Introduction

Ukrainian industry faces a critical need to reduce energy consumption and increase the efficiency of production processes. A significant part of the equipment at domestic enterprises still operates drives with unregulated speed. Throttling with valves, guiding devices or the use of slip clutches leads to colossal energy losses. European energy efficiency regulations, in particular the EU regulations on ecodesign (Ecodesign Directive) and the standards of the ISO 50001 series, stimulate the transition to systems with adjustable rotation frequency.

Modernization of outdated systems not only reduces electricity costs, but also extends the life of the mechanical part of the equipment. UNITEC-D GmbH engineers in their practice regularly face the position: "old equipment still works, why invest?". Below we provide a technical and economic calculation and a detailed transition plan that proves the fallacy of such an approach.

Assessment of legacy systems

Before making a decision to dismantle the existing equipment, the chief engineer of the enterprise is obliged to conduct an audit. The main criteria for evaluating obsolete drives are given in the table below.

Technology Comparison: Legacy System vs. VFD

A classic throttle valve drive consumes constant electrical power regardless of the demand of the working environment. A frequency converter (VFD) changes the speed of rotation of the motor according to the cubic dependence of power on speed ($P \\sim n^3$). This means that reducing pump or fan speed by 20% cuts energy consumption almost in half.

ROI calculation for an industrial facility in Ukraine

Let's consider a real example of modernization of a pumping station at a cement plant. Parameters of the existing installation:

• Engine power: $P = 160$ kW
• Average load during the year: 75%
• Operating hours: 7,500 hours per year (continuous cycle)
• The cost of electricity for industry: UAH 6.00/kWh (including VAT)
• Consumption of the old system (taking into account losses at the throttle): 140 kWh
• Consumption of new system with VFD: 85 kWh

Calculation of annual energy savings:

$$\\Delta E = (140 \ ext{ kW} - 85 \ ext{ kW}) \ imes 7500 \ ext{ h} = 412 500 \ ext{ kWh/year}$$

Financial savings for the year:

$$\ ext{Economy} = 412,500 \ ext{ kWh} \ imes 6.00 \ ext{ UAH/kWh} = 2,475,000 \ ext{ UAH}$$

Taking into account the investment costs for the equipment (160 kW VFD, chokes, cable products, installation work and an Allen Bradley 2711P-K6M20D operator panel for control and monitoring), the total project budget is approximately UAH 1,200,000.

Payback period ($PP$):

$$PP = \frac{1,200,000 \ ext{ UAH}}{2,475,000 \ ext{ UAH/year}} \\approx 0.48 \ ext{ year (about 5.8 months)}$$

Even taking into account the costs of stopping production (conditionally UAH 200,000 for 24 hours of downtime), full payback is achieved in less than 7 months.

Phased implementation plan

In order to minimize the impact on the production process, modernization is carried out according to a clearly regulated schedule:

1. Stage 1: Design and audit (Weeks 1-2). Measurement of real loads, analysis of network harmonics according to the requirements of DSTU EN 61000-3-4, selection of frequency converter ratings and related equipment.
2. Phase 2: Supply of components (Weeks 3-6). Procurement of power cables, electromagnetic compatibility (EMC) filters, inverters and interface panels via UNITEC-D E-Catalog.
3. Stage 3: Pre-installation (Weeks 7-8). Assembling the new control cabinet in the off-season or during a short technological window. Allen Bradley 2711P-K6M20D operator panel integration for visualization of process parameters.
4. Stage 4: Connection and commissioning (Technological stop, 24-36 hours). Dismantling of old starters, connection of VFD power circuits, adjustment of PID controllers according to standards ISO 21749.
5. Stage 5: Validation and Commissioning (Week 9). Load testing, checking the level of harmonics, training shop staff.
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Technical challenges and ways to solve them

When integrating VFDs into old lines, specific engineering problems arise that require a professional approach:

• Surge at the motor terminals: Long cables (more than 50 m) between the inverter and the motor cause reflected waves and high voltage peaks that destroy the old insulation. Solution: Installation of output du/dt filters or sine filters according to DSTU EN 60034-17.
• Electromagnetic interference (EMI): High-frequency switching of IGBT transistors creates interference for sensors and ASKTP systems. Solution: Use of shielded cables with grounding ends according to ISO 61800-5-1. standards
• Resonant frequencies of fans and pumps: Operation at certain speeds can cause mechanical resonance of the structure. Solution: Programming of frequency blocking zones (skip frequencies) in the converter parameters.

