3-Phase Squirrel Cage Induction Motor

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Results at a glance

Successful sustained operation with no load

208V 3-Phase

Fabricated with commercial transformer laminations

Made from scratch

000 turns of #20 AWG enameled wire

Hand-Wound Coils

Made with digital circuits and relays

Wye-Delta Starter

Overview

During my Power Electronics course, I designed and built a complete 3-phase Variable Frequency Drive entirely on my own. The system was controlled by a PIC16F18876 microcontroller, for which I wrote all firmware from scratch using only the datasheet — no libraries, no application notes, and no simulation model existed for this part.

I implemented sine-wave modulated PWM with a 42-point lookup table, achieving a frequency range from 1 Hz to 3800 Hz. The VFD successfully drove a 3-phase BLDC motor from 1 Hz up to 140 Hz. To maintain proper V/f ratio at higher speeds, I also designed and integrated a buck-boost converter (going beyond the original project requirements).

Starting on a protoboard, I later designed a custom PCB in EasyEDA (learning the tool in a single day under deadline pressure), had it manufactured in China, and assembled the final board with IGBTs, photocouplers, BJTs, and a 4-digit 7-segment display. The circuit featured push-button speed control and an array of LEDs that visually displayed the real-time PWM switching on the IGBT gates — an outstanding debugging and demonstration tool.

Development Process

3D Modeling & Planning

Designed the complete motor in 3D to determine exact dimensions, material quantities, and manufacturing feasibility.

Hand-Wound Coils

Wound all stator coils by hand using a custom 3D-printed winding jig for perfect turns and tension.

Stator Completion

Final assembly of the stator with all coils secured and wiring routed.

Magnet Wire Current Testing

Stress-tested the magnet wire by passing 10 A DC through it to determine its real-world current limit for 208 V operation.

Cutting Transformer Laminations

Precisely cut transformer steel sheets into the custom stator and rotor shapes using the 3D model as reference.

Stator Core & Coil Integration

Inserted and secured the hand-wound coils into the assembled stator core.

Magnetic Field Validation

Tested the stator’s rotating magnetic field using a free-moving magnet to confirm proper three-phase operation.

Final Motor Assembly

Completed mechanical integration of stator, rotor, and housing with all electrical connections.

Varnish Application

Applied insulating varnish to every individual lamination to prevent eddy currents.

Coil Terminal Wiring

Routed and terminated all coil leads for proper three-phase Wye configuration.

Rotor Preparation

Recycled and modified an existing rotor, then designed and 3D-printed an iron-filled PLA adapter to mount the squirrel cage bars.

First Successful Run

Powered up the finished motor and captured it running smoothly under full three-phase operation.

Lamination Organization

Applying varnish to each of the laminations

Continuity & Resistance Testing

Verified every coil for continuity and measured resistance to ensure balanced windings before final assembly.

Squirrel Cage Integration

Installed the custom squirrel cage windings onto the 3D-printed rotor adapter.

Stator Core Assembly

Assembled the complete stator core by pressing the individual laminations into a solid, rigid stack.

Acrylic Side Panels

Installed transparent acrylic sides to create a fully visible, educational motor housing.

Wye-Delta Starter Circuit

Built a Wye-Delta starting circuit on protoboard to safely start the motor at reduced voltage.

Technical Deep Dive