An Effective Solution for Forced and Induced Draft Fans: EF High-Voltage Electric Motors in Action

Project / Customer

Project: An effective solution for boiler draft fans: development, manufacturing and supply of high-voltage electric motors of the proprietary "EF" brand for new CHP units.
Customer: A major Russian power generation company
Equipment: Boiler draft fan systems (induced draft fans and forced draft fans)
Product: Asynchronous high-voltage electric motors of the proprietary "EF" brand
Manufacturing geography: PRC (own certified production site)

Introduction

As part of the construction of new CHP units, the customer needed to select electric motors for boiler draft fans of types VDN-31.5K-0.95, DN-32x2-0.62K-0.97 and DRG-32-100.

The engineers of "Energofront" faced a complex task: to develop and supply a batch of asynchronous electric motors with a capacity of 1250 kW, 2000 kW and 1600 kW within a tight schedule, ensuring their reliable direct-on-line starting and operation in extreme climatic conditions.

Key challenges at the start:

• Heterogeneity of equipment: 3 non-standard machine sizes with different aerodynamic and torque curves.
• Strict direct-on-line starting requirements: 2 consecutive starts from a cold state, 1 start from a hot state.
• Extreme climatic design: ambient temperature range from -60°C to +40°C.
• Tight delivery schedule.

Task and technical requirements

To develop, manufacture and supply a batch of asynchronous electric motors with the following parameters:

Key engineering task: to calculate and design electric motors with specified starting characteristics, taking into account direct-on-line starting and operation in low ambient temperature conditions, ensuring the start-up of draft fans within the required time to avoid overheating.

Individual engineering solutions

1. Aerodynamic analysis

The "Energofront" engineers requested the characteristics of the draft fans and performed a recalculation of the reduced aerodynamic curves (dependence of the mechanism resistance on performance). Based on this data, the motor characteristics (electromagnetic torque shape) were adjusted, which made it possible to eliminate "dips" when reaching the operating mode.

2. Engineering and design adaptation

Motors were designed with the following technical features:

• Aluminum rotor – to ensure the required starting properties for the 1250 kW and 2000 kW electric motors.
• Reinforced Class F insulation with a heating margin up to Class H – for reliability during operation in UHL3 conditions, -60°C…+40°C.
• IP54 enclosure protection – protection against dust and moisture, inevitable in the draft fan installation area.

Accounting for the moments of inertia of the mechanism rotor:

• For the 1250 kW electric motor – J = 3900 kg/m²
• For the 2000 kW electric motor – J = 8000 kg/m²
• For the 1600 kW electric motor – J = 3500 kg/m²

3. Production at the site in the PRC

Production was deployed at a certified site in China. Why this became an advantage:

• Optimized procurement of electrical steel and copper (cost reduction without loss of quality).
• Availability of a test bench with a capacity of up to 5 MW – allowed to carry out 4-hour tests under nominal load.

Testing and quality control

All electric motors passed the full cycle of factory tests according to the GOST methodology (IEC analogue):

1. Insulation resistance measurement (with a 2500 V megohmmeter).
2. High-voltage test (Utest = 2Unom + 1000 V) for 1 minute.
3. Removal of load characteristics (operation under nominal load with measurements of current, active power, temperatures of windings and bearings).
4. Vibro-acoustic diagnostics – the vibration level did not exceed 2.8 mm/s (Class A according to GOST ISO 10816-3).

Test results: Actual deviations in no-load current and efficiency did not exceed the passport values (+0.5%). The motors successfully operated for 2 hours in a forced mode (10% overload). Locked rotor tests: 5.54 In, 1.62 Tn.

Implementation at the customer's site

The supply of electric motors with a complete set of accompanying documentation (Drawings, operation manual, Passports, test protocols, quality certificates, installation instructions) was completed within the strictly agreed timeframe.

Summary of achieved results

Conclusion

The project for the supply of high-voltage "EF" electric motors confirmed the ability of the "Energofront" team to solve complex engineering tasks at the intersection of aerodynamics, electromagnetic design and adaptation to extreme climatic conditions.

Successful direct-on-line starting of heterogeneous draft fans, ensuring high efficiency and significant savings in the customer's budget (reduction of the contract cost by 48%) demonstrate the company's systematic approach:

• In-depth technical expertise — aerodynamic analysis and accurate calculation of the electromagnetic torque to eliminate "dips" during starting.
• Adaptation to extreme conditions — the use of reinforced insulation and special design solutions for operation at -60°C.
• Production optimization — the use of a certified site in the PRC to reduce the cost without loss of quality.
• Multi-level quality control — a full cycle of tests according to GOST, including 4-hour loads and vibro-acoustic diagnostics.

The implemented project ensured the reliable start-up of new CHP units and contributed to increasing the energy efficiency of Russian power generation.