Complete design and documentation of an industrial electrical panel for three-phase motor control using star-delta starting method, featuring 3D CAD modeling, electrical schematics, and component integration.

Project Overview

This project presents the complete design of an industrial electrical panel for controlling a 12 HP three-phase induction motor using the star-delta (Y-Δ) starting method. The star-delta configuration reduces inrush current during motor startup by initially connecting the motor windings in star configuration, then switching to delta configuration for normal operation.

The design encompasses electrical calculations, circuit schematics, component selection, 3D CAD modeling, and complete technical documentation following industrial standards.

Star-Delta Starting Method

Why Star-Delta?

When a three-phase induction motor starts directly (DOL - Direct On Line), it draws 6-8 times its rated current, causing:

• Voltage dips in the electrical network
• Mechanical stress on the motor and connected equipment
• High peak demand charges from utilities

The star-delta starter reduces starting current to approximately 1/3 of DOL starting current by:

1. Star Connection (Y): Motor windings receive $\frac{V_L}{\sqrt{3}}$ voltage, reducing current
2. Time Delay: Allows motor to accelerate (typically 5-15 seconds)
3. Delta Connection (Δ): Full voltage applied for normal operation

Electrical Calculations

For a 12 HP motor at 120V line-to-neutral:

Control System Architecture

Contactor Arrangement

The system uses three ABB A40-30-10 contactors:

Control Sequence

START pressed → KM1 + KM2 energize (Star)
     ↓
Timer delay (adjustable 5-15s)
     ↓
KM2 de-energizes, KM3 energizes (Delta)
     ↓
Motor runs at full speed
     ↓
STOP pressed → All contactors de-energize

Safety Features

• Mechanical & Electrical Interlocking between KM2 and KM3 (prevents simultaneous activation)
• ABB MS450 Motor Protection with overload and short-circuit protection
• Emergency Stop functionality via red push button
• Status Indication with pilot lights (green = running, yellow = starting)

3D CAD Design

The complete electrical panel was modeled in Autodesk Inventor Professional, featuring:

Component Integration

• All electrical components modeled with accurate dimensions
• Real manufacturer CAD data (ABB, Schneider Electric, Legrand)
• Wire routing using Cable & Harness module
• DIN rail mounting system

Enclosure Specifications

Internal Layout

The panel features organized component placement:

• Upper section: Circuit breakers and motor protection
• Middle section: Contactors and timer relays
• Lower section: Terminal blocks for field wiring
• Wire ducts: GARVIM 25×30mm for cable management

Electrical Schematics

Control Circuit

The control circuit includes:

• Start/Stop push buttons with maintained logic
• Timer relays for star-to-delta transition
• Auxiliary contacts for interlocking and status indication
• Overload relay contact for motor protection trip

Power Circuit

The power circuit handles:

• Three-phase power input through circuit breakers
• Motor starter protection via ABB MS450
• Contactor switching for star-delta configuration
• Six-wire motor connection (both ends of each winding accessible)

Bill of Materials

The complete BOM includes components from major industrial suppliers:

Control Components (Legrand)

• Push buttons (non-illuminated, green/red)
• Pilot indicators (24V, green/yellow)
• Timer relays (on-delay, adjustable)
• Miniature circuit breakers

Power Components (ABB)

• MS450 Manual Motor Starter (adjustable thermal overload)
• A40-30-10 Contactors (40A, 3-pole, 1NO auxiliary)
• HK1 Auxiliary Contact Blocks

Enclosure System (Schneider Electric)

• NSYS3D4320 Spacial S3D enclosure
• NSYDLM24 Modular DIN rail chassis
• NSYMB43 Mounting back plate
• NSYTRV62 Screw terminal blocks

Documentation Deliverables

The project includes complete technical documentation:

1. Design Memory - Calculations, component selection rationale
2. Power Circuit Diagram - Main circuit with contactor arrangement
3. Control Circuit Diagram - Logic and interlocking circuits
4. Terminal Block Diagrams - Field wiring reference (2 sheets)
5. Panel Door Layout - Front panel component positions
6. Equipment Disposition - Internal component arrangement
7. Bill of Materials - Complete parts list with references
8. 3D CAD Assembly - Full parametric model

Design Software

Skills Demonstrated

• Electrical Design: Motor control circuits, protection coordination
• 3D CAD Modeling: Complex assemblies, wire routing, technical documentation
• Industrial Standards: IEC/NEMA compliance, IP/IK ratings
• Component Selection: Matching specifications to application requirements
• Technical Documentation: Professional engineering deliverables

Applications

This star-delta starter design is suitable for:

• Industrial pumps and compressors (5-50 HP range)
• Conveyor systems with moderate starting torque
• HVAC equipment (fans, chillers)
• Manufacturing machinery requiring reduced starting current

The modular design allows adaptation to different motor ratings by selecting appropriate contactors and protection devices.