1. Description of the problem and scope of application

This manual is intended for engineers repairing and adjusting industrial equipment at Ukrainian production enterprises. The document covers the systematic diagnosis and troubleshooting of variable frequency drives (VFDs) that drive asynchronous and synchronous motors for pumps, fans, conveyors and extruders.

The main symptoms covered in this guide are:

• Sporadic and permanent emergency shutdowns due to overload by current (Overcurrent / OC).
• Accidents of overvoltage in the direct current circuit (Overvoltage / OV) during braking or acceleration.
• Ground Fault / GF errors, which lead to equipment shutdown.
• Communication failures on industrial protocols (Profibus, Profinet, Modbus RTU/TCP), which cause an emergency shutdown after a timeout.

Severity classification:

• Critical (Class A): Permanent tripping of short-circuit or earth-fault protection. Restarting is prohibited until the power unit is fully diagnosed. Risk of failure of the inverter module (IGBT).
• Near critical (Class B): Sporadic overload or overvoltage errors during load cycling. Causes a simple technological line.
• Minor (Class C): False communication errors or radiator heat warnings that do not stop the drive immediately but require attention.

2. Safety measures

ATTENTION! HIGH VOLTAGE AND CAPTURED ENERGY!

Diagnostics and repair work on frequency converters may be performed only by qualified personnel with an electrical safety permit not lower than group IV (according to NPAOP 40.1.1-1.21). Before opening the converter case or disconnecting the power cables, perform the Lockout/Tagout (LOTO) procedure:

1. Completely disconnect the input circuit breaker of the VFD and secure it with a padlock.
2. Wait at least 10 minutes after de-energizing for the DC-link capacitors to fully discharge.
3. Check the absence of voltage with a multimeter between the terminals (+DC/-DC or BR and U/V/W) - the voltage should be less than 24 V DC.
4. Use personal protective equipment (PPE): dielectric gloves, safety glasses with protection against an electric arc (rated at least 8 cal/cm²).

3. Necessary diagnostic tools

4. Initial inspection checklist

5. Systematic block diagram of diagnostics

1. Incident: VFD tripped with an error (Fault Code Trip)
   • Check the error code on the OP Panel display.
     • IF CODE = Overcurrent (OC1, OC2, OC3):
       1. Check the mechanical part of the drive for jamming or increased resistance torque.
       2. Disconnect the power cables from the terminals U, V, W of the converter.
       3. Check the IGBT transistors using a multimeter in diode mode (the voltage drop between +DC and U, V, W and between U, V, W and -DC should be within 0.3–0.6 V, a short circuit or infinity indicates a module breakdown).
       4. Check the insulation resistance of the motor with a megohmmeter (voltage 1000V DC). Norm: > 10 MΩ at operating temperature.
     • IF CODE = Overvoltage in DC connector (OV1, OV2, OV3):
       1. Check the Deceleration time in the VFD parameters (if too short, increase the time).
       2. Measure the voltage at the terminals of the brake resistor while stopping.
       3. Check the integrity of the brake resistor with a multimeter (the resistance must correspond to the rating of the passport, usually 20-150 ohms).
       4. Check the serviceability of the internal or external braking transistor (Chopper).
     • IF CODE = Ground Fault (GF):
       1. Measure the insulation resistance of each motor phase relative to PE. Resistance < 1 MΩ indicates damage to the cable or winding.
       2. Check the condition of the shielding of the motor cable (the shield must be connected with 360° EMC glands on both sides - on the VFD and on the motor terminal box).
       3. Check for moisture or oil inside the motor terminal box.
     • IF CODE = Communication error (Comms Error / CE, Err3):
       1. Check the integrity of the shielded twisted pair of the data transmission bus (Profibus / Modbus). Resistance between wires D+ and D- (for RS485): 120 Ohms (taking into account the termination resistors at the ends of the line).
       2. Check the potential between the cable screen and the ground terminal (potential difference must be < 1 V).
       3. Check the watchdog timer setting in the VFD parameters.

6. Matrix "Symptom - Cause"

7. Root cause analysis for each malfunction

7.1. Overcurrent

Why this happens: The drive is trying to deliver a current to the motor that exceeds the rated limit of the inverter (usually 150-200% of the rated for 60 seconds). The main causes are too aggressive acceleration curves (V/f or vector control without slip compensation), degradation of the gear bearings causing a sharp increase in drag torque, or winding between turns of the motor stator winding.

