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Energy & Power Mining Energy Systems

High-Integrity Regenerative Hoist Control System for Deep Shaft Mining

Update: 2026-01-17

Problem Definition

Industry Challenges

  • 01 High energy consumption due to continuous heavy lifting cycles in deep shaft operations
  • 02 Mechanical stress and fatigue on ropes and sheaves caused by abrupt torque application
  • 03 Strict regulatory requirements for personnel safety (SIL2/SIL3) in vertical transport
  • 04 Heat generation in underground environments from traditional dynamic braking resistors

Specific Pain Points

  • Inconsistent cage leveling leading to loading/unloading delays and safety hazards
  • Excessive wear on mechanical brake pads due to use for deceleration rather than just holding
  • Grid instability caused by high harmonic distortion during heavy startup loads
  • Lack of real-time diagnostic data for rope slip and drum overspeed conditions

Current State Analysis

"Existing systems often rely on outdated DC drives or non-regenerative AC drives, wasting potential energy as heat. Safety relies heavily on mechanical redundancy without integrated electronic speed supervision. Control loops lack the bandwidth to effectively dampen rope oscillations during acceleration."

Performance Impact

Speed Regulation
0.01% steady state with closed-loop vector control
Energy Regeneration
20-35% net energy recovery (cycle dependent)
Positioning Accuracy
±10 mm at shaft bottom (depth >1000m)
Torque Response Time
< 5 ms
Safety Integrity Level
SIL 3 (IEC 61508) for Overspeed and Overtravel protection
Braking Torque 250% (Mechanical Emergency Rating)
Drive Topology Medium Voltage 3-Level NPC Inverter with Active Front End
Overload Capacity 150% for 60 seconds / 200% for 3 seconds
Harmonic Distortion (Thdi) < 5% at PCC
Engineering Verification

This solution has been validated by Atlamech Engineering based on the following standards:

View Details

Technical Scope

  • Retrofit of existing hoist drive with Medium Voltage (MV) 4-Quadrant VFD with Active Front End (AFE)
  • Implementation of a dedicated Safety PLC (SIL3) independent of the process controller
  • Installation of dual-redundant encoder systems (Absolute + Incremental) for precise position and speed feedback
  • Integration of hydraulic brake control units with Safe Brake Control (SBC) and Safe Brake Test (SBT) functionality

Compliance Standards

IEC 61508 (Functional Safety of Electrical/Electronic/Programmable Electronic Safety-related Systems)
IEC 62061 (Safety of Machinery)
IEEE 519 (Harmonic Control in Electric Power Systems)
Local Mining Regulations (e.g., MSHA 30 CFR, MHSA)

Implementation Strategy

Phase 1 (Weeks 1-3): Site survey, load profile analysis, and safety integrity level (SIL) assessment. Phase 2 (Weeks 4-12): System design, procurement of MV Drives and Safety PLCs, and FAT (Factory Acceptance Testing). Phase 3 (Weeks 13-15): Installation during scheduled shutdown, focusing on encoder retrofit and drive replacement. Phase 4 (Weeks 16-17): SAT (Site Acceptance Testing), load testing with test weights, and operator training.
Key Deliverables
SIL Verification and Validation (V&V) Report
Electrical Single Line Diagrams (SLD) and Control Schematics
Harmonic Analysis Report (IEEE 519 compliance)
Commissioning Plan including Drop Testing and Emergency Stop validation

Consultation Notes

Safety Architecture & Braking Strategy

For SIL3 compliance, the safety functions must be hardware-independent from the operational drive control. The Safety PLC must directly monitor the redundant encoders and control the Safe Torque Off (STO) and Safe Brake Control (SBC) relays. The VFD software is considered 'Black Channel' and cannot be the sole layer of protection.

Regenerative Energy Management

In deep shaft hoisting, significant potential energy is generated during the lowering of heavy loads (or empty skips in unbalanced systems). An Active Front End (AFE) is mandatory to return this energy to the grid with unity power factor, eliminating the need for massive braking resistor banks and reducing tunnel cooling loads.

Rope Dynamics & Jerk Control

To prevent rope oscillation and mechanical fatigue, the speed reference must utilize an S-Curve ramp (limiting jerk/derivative of acceleration). The drive tuning must account for the variable resonant frequency of the rope as the length changes during the hoist cycle.

Infrastructure Taxonomy

Medium Voltage Regenerative VFDs (Active Front End)
SIL3 Certified Safety PLCs
Heavy-Duty Absolute Encoders (SSi/Profisafe)
Hydraulic Disc Brake Calipers with Sintered Linings
Power Quality Filters (LCL Filters)
Typical Application Patterns: Koepe (Friction) Hoist Modernization Double Drum Hoist Retrofit Blair Multi-Rope Hoist Control Upgrade

Knowledge Areas

Mining Power Systems & Energy Infrastructure

Engineering Relation Summary

Technical Components

Medium Voltage 4-Quadrant VFD, Dual-redundant Encoder System, Safety PLC (SIL3)

Engineering Constraints

Overload Capacity (150% for 60s)

Core Optimization Logic

Closed-loop Vector Control Algorithm

Implementation Evidence Summary

Project Brief

Deep Shaft Regenerative Hoist Control Implementation

System Scale
Dual-drum friction hoist driven by a 4.5 MW Medium Voltage motor; vertical lift of 1,200 meters; payload capacity of 35 metric tonnes.
Operating Conditions
Remote site with weak utility grid connection; ambient control room temperatures reaching 45°C; continuous 24/7 extraction cycles.
Implementation Constraints
Grid code compliance mandated THDi <5% at the Point of Common Coupling (PCC). Safety protocols required IEC 61508 SIL 3 certification for both overspeed and overtravel functions independent of the primary PLC.

Technical Knowledge Cluster

Mining Power Systems & Energy Infrastructure

Targeting B2B engineering and procurement intent, this cluster addresses the transition to electrified and decarbonized mining operations. Key themes include hybrid microgrids, renewable energy integration, and load management strategies designed to optimize cost per kWh and ensure high-availability power for extraction and processing equipment.

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