Why can something as simple as copper wire winding determine the fate of an industrial motor worth tens of thousands of yuan? In the three-phase induction motor stator winding process, those precisely arranged enameled wires hide deep electromagnetic secrets. This article reveals the complete process—from the pretreatment of three-phase stator and rotor cores to final varnishing and curing.
Preparation Before Winding
Materials
Enameled copper wire (diameter 0.04–11.68mm): The core conductor for electromagnetic conversion
Insulating paper (0.2mm thick): Prevents short circuits between windings
Slot wedge (epoxy resin): Secures the windings in the slots
End lashing strap (polyester fiber): Acts as a “seatbelt” for the windings
Equipment and Tools
Winding jig: Controls coil shape precisely
Common winding tools: Diagonal pliers, scissors, wrenches, calipers
Inspection tools and instruments: Micrometer, turn counter
Process Preparation
Prepare the required documents, materials, and tools for coil winding.
Check the wire diameter and place the copper wire spool on the rack.
Inspect the jig size and mount it on the main shaft of the winding machine.
Test run the machine to adjust speed and reset the turn counter.
Fix the enameled wire head to the winding jig, then tighten the wire to the proper tension. Ensure it is straight but not overstretched to avoid damaging the insulation.
Seven-Step Method For Stator Winding Of Three Phase Induction Motor
1. Stator Core Insulation Treatment
Blow away iron filings in the slots with compressed air.
Insert pre-cut insulation paper folded into a “U” shape into each slot, with the glossy side inward to aid wire insertion. We usually use NOMEX 410 paper.
2. Coil Winding
Leave the wire’s starting end at the specified length and fix it on a peg of the winding jig.
Start the winding machine. Arrange the wire from left to right in neat, tight layers without crossing.
Stop when the counter reaches the specified number of turns.
Leave a connection wire and repeat the process for the remaining coils.
Leave the end wire at the required length and cut it.
Remove the jig and take out each coil one by one. Bind both ends of each coil.
3. Coil Insertion
Lower Layer
Insert the pre-wound coil into the slots at a 30° angle. Use an insertion board to press the wire layer by layer, ensuring flat and even layers.
Take a 36-slot motor as an example: after inserting the lower coils, place 0.25mm NOMEX insulation paper in the slot. Fold the edges 3mm over the slot opening for extra protection. Insert the upper coils in reverse direction, adjusting the spacing between wires to within 0.5mm using a slot ruler.
Paper Trimming
Keep the compression bar in place and use a utility knife to trim off the excess insulation paper at the slot mouth, pushing from one end to the other. Then remove the bar.
Folding Insulation Paper
After removing the bar, fold the left-side insulation into the slot using the ruler tool. Push the paper in with the ruler at the front and the bar at the back. Repeat the same for the right-side paper.
Slot Wedge
As the bar is removed, insert the chamfered end of the epoxy resin slot wedge from the same side to complete sealing. The wedge should be 5mm longer than the core.
4. Three-Phase Induction Motor Stator Winding Ending Shaping
Use a nylon hammer with a silicone head to tap the coil ends outward from the center, shaping them into a trumpet structure with a 15°±2° angle. This reduces magnetic leakage and enhances airflow. Apply even force to avoid damaging the insulation.
5.UVW Termination
Refer to the winding layout to identify the U, V, and W phase start and end points. Use red, white, and black heat-shrink tubes to mark the leads. Connect them in either star or delta form.
Use a wire stripper to remove 15mm of insulation. Do not use blades to avoid damaging the copper wire. Weld the wires using silver-copper solder under an oxygen-propane flame.
Pull out lead wires ranging from 300mm to 10000mm according to the winding specification. Cover them with heat-shrink tubing for insulation.
6.Binding
Tie the coils with nylon rope to prevent them from slipping. Perform secondary shaping to ensure the windings do not extend beyond the core’s outer or inner diameter.
7.Varnish Dipping
Based on customer requirements, dip the stator into 180°C epoxy resin varnish for 30 minutes, then bake it at 120°C for 4 hours. A qualified insulation layer must pass a 1500V/1min withstand voltage test.
Rotor Winding for 3-Phase Induction Motor
The wound rotor’s structure closely resembles that of the stator. Medium-sized motors typically use a double-layer winding.
The three-phase rotor windings are star-connected. The three terminals connect to copper (or steel) slip rings mounted on the shaft, which communicate with external circuits via brushes.
Note that the rotor winding’s number of phases and pole pairs always match the stator. Each phase usually has more turns, creating a stronger induced voltage.
Winding Quality Control
Withstand Voltage Test
1500V AC for 60 seconds. Max leakage current between lead and core ≤ 5mA.
Resistance Test
Single-phase DC resistance ≤ 1.7Ω (at 20°C); resistance imbalance among phases ≤ 5%.
Inductance Test
Phase inductance deviation ≤ 15%.
Why Do Simple Wire Windings Power a Motor? The key lies in the clever interaction between stator and rotor. The stator coil layout determines magnetic field strength. Rotor bar spacing affects smooth operation. Even slight misalignment can cause overheating or jamming.
Choose Lamnow for Your Motor Winding
Lamnow is a leading manufacturer of motor stator and rotor in China. We specialize in both rotor and stator coil winding, offering both manual and automated processes.
We provide multiple insulation options before winding, including NOMEX 410 paper, epoxy coating, and injection-molded insulation (including 3D-printed versions). We support single-path, dual-path, or multi-parallel winding.
Whether it’s BLDC stator winding, three-phase induction motor stator winding, frameless torque motor winding, coreless winding, or PMSM winding—we’ve got it covered.
If you need motor stator or rotor cores, feel free to contact us.