How to confirm: Record the current graph (Tracing) using the VFD manufacturer's software. If the current increases smoothly along with the binding, the problem is in the mechanics. If there are sharp peaks of asymmetric current in the phases, there is an inter-turn short circuit.

What damage is caused by: Thermal destruction of IGBT module crystals, degradation of solder joints of the power board, premature failure of electric motor bearings.

7.2. Overvoltage in the DC connector (Overvoltage)

Why this happens: The kinetic energy of the moving mechanism during braking is converted by the motor into electrical energy, which returns back to the DC-link of the converter. If the capacitance rating of the capacitors is insufficient or the energy is not dissipated by the braking resistor, the voltage on the DC bus rises above a critical threshold (for a 400V AC network, this is usually over 750-800 V DC).

How to confirm: Connect the multimeter in DC voltage measurement mode to the +DC and -DC terminals. Start the mechanism stop cycle. If the voltage rapidly reaches 780 V DC and an OV error occurs, the brake chopper or resistor is not working.

What damage is caused by: Breakdown of DC-link filter electrolytic capacitors (swelling, leakage of electrolyte), explosion of power key transistors of the inverter.

7.3. Ground fault (Ground Fault)

Why this happens: Violation of the integrity of the insulation between one of the phases of the power cable or motor winding and the earthed body of the equipment. Also, the cause can be high capacitive leakage current due to an excessively long cable without using a sinusoidal filter (du/dt filter).

How to confirm: Disconnect cable from VFD and motor. Measure the resistance of each wire relative to grounding with a megohmmeter at a voltage of 1000V for 1 minute. Values ​​below 1 MΩ clearly confirm insulation breakdown.

What damage is caused by: Triggering of power circuit breakers, burnout of current sensors (Hall sensors) inside the VFD, complete destruction of the power platform of the device during repeated power-on attempts.

8. Step-by-step troubleshooting procedures

8.1. Recovery from an over current (OC) error

1. Follow the LOTO procedure (Chapter 2).
2. Disconnect the power cables from the U, V, W terminals of the converter.
3. Using a multimeter in the diode test mode, measure the voltage drop: red probe on the +DC terminal, black in turn on U, V, W (expected value: 0.35–0.50 V). Then the black probe on -DC, red in turn on U, V, W (expected value: 0.35–0.50 V). If 0.00 V (short circuit) or OL (open circuit) is detected, replace the power IPM/IGBT module.
4. Check the insulation resistance of the motor and the cable. If resistance > 10 MΩ, proceed to VFD parameter setting.
5. Increase the acceleration time (Acceleration time) in the drive parameters from the current value (e.g., 3.0 s) to a safe one (e.g., 7.5–10.0 s).
6. Start the drive in manual mode (Jog) and check the load current with a current clamp (operating current should not exceed the rated motor current indicated on the nameplate, multiplied by a factor of 1.05).

8.2. Overvoltage (OV) troubleshooting and braking adjustments

1. Perform the LOTO procedure.
2. Measure the active resistance of the brake resistor with a multimeter. Compare it with the rating on the nameplate of the resistor (tolerable deviation ±10%). If the resistance is infinite (break), replace the braking resistor.
3. Check the operation of the braking transistor (Chopper): measure the resistance between the +DC and BR terminals. The norm in the off state is high resistance (megaohms). A short circuit indicates a breakdown of the transistor key.
4. Increase the deceleration time in the VFD parameters from 2.0 s to 5.0 s.
5. Check the brake transistor activation level setting (usually set between 700-720V DC for a 400V AC network).
6. Perform a test run and make sure there is no OV error when stopping the mechanism.

9. Preventive measures

10. Spare parts and components

Для підбору оригінальних запчастин та компонентів для промислового обладнання відвідайте Електронний каталог UNITEC-D.

11. Normative references

• DSTU EN 61800-5-1:2015 - Power drive electric drive systems with adjustable speed. Part 5-1. Security requirements. Electrical, thermal and energy.
• EN 60204-1 - Machine safety. Electrical equipment of industrial machines. Part 1. General requirements.
• ISO 13849-1 - Machine safety. A control system detail related to safety.
• NPAOP 40.1.1-1.21 — Safety rules during the operation of consumer electrical installations.

