1. Introduction
Ukrainian industrial enterprises face strict requirements for reducing energy consumption and increasing the reliability of equipment. A significant part of the pumping, ventilation and compressor park in the country's factories still uses drives with fixed speed and throttle flow control. This approach is inefficient from the point of view of thermodynamics and mechanics.
EU directives on eco-design and requirements of national legislation on energy efficiency force enterprises to conduct energy audits. Constant operation of the engine at nominal revolutions under variable load leads to excessive wear of mechanical components, high electricity consumption and frequent stops for repairs. Switching to a variable frequency drive (VFD) allows you to eliminate these losses.
In this article, we will look at the technical aspects of retrofitting obsolete drives, provide a methodology for calculating the return on capital investment (CAPEX) and propose a step-by-step plan for the implementation of modern equipment, such as the ABB 990055 series frequency converters (item ex.746927) supplied by UNITEC-D GmbH according to the standards ISO 50001 and EN 61800-3.
2. Evaluation of outdated systems
Before making a decision to replace the equipment, the chief engineer should conduct a complete audit of the current condition of the drive. Legacy solutions based on direct starts (DOL) or legacy thyristor converters often exhibit low power factor and create significant harmonic distortion in the network.
Below are the criteria for evaluating outdated drive systems before modernization:
| Evaluation criterion | Old System (Fixed Speed / Throttle) | Maximum permissible value | Verification method |
|---|---|---|---|
| Engine energy efficiency | Class IE1 or IE2 | Less than IE3 (according to IEC 60034-30) | Power measurement by network quality analyzer |
| Mechanical adjustment | Latches, valves, shutters | Pressure losses > 30% at the throttle | Manometric measurements before and after the armature |
| Vibration level | Above 4.5 mm/s (ISO 10816-3) | Critical zone "C" or "D" | Vibration diagnostics of bearing assemblies |
| Harmonic factor (THD-I) | > 35% (old thyristor circuits) | < 5% (according to IEEE 519) | Oscillography of current and voltage |
| Time to Failure (MTBF) | < 15,000 hours | Frequent failures of bearings and insulation | Analysis of maintenance logs |
The objection "but the old system still works" is often heard from supply or finance departments. However, a full life cycle (LCC) analysis shows that the energy costs for 3 years of operation of a 110 kW motor are 4-5 times the cost of the equipment itself. Operating outdated equipment generates hidden losses due to unplanned downtime.
3. Modern alternatives
A comparison of technologies shows the technical advantage and economic feasibility of switching to modern frequency converters paired with energy-efficient motors.
| Technical parameter | Outdated system (Direct start + Throttle) | Modern system (ABB 990055 + IE3/IE4 engine) |
|---|---|---|
| Method of flow control | Mechanical flow throttling | Changing the engine speed (according to the laws of similarity) |
| System efficiency at 50% load | 40% - 55% | 85% - 92% |
| Starting current | 6 - 8 from the nominal ($I_n$) | 1.0 - 1.2 from the nominal ($I_n$) |
| Power factor ($\cos\varphi$) | 0.70 – 0.82 (falls with frequent loads) | 0.95 – 0.98 (stable in the entire range) |
| Compliance with standards | Does not meet current EN standards | CE, EN 61800-3, EN 60947-4-1, ISO 50001 |
| Equipment protection | Basic thermal relays and fuses | Built-in safety functions (STO SIL3), protection against phase interruption, overvoltage |
The application of Podibius laws for centrifugal mechanisms demonstrates a quadratic dependence of torque and a cubic dependence of power on the speed of rotation ($P \propto n^3$). Reducing the speed of rotation of the pump by only 20% reduces the power consumption by almost 50%.
4. Calculation of return (ROI)
In order to justify investments before the board of directors or investors, we provide a detailed calculation for a typical manufacturing enterprise in Ukraine. The object of modernization is a circulating water supply pumping station with a 132 kW engine (class IE2) operating 7,500 hours per year.
Output data for calculation:
- Rated engine power: $P_n = 132 ext{kW}$
- The average load according to the cycles of the technological process: 70% of the nominal
- Annual fund of working time: $T = 7500 ext{h}$
- The cost of electricity for an industrial enterprise: $C_e = 6.50 ext{UAH/kW}\cdot ext{hour}$ (taking into account transmission and taxes)
- The cost of the modernization kit (ABB frequency converter 990055 (ex.746927), chokes, installation materials, commissioning works): $CAPEX = 450\,000 ext{UAH}$
Energy costs of the old drive (throttling):
When working with a throttle, the consumption remains at the level of approximately 85% of the nominal due to pressure losses: $132 ext{kW} imes 0.85 = 112.2 ext{kW}$.
Annual electricity consumption:
E_old = 112.2 ext{ kW} imes 7500 ext{ h} = 841\,500 ext{ kW}\cdot ext{h} Annual electricity costs:
Cost_old = 841\,500 ext{kW}\cdot ext{h} imes 6.50 ext{UAH} = 5\,469\,750 ext{UAH} Energy consumption of the new drive (VFD ABB 990055):
Due to the cubic dependence of power when the productivity is reduced to 70%, the consumed power is reduced to the level of about 45% of the nominal: $132 ext{ kW} imes 0.45 = 59.4 ext{ kW}$.