Example from practice: Modernization of smoke extractor in metallurgy

At one of the enterprises of the mining and metallurgical complex of Ukraine, a smoke extractor with a capacity of 250 kW with a guide device was operated. The parameters before and after the upgrade are shown below:

Indicator	Before modernization (Guide apparatus)	After upgrade (VFD + Allen Bradley 2711P-K6M20D)
Specific energy consumption	195 kWh/ton of products	128 kWh/ton of products
Mean Time Between Failure (MTBF)	8,500 hours (repair of bearings, replacement of blades)	> 35,000 hours
Accuracy of rarefaction support	± 45 Pa	± 5 Pa

Commissioning and acceptance criteria

After completion of the installation works, a comprehensive test is carried out in accordance with the technical regulations:

1. Insulation resistance test of the motor with a megohmmeter (not less than 20 MΩ at 1000 V).
2. Testing of the operation of emergency protections (emergency stop, overload, interruption of the pressure sensor).
3. Measurement of current harmonic distortions ($THDi$) in the transformer substation network (must comply with IEEE 519 standards).
4. Functionality testing of a Human Machine Interface (HMI) such as the Allen Bradley 2711P-K6M20D for correct display of emergency alarms and pressure/flow trends.

Conclusion

The transition from constant speed drives to frequency regulation is an economically justified step for Ukrainian industry. A short payback period (less than a year) combined with a reduction in the load on the mechanical part makes this investment critical for the company's competitiveness. UNITEC-D GmbH engineers are ready to provide full technical support, select frequency converters, sensors and operator panels such as the Allen Bradley 2711P-K6M20D. Get acquainted with the assortment of components in our catalog: UNITEC-D E-Catalog.

Normative References

• DSTU EN 60034-1:2016 Rotating electrical machines. Nominal data and operating characteristics.
• DSTU EN 61800-5-1:2015 Systems of Adjustable Speed Power Drives. Safety Requirements.
• ISO 50001:2018 Energy Management Systems. Requirements and guidelines for application.
• IEEE 519-2014 Recommended Practice and Requirements for Harmonic Control in Electric Power Systems.

1. Introduction

Industrial enterprises in Ukraine face an urgent need to reduce production energy consumption. The increase in electricity tariffs and strict requirements of European energy efficiency standards make the operation of outdated equipment economically unviable. Traditional systems with constant speed drives, controlled by throttling using valves or dampers, lose up to 40% of energy on mechanical resistance.

According to the requirements of EU regulations on eco-design and standard ISO 50001, system audit of electric drives is a mandatory element of energy efficiency management. Modernization of such systems by implementing frequency converters (VFD) allows precisely matching the equipment performance with real technological needs. In this technical guide, we consider the engineering aspects of transition to frequency regulation, investment payback calculation and phased implementation plan using the example of modernization of pumping, ventilation and conveyor units with components from UNITEC-D GmbH.

2. Evaluation of obsolete systems

The main psychological barrier for engineers and main energy personnel sounds like: "The old system works and is maintained by the own workshop." However, such an approach ignores the hidden costs of electricity, frequent mechanical part repairs due to hydraulic shocks and equipment downtime.

Before making a decision on disassembly or modernization, a comprehensive audit should be conducted according to the following criteria:

3. Modern Alternatives and Technological Comparison

Switching from throttling to frequency regulation fundamentally changes the operating characteristics of the unit according to the similarity laws of centrifugal machines. A 20% reduction in the engine speed reduces the consumed power almost by half (cubic dependency for resistance moments of fan type).

For complex mechanical transformations and torque transmission in modern modernization projects, high-precision components are used. For example, the use of advanced units, such as the precision mechanical component FIBRO 2192.50.04.012, allows ensuring tight tolerances in positioning and force transmission without play, which is critically important when operating in pulse modes at variable speeds.

4. Detailed ROI Calculation

Let us consider the economic efficiency of modernizing the technical water pumping station of the metallurgical complex. Conditions of the task:

• Power of the installed asynchronous motor: N = 75 kW.
• Mode of operation: 6 000 hours per year (3 shifts, continuous cycle).
• Average electricity cost for an industrial enterprise: 6.50 грн/kW·h (including VAT and distribution).
• Average load on the shaft during throttling: 85% of nominal (with losses on the throttle being approximately 30%).

1. Calculation of energy costs before modernization:

Power consumption: $75 \text{ kW} \times 0,85 = 63,75 \text{ kW}$.Annual consumption: $63,75 \text{ kW} \times 6000 \text{ h} = 382 500 \text{ kW·h}$.Annual costs: $382 500 \times 6,50 = 2 486 250 \text{ грн}$.

2. Calculation of consumption after installation of VFD and optimization:

Thanks to the absence of throttling losses and operation according to similarity laws, the average energy saving is 32%.

New annual consumption: $382 500 \times (1 - 0,32) = 260 100 \text{ кВт·год}$.New annual costs: $260 100 \times 6,50 = 1 690 650 \text{ грн}$.