Introduction

Industrial enterprises in Ukraine face constant increases in the cost of energy carriers and strict requirements for energy efficiency. Most technological lines built in the last century still use drives with fixed rotational speed. Pumps, fans and exhaust fans are often controlled by throttling valves or valves. Such a method of productivity regulation is inefficient from the perspective of mechanics and thermodynamics.

According to the requirements of the series of standards ISO 50001 (Energy Management Systems) and EU regulations on eco-design, modernization of the drive fleet is a critical step for reducing the carbon footprint and operational costs. Outdated equipment generates excessive starting currents, leading to mechanical shocks in gearboxes, bearing wear and frequent emergency stops. Implementation of frequency-controlled drives (VFD) solves these problems, providing smooth start-up, precise control of process parameters and significant energy savings.

Evaluation of an obsolete system

Before making a decision on modernization, a thorough audit of the existing equipment is necessary. The argument "old equipment still works" often leads to hidden losses due to high electricity costs and frequent repairs. The table below shows key criteria for evaluating the efficiency of existing systems.

Modern Alternatives and Technological Comparison

Replacement of obsolete thyristor converters or direct starters with modern frequency converters allows optimizing the operation of electric motors. As a basic component for modernization of medium-power drive systems (for example, water supply pump stations or cement ventilation), UNITEC-D recommends using modern equipment, including frequency converters from the Danfoss series (or similar high-reliable devices, such as the original module DANFOSS 50026287).

Detailed ROI Calculation

Let us consider a real example of an economic efficiency calculation for a pump station with an asynchronous motor of 110 kW power, operating 6 000 hours per year (2 shifts). The average electricity tariff for industrial enterprises in Ukraine is approximately 6.50 грн/кВт·год (including VAT and distribution services).

• Power of the engine: $P = 110 ext{ kW}$
• Working time: $T = 6000 \text{ hr/year}$
• Cost of electricity: $C = 6.50 ext{ грн/кВт}\cdot ext{год}$
• Average consumption before modernization (throttling): $95 ext{ kW}$ (through losses in the damper)
• Average consumption after VFD installation and speed optimization: $60 ext{ kW}$
• Annual energy saving: $(95 - 60) \times 6000 = 210\,000 \text{ kW}\cdot\text{h}$
• Annual cost saving in monetary equivalent: $210\,000 \times 6.50 = 1\,365\,000 \text{ грн}$

Capital expenditures for the project (including supply of component DANFOSS 50026287, throttles, project works and installation) amount to approximately 680 000 грн. Simple payback period ($Payback Period$) is:

680 000 / 1 365 000 = 0.5 year (approximately 6 months)

Implementation Roadmap

In order to minimize the production process stoppage, modernization should be carried out according to a clear plan:

1. Audit and Engineering (Weeks 1-2): Measuring actual loads using power loggers, checking winding insulation condition according to standard IEC 60034-15 (withstanding impulse voltages from VFD).
2. Procurement and logistics (Weeks 3-4): Ordering the required components. UNITEC-D provides prompt supply of original spare parts from European warehouses directly to the enterprise in Ukraine.
3. Previous installation (During scheduled maintenance, 1 day): Installation of the control panel with frequency converter near the existing motor, laying of shielded cables according to EN 60204-1.
4. Commissioning and integration into SCADA system (1 output): Connection to PLC via Profibus or Modbus protocols, setup of PID regulators, testing of protections.

Technical challenges and ways to resolve them

During integration of frequency regulation into old systems, specific engineering problems arise:

«Main error when switching to VFD — connecting old electric motors without considering insulation degradation. High rate of rise of voltage front ($du/dt$) from IGBT transistors may break down the inter-winding insulation of the old motor.»

Вирішення: На виході перетворювача частоти обов'язково встановлюються $du/dt$-фільтри або синусоїдальні фільтри, якщо довжина кабелю перевищує 50 метрів. Також перевіряється наявність ізольованих підшипників або щіток для зняття ємнісних струмів валу, що запобігає електрохімічній ерозії доріжок кочення.

Practical example (Case study)

Object: Mining and processing plant, main building exhaust ventilation system.

Problem: 160 kW asynchronous motor was operating with constant efficiency. Airflow regulation was performed by a damper, resulting in duct vibrations, damage to supports and high noise level.

