Before repairing Emerson series inverters, it is essential to understand the fault code. Without this knowledge, you won't be able to start the device properly.
Fault Code Fault Type
POFF - Input undervoltage
E001 - Accelerated overcurrent
E002 - Deceleration overcurrent
E003 - Constant speed overcurrent
E004 - Accelerated overvoltage
E005 - Deceleration overvoltage
E006 - Constant speed overpressure
E007 - Control power supply overvoltage
E008 - Input phase loss
E009 - Output phase loss
E010 - Module protection
E011 - Inverter overheating
E012 - Rectification overheating
E016 - Read and write fault
E018 - Contactor not sucking
E019 - Current detection circuit failure
1. Current Detection Fault (e.g., E019, E001)
(1) The control board Q1 (15050026) may be faulty.
(2) 7840 IC could be damaged. When the inverter is powered on, use a DC meter: connect the black lead to pin 5, and the red lead to pins 6, 7, and 8 respectively. If the readings are 2.5, 2.5, and 5, it's normal. Otherwise, the 7840 is faulty.
(3) The small board may be bad. When the inverter is energized, check the voltage from pin 5 of the 7840 to the small board. The expected values should be around 2.5, 2.5, 2.5, 3.4, 1.5, 0, and 1.6 from left to right. If any value is off, the small board is likely faulty. Replace the three small ICs (39030024 LMV393). If the issue persists, replace the small board entirely.
2. Display POFF
Check the CVD voltage on the drive board; it should be 2.6–2.7 V. If it reads 1.9 V, one of the components such as R51, R52, C36, or C37 may be faulty, especially the electrolytic capacitor. POFF occurs only when the motor is running, and the driver board transformer might be damaged.
3. Buffer Resistor Fault
A faulty buffer resistor often indicates that the filter capacitor is also damaged. A relay that doesn’t engage can also cause issues. For single-phase input (220V) inverters, if there’s no display or a "bomber" sound, the user may have connected it to a three-phase system (380V). Check the bus voltage on the control board: if it changes from 310 V to 540 V, the rectifier bridge and filter capacitor may be damaged. Replacing the IPM without checking the capacitor can cause another failure. If the capacitor is swollen or hardened, it must be replaced immediately.
4. Unstable Display
If the display flickers or turns off, and the fan stops with only 12 V, the U1 thick film is likely faulty. If E015 appears, the power-on indicator is on, but the keyboard is unresponsive and the fan runs slowly—this could indicate a shorted fan. For braking issues, check the brake tubes (01180100, 01180113, 01180114) inside the IPM. After replacing the IPM, verify the brake circuit, including the optocoupler and MOS tube. Measure the MOS tube’s gate resistance (should be around 100 Ω) and its freewheeling diode (around 0.37 V). If the brake voltage is between 17–30 V (TD900 F093 = 150), it’s functioning properly.
5. Damaged Rectifier Bridge
If some rectifier bridges are damaged while others are intact, it may be due to sparks between the positive and negative busbars. High humidity is often the cause, leading to water droplets between terminals. Insulation degradation requires replacement. Another cause is a short-circuited filter capacitor (swollen or hardened), which must be replaced to avoid repeated failures.
6. Machine Hiccup
This refers to a fast-slow fan with no display. It usually indicates a short-circuited control board. Remove the board and power it on again. If the problem remains, check for damaged components near the thick film, such as a resistor (e.g., R56 on TD1000) that has increased significantly. If the switching power supply isn’t working, check for short circuits in the rear circuit or between the transformer pins. If there’s no voltage at all, the thick film or nearby components like 2844 may be faulty.
7. Weak Fan Speed
For EV1000 D6, a breakdown may occur. For FECDF21U1 boards, U8 may be damaged with visible cracks. If the load stops and reports 8888, it could be due to poor inductance in the transformer or insufficient insulation between primary and secondary coils of PC9.
8. Fault Report 8888
It may indicate a shorted drive optocoupler.
9. EV1000 Large Volume
The original fault was a bomber, followed by no output or E019. U9 is often the culprit. Sometimes Q2 is faulty. No output can also point to a damaged Q2.
10. EV1000 Small Volume
After repair, if there’s no output, R13 is likely damaged. Always check if R13 is 10 ohms before proceeding with repairs.