Annual electricity consumption:
E_new = 59.4 ext{ kW} imes 7500 ext{ h} = 445\,500 ext{ kW}\cdot ext{h} Annual electricity costs:
Cost_new = 445\,500 ext{kW}\cdot ext{h} imes 6.50 ext{UAH} = 2\,895\,750 ext{UAH} Calculation of savings and payback period:
- Annual electricity savings: $841\,500 - 445\,500 = 396\,000 ext{kW}\cdot ext{h/year}$
- Annual savings in monetary equivalent: $5\,469\,750 - 2\,895\,750 = 2\,574\,000 ext{UAH/year}$
- Reduction of costs for repairs and replacement of worn bearings/seals (load reduction): UAH 120,000/year
- Total annual benefit: $2\,574\,000 + 120\,000 = 2\,694\,000 ext{UAH/year}$
Payback Period:
ROI = (CAPEX / Total Annual Benefit) imes 12 = (450\,000 / 2\,694\,000) imes 12 = 2.0 ext{ months} Even with a more conservative reduction in energy consumption by 25%, the payback period does not exceed 4 months.
5. Step-by-step implementation plan
In order to minimize process stoppages during reconstruction, the engineering service must follow a clear four-stage procedure.
- Planning and audit stage (Weeks 1–2):
- Measuring network parameters and load of the existing engine.
- Designing the connection diagrams of the ABB 990055 frequency converter, taking into account the dimensions and requirements of the EN 60204-1 standard regarding electrical safety.
- Equipment ordering through UNITEC-D GmbH to ensure direct supply of original components.
- Preparation and pre-installation stage (Weeks 3–4):
- Manufacturing and assembly of a new power control cabinet outside the operational production area.
- Laying of cable routes and installation of shielded power cables (according to EMC requirements according to the EN 61800-3 standard).
- Stage of short shutdown and physical replacement (Window 24–48 hours):
- Dismantling of outdated start-up control equipment.
- Installation of cabinet with frequency converter ABB 990055 (ex.746927).
- Connection of power chains and control circuits to the company's PLC.
- Commissioning and handover stage (Week 5):
- Parameterization of protective functions of the converter, setting of the PID controller to maintain pressure or flow.
- Carrying out load tests and signing the commissioning act.
6. Technical difficulties and ways to solve them
Drive modernization is often accompanied by specific engineering challenges that should be addressed at the design stage:
- Electrical Interference and Electromagnetic Compatibility (EMC): The high switching frequency of power transistors (IGBTs) in VFDs creates harmonics and high frequency leakage currents. Solution: use of shielded motor cables, installation of output du/dt filters or sinusoidal filters for cable length over 50 meters.
- Engine heating at low revolutions: When the old engine is running for a long time at a reduced frequency (less than 30 Hz), the built-in cooling fan loses efficiency. Solution: installing independent forced cooling (slit fan) or replacing the motor with an IE3/IE4 class model adapted to work with an inverter.
- Resonant oscillations of the mechanical part: The change in speed can coincide with the natural oscillation frequencies of the shaft line or couplings. Solution: programming of frequency blocking zones (Skip Frequencies) in the parameters of the ABB 990055 converter.
7. An example from practice (Case Study)
A smoke extractor with a 200 kW asynchronous motor was operated at one of the workshops of a cement plant in Ukraine, where the discharge in the furnace was regulated by a damper. The level of vibration on the bearings due to the flow turbulence constantly exceeded 5.8 mm/s, and the motor failed every 9 months due to overheating of the windings.
Upgrading results:
- ABB 990055 frequency converter complete with output filter is installed.
- The shutter is fully open and locked in the 100% position. Discharge regulation is transferred to the change of engine revolutions.
- Measured KPIs before and after:
- Electricity consumption decreased by 38% (from 1,650,000 kWh to 1,023,000 kWh per year).
- The vibration level has decreased to 1.8 mm/s (according to ISO 10816-3 standards for the equipment class).
- MTBF increased from 6,000 hours to over 35,000 hours of continuous operation.
- The actual payback period of the project was 3.2 months.
8. Commissioning and validation
After the installation work is completed, a complex of acceptance and acceptance tests is carried out in accordance with EN 60204-1 and DSTU EN 60034. standards. The procedure includes:
- Checking the insulation resistance of the motor windings with a megohmmeter (voltage 1000 V).
- Control of the correctness of alternating phases and the direction of rotation of the fan or pump.
- Testing of activation of emergency stop circuits (Safe Torque Off — STO).
- Measurement of the level of harmonics in the network and confirmation of compliance with energy efficiency parameters according to ISO 50001.
All data are entered in the passport of the electrical installation, which guarantees legal and technical safety of further operation.
9. Conclusion
The transition from fixed-speed drives to frequency-controlled drives based on modern equipment such as ABB 990055 (ex.746927) is a mandatory step for Ukrainian industrial enterprises seeking to reduce energy consumption and increase the reliability of production lines. The low payback period (2–4 months) makes these investments a priority for CAPEX budgets.
UNITEC-D GmbH provides certified components for the modernization of any industrial systems in accordance with European standards. Check out the range of equipment in our UNITEC-D E-Catalog.
10. Links
- DSTU EN 61800-3:2015 Power electric drive systems regulated by frequency. Part 3. Electromagnetic compatibility requirements and special test methods.
- EN 60204-1 Machine safety. Electrical equipment of machines and mechanisms. Part 1. General requirements.
- IEC 60034-30-1 Electric machines are rotating. Part 30-1. AC motor efficiency classes (IE code).
- ISO 50001:2018 Energy management systems. Requirements and instructions for use.
- Technical documentation of the manufacturer: Manual for installation and operation of frequency converters of the ABB series 990055.