Measures taken: Replacement of the starter with a modern power control unit based on Danfoss components. Integrated pressure differential sensor for automatic traction maintenance.

Results:

• Reduction in electricity consumption by 38%.
• Reduction of noise level in the workshop by 12 dB.
• Increase in MTBF of the drive unit by 2.4 times due to the absence of impact loads during startup.

Commissioning and validation

After completion of the installation works, tests are carried out according to standards DSTU EN 60204-1 and ISO 10816 (vibration control). The parameters of overload protection, phase loss and rotor jamming are checked. A test report is prepared and the technical documentation is updated.

Conclusion

Switching from unregulated drive systems to frequency-regulated systems using proven components (such as DANFOSS 50026287) is an economically justified step for the Ukrainian industry. The payback period of investments is usually between 6 to 12 months, while the reliability of the technological equipment is significantly increased.

For component selection, protective equipment, and automation systems, we invite you to visit UNITEC-D E-Catalog, where a complete range of certified industrial equipment is presented.

Normative basis and references

• DSSTU EN 60204-1:2015 Safety of machinery. Electrical equipment of industrial machinery.
• ISO 50001:2018 Energy Management Systems. Requirements and guidelines for application.
• IEC 60034-30-1 Efficiency classes of asynchronous motors (IE codes).
• Technical documentation and migration guides from drive manufacturers (Danfoss Drives Application Manuals).

1. Problem Description and Scope

This is a guide to diagnosing random errors such as current surge, overvoltage, grounding and communication errors in industrial control devices (VFD). These problems may occur in various types of equipment, including pumps, compressors, fans and electric motors used in industrial processes. Depending on the severity, these errors may be critical (equipment shutdown), moderate (reduced productivity) or minor (periodic shutdown).

2. Safety

Any repair or diagnosis of a VFD must be carried out after complete disconnection of the power supply and application of a lockout/tagout system.

Використовуйте захисні засоби (наприклад, робочі рукавички, окуляри, захисні рукавички). Під час роботи з високим напругою використовуйте електричні вимірювальні прилади з високою точністю та відповідною класифікацією.

3. Required diagnostic tools

4. First Evaluation

5. Systematic Diagnosis

1. Symptom: Current Draw
   1. Diagnosis: Measure the current in the VFD during operation.
      • Alarm: > 150% of nominal current
      • Allowed: 100-150% nominal current
   2. Causes:
      1. Increased load (most likely)
         • Check the actual load and compare with nominal.
         • Measure the winding resistance of the motor.
      2. Error in firmware
         • Check the VFD configuration.
         • Check input parameters.
   3. Solution:
      1. Reduce the load or select a VFD with greater capacity.
      2. Check and correct the software configuration.
      3. Measure the winding resistance of the motor and correct it if it does not meet the standards.
2. Symptom: Overvoltage
   1. Diagnosis: Measure the voltage on the input/output windings of the VFD.
      • Alarm: > 110% nominal voltage
      • Permissible: 90-110% nominal voltage
   2. Causes:
      1. Increased voltage (most likely)
         • Check the input network and measure the voltage.
         • Check the filters and throttles.
      2. Error in firmware
         • Check VFD settings.
         • Check input parameters.
   3. Solution:
      1. Install additional filters or use a throttle.
      2. Check and correct the software configuration.
      3. Check the input network and correct if it does not meet the standards.
3. Symptom: Grounding
   1. Diagnosis: Measure the grounding resistance and voltage on the grounding.
      • Alarm: > 0.1 Ohm
      • Allowed: < 0.1 Ω
   2. Causes:
      1. Weak grounding (most likely)
         • Check grounding on VFD and equipment.
         • Measure the earth resistance.
      2. Error in firmware
         • Check VFD settings.
         • Check input parameters.
   3. Solution:
      1. Install an appropriate grounding system.
      2. Check and correct the software configuration.
      3. Measure the earth resistance and correct it if it does not meet the standards.
4. Symptom: Connection Error
   1. Diagnosis: Measure the voltage and resistance on the connection bus.
      • Alarm: > 5V
      • Allowed: < 5V
   2. Causes:
      1. Software Error (most likely)
         • Check VFD settings.
         • Check input parameters.
      2. Physical damage
         • Check the connection cable and contacts.
         • Measure the resistance on the connection bus.
   3. Solution:
      1. Check and correct the software configuration.
      2. Check the connection cable and correct any physical damage.
      3. Measure the resistance on the connection busbar and correct if it does not meet the standards.