11. General Notes
Inverters consist of the main circuit, power circuit, IPM drive and protection circuit, cooling fan, and more. Their modular design makes them prone to issues from incorrect use or environmental factors. To prevent problems, it’s crucial to analyze the root causes of faults thoroughly.
1.1 Common Main Circuit Faults
The main circuit includes rectifier bridges, smoothing capacitors, filter capacitors, IPM bridges, current limiting resistors, and contactors. Many of these issues stem from electrolytic capacitors. Their lifespan depends on the applied voltage and internal temperature. Capacitors are designed to last, but high temperatures reduce their life. Every 10°C increase halves the lifespan. Ensure proper ambient temperature and consider using reactors to reduce ripple current. During maintenance, check the capacitance (should be above 80% of rated value) and insulation resistance (≥5 MΩ). If either is low, replace the capacitor.
1.2 Typical Main Circuit Failures
Symptom: Overcurrent during acceleration, deceleration, or normal operation. First, determine whether the issue is with the load or the inverter itself. If the inverter trips, check the current against the rated value. If balanced, consider overload or sudden motor stall. Adjust acceleration time to prevent damage. If the current is within limits, the IPM module or related components may be faulty. Test the resistance between P/N and U/V/W. If the module is fine, the drive circuit is likely the issue. Upper IPM faults during deceleration, lower during acceleration. External dust or humidity often causes these issues.
1.3 Control Loop Failure Analysis
The control loop affects the inverter’s lifespan, particularly the power supply, smoothing, and snubber capacitors. These capacitors are soldered, making visual inspection difficult. Estimate lifespan based on temperature and usage time. Power supplies provide power to the control loop, IPM drive, display, and fan. A short in one power supply can affect others. For example, a control power short can damage the switching power supply. Logic control boards (with CPU, MPU, etc.) are reliable but may fail due to EEPROM issues after power-on. IPM boards contain drive and buffer circuits. Check optocouplers for faults.
1.4 Cooling System
The cooling system includes heat sinks and fans. Fans have limited lifespans, typically 10,000–35,000 hours. As they age, vibration increases, noise grows, and eventually, the fan stops. This leads to IPM overheat tripping. To extend fan life, some models operate only when the drive is running, not when powered on.
1.5 External Electromagnetic Interference
Interference sources can cause control circuit malfunctions, leading to shutdowns or damage. Reduce interference by adding RC surge absorbers to relays and contactors, keeping control wiring short and separated from the main circuit. Twist control wires with at least 15 mm spacing and keep them 10 cm away from the main circuit. For long-distance motor connections (>100m), increase wire cross-section and install an output reactor. Ground the inverter properly and avoid mixing with welding or power grounds. Install noise filters at both input and output to reduce harmonic and line noise.
1.6 Installation Environment
Inverters require strict installation conditions. Vibration, moisture, corrosion, and dust can cause mechanical damage, poor contact, or short circuits. Use sealed enclosures and anti-corrosion treatments. Temperature is critical, especially for semiconductors. Avoid direct sunlight and ensure proper ventilation. Regularly check air filters and cooling fans. In cold environments, install heaters to prevent microprocessor failure.
1.7 Power Supply Abnormalities
Power anomalies include phase loss, low voltage, and power outages. Lightning strikes, short circuits, and grid fluctuations are common causes. To protect the inverter, separate its power supply from other devices like motors or induction cookers. For equipment requiring continuous operation, install an automatic uninterruptible power supply (UPS). In cases of phase loss, even though the inverter may continue to run, large currents in the rectifier and capacitor can reduce lifespan and reliability.
1.8 Lightning and Induced Lightning
Lightning-induced surges can damage inverters. Vacuum circuit breakers may generate high-voltage spikes. To prevent this, add varistors at the inverter input and surge absorbers at the vacuum breaker. If a vacuum circuit breaker is present on the transformer side, disconnect the inverter before operating it.
2. Inverter Self-Diagnosis and Prevention Function
Older transistor inverters had issues like frequent tripping and low overload capacity. With IGBT and CPU advancements, modern inverters now feature improved self-diagnosis and fault prevention. Functions like "all-area automatic torque compensation" help overcome issues like insufficient starting torque or reduced output due to environmental factors. Using high-speed microcomputer calculations, the inverter adjusts output voltage to maintain stable torque despite changing conditions.
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