop intervention as these components are soldered deep inside the power stage.
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