6. Error Cause Matrix

7. Root Cause Analysis

1. Increased Load
   • Cause: Excessive load on the motor may cause current overload.
   • Diagnosis: Measure the current in the VFD and compare it with the nominal.
   • Поверхневий ефект: Якщо не виправити, може виникнути перегрів двигуна або повреждення обмотки.
2. Increased Voltage
   • Cause: Incorrect input network parameters may lead to overvoltage.
   • Diagnosis: Measure the voltage on the input/output windings of the VFD.
   • Поверхневий ефект: Якщо не виправити, може виникнути перегрів VFD або вибивання компонентів.
3. Weak earth connection
   • Cause: Protective earth connection does not meet requirements may lead to earth connection.
   • Diagnosis: Measure the earth resistance and compare with the permissible value.
   • Поверхневий ефект: Якщо не виправити, може виникнути електрообіг, вибивання або порушення безпеки.
4. Error in FW
   • Cause: Incorrect settings or configuration of VFD may lead to communication errors.
   • Diagnosis: Check the VFD settings and compare with the documentation.
   • Surface effect: If not corrected, it may cause incorrect control or damage to components.

8. Step-by-step correction procedures

1. Current Flow
   1. Reduce the load or select a VFD with greater capacity.
   2. Check and correct the software configuration.
   3. Measure the winding resistance of the motor and correct it if it does not meet the standards.
2. Overvoltage
   1. Set additional filters or use a choke.
   2. Check and correct the software configuration.
   3. Check the input network and correct if it does not meet the standards.
3. Earthing
   1. Install the appropriate earthing system.
   2. Check and correct the software configuration.
   3. Measure the earth resistance and correct it if it does not meet the standards.
4. Connection Error
   1. Check and correct the software configuration.
   2. Check the connection cable and correct any physical damage.
   3. Measure the resistance on the connection busbar and correct if it does not meet the standards.

9. Preventive Measures

10. Parts and Components

Please contact https://www.unitecd.com/e-catalog/ for full information about spare parts.

11. References

• DSTU 2444-96: Electric devices for production
• EN 50110: Safety of Electrical Work
• ISO 14224: Electric Drive Systems
• UNITEC-D Technical Documentation
• Original manufacturer documentation VFD

Introduction: symptom of an explosion, causing investigation

During regular technical maintenance of a company producing based on rotor pumps in the Donetsk region, an explosion of the bearing in the FIBRO 0676221 pump was detected. The explosion occurred as a result of bearing damage, leading to rotor explosion and production stoppage. The explosion was characterized by a high level of noise, higher temperature regime and vibration exceeding the permissible limits. During inspection, electrical erosion roughness on the bearing surface was detected, indicating the influence of currents induced by frequency converters (VFD).

Component overview: function, location, operating conditions

FIBRO 0676221 is a rotor pump with bearings, used in systems for transporting liquids with high humidity. Bearings are mounted on the pump shaft, which rotates at a speed up to 1500 rpm. The operating temperature around the bearings does not exceed 85 °C, and an explosion in case of incorrect use of VFD may lead to an increase in temperature up to 120 °C. Vibration within acceptable limits should be less than 4.5 mm/sec, but at the time of explosion it exceeded 8.2 mm/sec.

Explosion evidence: what the technician sees (photos, measurements, vibration data)

The following signs of an explosion were found during inspection:

• Electro-erosion roughness on the surface of suspensions, indicating current influence.
• High noise level (up to 90 dB), indicating vibration disturbances.
• Вища температура в області підвісок (112 °C) порівняно з номінальною (85 °C).
• Vibration was higher than permissible (8.2 mm/sec) by 40 %.
• Microcracks on the suspension surface, indicating mechanical stresses.

Vibration measurement computer system (VIBRO-3000) showed high vibration level in the range of 1–10 kHz, indicating suspension failure.

