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ocA Over-Current during Acceleration fault in delta drive

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ocA Over-Current during Acceleration fault in delta drive troubleshooting Description The ocA fault indicates that the output current of the Variable Frequency Drive (VFD) has exceeded the rated current limit (typically 200% to 300% depending on the model) specifically during the acceleration ramp-up phase. This implies that as the drive attempts to increase the frequency to speed up the motor, the load or a system defect is drawing excessive amperage instantaneously. Causes The primary causes for an ocA fault generally fall into three categories: parameter settings, mechanical load, or electrical shorts. 1. Acceleration Time too Short: If the acceleration time (Parameter 01-09 or similar) is set too low, the drive attempts to overcome the inertia of the motor and load too quickly, requiring massive current. 2. Short Circuit or Ground Fault: There may be a p...
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ocd Over-Current during Deceleration fault in delta drive

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ocd Over-Current during Deceleration fault in delta drive troubleshooting Description The ocd fault signifies that the output current exceeded the drive’s safety threshold while the motor was slowing down (decelerating). This differs from acceleration faults because it is often linked to regeneration energy and the drive fighting against the motor's kinetic energy to bring it to a stop. Causes When a motor is forced to stop faster than it naturally would (coasting), it acts as a generator. However, an Over-Current during this phase usually means the drive is trying to impose a frequency change that results in a high current slip. 1. Deceleration Time too Short: The drive is trying to force the motor to zero speed too aggressively. 2. External Force: A load (like a fan in a draft or a downhill conveyor) is driving the motor faster than the VFD frequency...
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ocn Over-Current during Constant Speed fault in delta drive

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ocn Over-Current during Constant Speed fault in delta drive troubleshooting Description The ocn fault occurs when the drive detects an over-current condition while the motor is running at a steady, constant speed. This is arguably the most problematic of the OC faults because the system is supposed to be in a stable state, implying a sudden change in conditions. Causes Sudden spikes in current during steady operations are usually external: 1. Sudden Load Change: A jam in a conveyor, a sudden blockage in a pump, or a mechanical binding in a gearbox can instantly spike torque demand and current. 2. Insulation Breakdown: As the motor heats up during operation, weak insulation might fail, causing an intermittent arc/short that triggers the protection. 3. Loose Wiring: Vibrations at constant speed might cause a loose connection to arc, creatin...
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ovA Over-Voltage during Acceleration fault in delta drive

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ovA Over-Voltage during Acceleration fault in delta drive troubleshooting Description ovA indicates that the DC bus voltage inside the VFD has exceeded its maximum limit (e.g., 410V for 220V class, 820V for 440V class) while the drive was accelerating. This is a less common fault than over-current during acceleration but points to specific power supply issues. Causes 1. Input Voltage Surge: The mains power supply might have spiked. If using a capacitor bank for power factor correction on the main grid, switching it on can cause voltage swells. 2. Restarting a Spinning Motor: If the VFD attempts to accelerate a motor that is already spinning (windmilling fan), the back EMF generated by the motor can sum with the drive voltage, causing a DC bus spike. 3. Peripheral Hardware: Incorrectly wired braking units or faulty internal capacitors. S...
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ovd Over-Voltage during Deceleration fault in delta drive

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ovd Over-Voltage during Deceleration fault in delta drive troubleshooting Description The ovd fault is the classic "Regeneration" fault. It occurs when the DC bus voltage rises too high while the motor is slowing down. This is the most common over-voltage fault and is directly related to the physics of kinetic energy. Causes When an AC motor is mechanically driven faster than the synchronous frequency set by the VFD (which happens when you lower the frequency to stop), the motor acts as a generator. This "Regenerative Energy" flows back into the drive. The drive's rectifiers block it from going back to the grid, so it accumulates in the DC bus capacitors, raising the voltage until it trips. 1. Decel Time too Short: Trying to stop a heavy flywheel or high-inertia load too fast. 2. No Braking Resistor: The energy has nowhere to go. ...
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ovn Over-Voltage during Constant Speed fault in delta drive

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ovn Over-Voltage during Constant Speed fault in delta drive troubleshooting Description ovn indicates the DC bus voltage is too high while the motor is running at a set speed. Since there is no deceleration occurring, regeneration shouldn't technically happen, making this fault indicative of input power or specific load types. Causes 1. Input Voltage High: The facility's transformer tap might be set too high, or there is unstable grid power. 2. Overhauling Load: If the load pushes the motor (e.g., a downhill conveyor belt or an elevator going down with a heavy load), the motor runs faster than the drive command, generating energy continuously. 3. Capacitor Issues: The drive's internal DC bus capacitors may be degrading, causing voltage ripple that is interpreted as peak over-voltage. Solution Focus on th...
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Lv / LvA / Lvd Low Voltage fault in delta drive

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Lv / LvA / Lvd Low Voltage fault in delta drive troubleshooting Description The Lv (Low Voltage) fault triggers when the DC bus voltage drops below a minimum threshold (e.g., < 190VDC for a 220V class drive). This ensures the IGBTs have enough voltage to gate properly and prevents the control electronics from shutting down unexpectedly. Causes 1. Input Phase Loss: One of the three input phases (R, S, T) is missing or a fuse has blown. The drive might run on single phase under light load but will trip Lv under load. 2. Low Mains Voltage: Brownouts or voltage sags in the facility. 3. Contactor Failure: The internal "Charge Relay" or contactor that bypasses the soft-charge resistor may have failed. If this doesn't close, the voltage drops immediately when the motor starts. 4. Sudden Load: A massive starting current draw on ...
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