3. Economy and payback:

Annual cost saving: $2 486 250 - 1 690 650 = \mathbf{795 600 \text{ грн}}.

Capital expenditures for the "turnkey" project (including 75 kW frequency converter, chokes, installation works, commissioning and supply of precision parts through UNITEC-D): 950 000 грн.

Payback period ($T_{pay}$):

$$T_{pay} = \frac{950 000}{795 600} \\approx 1,19 \text{ year (approximately 14 months)}$$

Taking into account the reduction in costs for bearing unit repairs and valve replacement (saving about 120 000 грн per year), the real payback period is reduced to 11 months.

5. Implementation Roadmap

In order to minimize the production process stoppage, modernization is carried out according to a phased schedule:

1. Stage 1: Design and Audit (Weeks 1–2). Conducting measurements of network parameters, selection of VFD ratings, development of control panel layout drawings in accordance with PUE and DSTU EN 60204-1.
2. Stage 2: Equipment Supply (Weeks 3–5). Contracting through UNITEC-D GmbH for the necessary electronic components and mechanical units (including specialized parts such as FIBRO 2192.50.04.012).
3. Stage 3: Preliminary assembly (Weeks 6–7). Assembly of the VFD control cabinet in the assembly shop without interrupting main production. Conducting no-load tests.
4. Step 4: Short-term shutdown and replacement (Window 48 hours). Disassembly of the old motor control equipment, connection of VFD, integration into the existing SCADA system via Profibus/Modbus protocols.
5. Stage 5: Commissioning and Validation (Week 8). Setting up acceleration/deceleration parameters, dry run protection and overload protection. Preparation of commissioning certificate.

6. Technical Problems and Ways of Their Solution

Modernization of high-voltage and low-voltage drives often involves specific engineering risks:

• Harmonic impact on the power supply network: Operation of VFD creates higher harmonic distortions (THDi up to 35–40%). Solution: Mandatory installation of 6- or 12-pulse rectifiers or active harmonic filters (according to the IEEE 519 standard).
• Insulation breakdown of motor windings: Steep front edges of voltage pulses at the inverter output ($dU/dt$) cause reflected waves in cables longer than 20 meters. Solution: Use of motor chokes ($du/dt$ filters) and sinusoidal filters.
• Resonant vibrations: At certain rotational frequencies, there may be a coincidence of frequency with the natural oscillations of the mechanical system. Solution: Programming forbidden speed zones (skip frequencies) in the frequency converter.

7. Practical Example: Before and After

Modernization of the exhaust fan drive for the raw mill was carried out at a cement plant in the Dnipro region (asynchronous motor 160 kW, voltage 380 V).

Condition before modernization: Vacuum regulation in the mill chamber was performed by a slide valve. Bearing vibration exceeded standard values by 45%. Electricity consumption amounted to 910 000 kW·h per year. Frequent stoppages due to burning out of magnetic contactor contacts.

Post-modernization status: A vector-controlled frequency converter was installed and a mechanical part revision was carried out using original UNITEC-D components. Vibration level was stabilized within the norm (2,1 mm/s). Electricity consumption decreased to 630 000 kWh per year. The savings in the first year amounted to 280 000 kWh (1 820 000 грн).

8. Commissioning and validation

After completion of the installation works, a comprehensive test is conducted in accordance with the state standards of Ukraine and EU norms:

1. Insulation resistance testing of power cables and motor windings with a 1000 V megohmmeter (value not less than 20 MOhm).
2. Testing of overload protection, short circuit protection and phase loss protection.
3. Measurement of electromagnetic compatibility (EMC) and checking for absence of malfunctions in adjacent measuring instruments.
4. Signing of the acceptance test protocol and delivery of the execution documentation to the customer.

9. Conclusion

Switching from constant speed drives to frequency regulation is not just a replacement of equipment, but a fundamental engineering step towards reducing product cost. Investments in modernization are generally recovered within 12–14 months due to significant electricity savings and increased reliability. UNITEC-D GmbH is ready to provide full technical support, equipment selection and supply of original spare parts for your company. Please check our range in UNITEC-D E-Catalog for selection of industrial automation components and drive technology.

10. References

• ISO 50001:2018. Energy Management Systems. Requirements and guidelines for use.
• DSTU EN 60204-1:2015. Machinery Safety. Machinery Electrical Equipment. Part 1. General Requirements.
• IEC 60034-30-1:2014. Обертові електричні машини. Частина 30-1. Класи ефективності лінії живлення асинхронних двигунів (код IE).
• IEEE Std 519-2014. IEEE Recommended Practice and Requirements for Harmonic Control in Electric Power Systems.