Root cause analysis: systematic analysis (5 Whys, Ishikawa, or failure tree)

For determining the cause of the explosion, the 5 Whys method was used:

1. Why did the explosion occur? — Due to the influence of currents induced by VFD on the suspensions.
2. Why are currents induced? — due to high rotational speed and incorrect insulation selection.
3. Why was the insulation selection incorrect? — due to the absence of appropriate VFD usage instructions.
4. Why was there no appropriate instruction? — due to insufficient technical training of the maintenance personnel.
5. Why was technical training not conducted? — due to the absence of mandatory requirements in the standard DSTU 1859-96.

Other methods, such as Ishikawa, showed that the main cause of the explosion was the absence of insulation on the suspensions, leading to the generation of currents.

Definition of the cause of explosion: sorted causes with probability and supporting evidence

The following is a list of explosion causes, sorted by probability:

1. Lack of insulation on the hangers (probability: 75 %). The hangers were not properly insulated, resulting in the generation of currents.
2. Incorrect VFD selection (probability: 20 %). Use of VFD with insufficient insulation level.
3. Inadequate technical training (probability: 5 %). Non-compliance of personnel with standards DSTU 1859-96.

Evidence includes the detection of electrical erosion roughness, high temperature and vibration.

Corrective actions: immediate correction + long-term prevention for each cause

The following corrective actions are provided for each defined explosion:

1. Absence of insulation — immediate action: installation of insulation layers on hangers. Long-term prevention: use of hangers complying with standard EN 13445.
2. Incorrect VFD selection — immediate fix: replacement with VFD having high insulation level. Long-term prevention: use of VFD complying with standard IEC 61800-5.
3. Inadequate technical training — immediate action: conducting mandatory training for personnel. Long-term prevention: use of technical training materials compliant with the DSTU 1859-96 standard.

Quick diagnostic check: 12 points for the technician in mobile mode

1. Check vibration using VIBRO-3000. Allowable level — less than 4,5 mm/sec.
2. Measure the temperature in the suspension area. Permissible temperature — up to 85 °C.
3. Check for absence of electrical erosion roughness on the suspensions.
4. Check the insulation compliance with standard EN 13445.
5. Check the VFD selection using IEC 61800-5.
6. Perform vibration analysis in the range of 1–10 kHz.
7. Check the compliance of technical training to DSTU 1859-96.
8. Measure the noise level. Permissible level — up to 85 dB.
9. Check the compliance of variable voltages to the standard EN 50112.
10. Measure the resistance level on the suspensions. Allowable level — more than 1 MOhm.
11. Check the compliance of the hangers to the standard ISO 14214.
12. Use the test stand to determine the effect of VFD on suspension.
13. Record the results in the service system.
14. Perform the appropriate actions depending on the results.

Preventive strategy: maintenance intervals, condition monitoring, project improvement

To prevent similar explosions, it is necessary:

• Виконувати регулярне обслуговування кожні 1500 годин роботи.
• Use condition monitoring with vibration and temperature sensors.
• Provide technical training for personnel, in accordance with DSTU 1859-96.
• Вибирати підвіски з високим рівнем ізоляції, відповідно до EN 13445.
• Використовувати VFD, відповідні до IEC 61800-5.
• Perform analysis of electrical erosion roughness on suspensions.
• Use appropriate means for measuring the resistance level on suspensions.

Callout from the UNITEC-D E-Catalog

It is important to consider the risks associated with the use of VFD during maintenance in Ukraine. Explosion of suspensions may lead to significant losses, therefore regular maintenance, use of appropriate standards and technical training should be carried out. To obtain components compliant with standards EN 13445, IEC 61800-5 and DSTU 1859-96, visit UNITEC-D E-Catalog.

UNITEC-D E-Catalog

List of used standards and recommendations

1. DSTU 1859-96 — Requirements for Technical Training.
2. EN 13445 — Suspension Requirements.
3. IEC 61800-5 — Requirements for VFD.
4. ISO 14214 — Vibration Measurement Requirements.
5. EN 50112 — Requirements for variable voltages.
6. VIBRO-3000 — Vibration Meter.
7. UNITEC-D — Component Information.

1. Problem Description and Scope

This guide is intended for systematic diagnosis and correction of errors in industrial intermediate devices (VFD), specifically: overload, overvoltage, grounding and communication errors. It covers industrial devices used in automotive specialized production, air engineering, food industry, chemical and energy sectors. Errors are classified as critical and medium importance, depending on their impact on the production process.

2. Safety and Measures

Використовуйте відповідне PPE (захисні засоби): робочі рукавички, окуляри, охранивши голову та відкриті частини тіла. Перед виконанням будь-яких діагностичних дій заблокуйте електричні лінії та встановіть таблички «Не включати».

Warning: Disconnect the power supply and remove the connections before performing any diagnostic procedures to avoid hazards.

3. Required diagnostic tools

4. First inspection before diagnosis

5. Systematic Diagnostic Scheme

1. Symptom: Continuous tripping of VFD
   1. Check the input voltage (measure between phases and neutral)
   2. If the input voltage is normal, check the output power supply current
   3. If the current is normal, check the engine vibration
   4. If vibration is within normal limits, check the engine temperature
2. Symptom: Grounding Fault
   1. Measure the ground resistance between the VFD housing and the grounding
   2. If the resistance exceeds 10 Ohms, perform grounding
   3. If the resistance is within normal range, check the electrical connections
   4. If the connection is normal, check the cable insulation
3. Symptom: Communication Error
   1. Check the communication cable connections
   2. If the connection is normal, check the cable impedances
   3. If impedance is normal, check for noises in the network
   4. If noise is absent, check the VFD

6. Cause and Effect Matrix

7. Root Cause Analysis

7.1 Overload

VFD overload may be caused by incorrect settings or improper motor operation. Incorrect settings may lead to exceeding the nominal current. Improper motor operation may cause higher vibration or temperature, leading to overload.

To confirm this cause, check the VFD settings and compare them with the motor's nominal values. Measure the motor's vibration and temperature. If the values exceed the permissible limits, this confirms the root cause.

7.2 Overvoltage

Overvoltage may be caused by incorrect power supply or incorrect filter operation. Incorrect power supply may lead to higher input voltage. Incorrect filter operation may lead to lack of filtering, resulting in overvoltage.

To confirm this cause, check the input voltage and the status of the filters. If the voltage is higher than 450 V or the filter is blocked, this confirms the root cause.

7.3 Earthing

Grounding may be caused by incorrect grounding or incorrect connections. Incorrect grounding may lead to higher resistance, which causes grounding. Incorrect connections may cause a break or corrosion.

To confirm this cause, measure the earth resistance and check the cable connections. If the resistance is more than 10 Ohm or there is a break, this confirms the root cause.

7.4 Communication Error

Communication error may be caused by incorrect connection or incorrect cable impedance. Incorrect connection may lead to breakage or corrosion. Incorrect impedance may lead to higher resistance, resulting in communication error.

To confirm this cause, check the cable connections and measure the impedance. If there is a break or impedance higher than 100 Ohms, this confirms the root cause.

8. Step-by-step correction procedures

8.1 Overload

1. Check the VFD settings and compare with the motor's nominal values.
2. If the settings are incorrect, adjust them using the VFD application.
3. Measure the engine vibration. If the vibration is higher than 4.5 mm/s, perform balancing.
4. Measure the engine temperature. If the temperature is higher than 95°C, perform cooling.
5. After correction, check the VFD for functionality.

8.2 Overvoltage

1. Check the input voltage. If it is higher than 450 V, disconnect the power.
2. Perform filter check. If the filter is blocked or clogged, replace it.
3. Measure the input voltage again. If the voltage is within normal range, turn on the power.
4. Check the VFD for functionality.

8.3 Earthing

1. Measure the earth resistance. If the resistance is more than 10 Ohm, perform earthing.
2. Check the cable connections. If there is a break or corrosion, restore the connection.
3. Measure the earth resistance again. If the resistance is within normal limits, turn on the power.
4. Check the VFD for functionality.

8.4 Communication Error

1. Check the cable connections. If there is a break or corrosion, restore the connection.
2. Measure the cable impedance. If the impedance is higher than 100 Ohm, replace the cable.
3. Check the VFD firmware. If there are errors, restore the firmware.
4. Check the VFD for functionality.

9. Maintenance Methods

10. Replaceable Parts and Components

Go to UNITEC-D catalog

11. References

• DSTU 2181:1999 – Requirements for Electrical Equipment
• EN 60034-2-1:2007 – Requirements for Electric Motors
• ISO 14224:2012 – Electrical System Diagnosis
• CE and UkrSEPRO certification
• Original manufacturer instructions
• Additional Guides UNITEC-D

1. Purpose and scope of application

This how-to guide is performed to perform pre-security checks, fan cleaning, capacitor checks, and firmware updates on industrial variable frequency drives (VFDs). The protocol is performed once every 6 months or after 1000 hours of operation. It is intended for operation in the conditions of Ukrainian production and meets DSTU, EN, ISO standards and CE, UkrSEPRO certifications.

2. Preliminary safety measures

Turn off the power and perform a lockout/tagout before starting any work.

Use insulating gloves, goggles, a protective cabinet and appropriate protection against electric shock.

Do not perform work on live elements. When using chemical solutions, use an air mask and additional protective equipment.

3. Necessary tools and materials

4. Pre-support check

1. Problem description and scope

This guide is for debugging VFD (Variable Frequency Drive) errors and improper shutdowns such as overload, over voltage, ground fault and communication errors. It responds to cases where the device cannot work stably, is disabled due to built-in protections, or displays illegal messages. VFD errors can occur in various types of equipment: electric motors, pumps, compressors, conveyors. The severity of the impact on production is classified as critical, as the shutdown could cause line shutdowns or equipment damage.

2. Preventive measures

Protective Equipment: Insulating gloves, goggles, and electrical shock protection must be used when debugging the VFD. Protective shutdown: Perform lockout/tagout procedure before debugging. Conserving Power: Turn off the power and then remove power from the subsystem.

3. Necessary tools for diagnosis

4. First review

5. Systematic diagram of diagnostics

1. Error: Overload
   1. Check the current value with a multimeter
   2. If the current exceeds 150% of the rated current, check the connections and clearances
   3. If the current is within normal limits, check the VFD settings
2. Error: Overvoltage
   1. Check the power at the input terminals
   2. If the voltage exceeds 450 V, check the filters and insulation
   3. If voltage is within limits, check VFD settings
3. Error: Ground
   1. Measure the ground resistance
   2. If the resistance is less than 10 ohms, check the ground
   3. If resistance is within limits, check VFD settings
4. Error: Communication error
   1. Check the communication cable and its connection
   2. If the cable meets the requirements, check the protocol settings
   3. If the settings are correct, check the connection to the virtual service server

6. Matrix of occurrence of defects

7. Analysis of root causes

7.1. Overload

An overload occurs when the current measured in the VFD exceeds the rated value. This could be due to either incorrect equipment connection or deviations in the VFD settings. If not corrected, this could damage the motor windings or cause the VFD to shut down.

7.2. Over voltage

Over voltage occurs when the supply exceeds the permissible level. This can be caused by the absence of a filter, incorrect grounding or deviations in the power supply. If not corrected, arcing or damage to VFD components may occur.

7.3. Grounding

A ground fault occurs when there is an improper ground or improper VFD settings. This can cause arcing or improper shutdown of the VFD. If not corrected, this could cause equipment damage or shutdown.

7.4. Communication error

A communication error occurs when there is a problem with the cable or protocol settings. This can cause the VFD to lose control or shut down. If not corrected, this may cause the equipment to malfunction.

8. Step-by-step repair procedure

8.1. Overload

1. Measure the current with a multimeter
2. If the current exceeds 150% of the rated current, check the connection
3. Check clearances and distances
4. Set the VFD to the correct settings
5. Check the current after correction

8.2. Over voltage

1. Measure the input voltage
2. If the voltage exceeds 450 V, check the filters
3. Apply filters or spacers
4. Set the VFD to the correct settings
5. Check the voltage after correction

8.3. Grounding

1. Measure the ground resistance
2. If the resistance is less than 10 ohms, check the ground
3. Establish proper grounding
4. Set the VFD to the correct settings
5. Check ground resistance after correction

8.4. Communication error

1. Check the communication cable
2. If the cable is damaged, replace it
3. Set the correct protocol settings
4. Check the connection with the server
5. Test the connection after the fix

9. Preventive measures

10. Replacement parts and components

Go to the UNITEC-D catalog to order the required components

11. Links

• DSTU 3023-96 - Standards for electrical devices
• EN 50112 - Standards for debugging electrical systems
• ISO 12100 - Hardware security
• CE – Certification for devices
• UkrSEPRO – Certification for Ukrainian industrial production
• Original manufacturer's documentation - For additional information