Electric Hoist Motor Winding Process Standards

Electric Hoist Motor Winding Process Standards

I. Winding Process - The "Heart and Veins" of Electric Hoist Motors

As core equipment for industrial lifting, electric hoists rely on motor performance to directly determine lifting safety and efficiency. Winding, a core step in motor manufacturing, acts like the "nerves and blood vessels" of the motor. Every wire layout, every layer of insulation, and every control of the number of turns must adhere to strict process standards. Substandard winding can lead to abnormal motor temperature rise, insufficient torque, and even short circuits and fires, posing a fatal hazard to lifting operations. This article combines industry standards such as JB/T 7085.2-1993 with practical experience to systematically analyze the full process standard for electric hoist motor winding.

II. Core Standards for Winding Processes

Electric hoist motors mostly use series-wound or asynchronous motor structures. Their winding process must meet both general standards and specific requirements for lifting equipment:

Basic Standard Framework

Strict compliance must be followed with "JB/T 7085.2-1993 Guidelines for Stator and Rotor Winding of Series-wound Motors for Electric Tools." This standard specifies the technical requirements, equipment specifications, and inspection methods for symmetrical rotor winding (H-type winding). Furthermore, compliance with the mandatory provisions for insulation performance and electrical clearances in GB 3883.1, "Safety of Handheld Power Tools," must be met.

Specific Requirements for Lifting Equipment

Compared to ordinary motors, electric hoist motors must withstand frequent starts and stops and load fluctuations. Therefore, the winding process places additional emphasis on three key points: first, wire tension control accuracy (within ±0.1N) to ensure coil tightness; second, a strict limit on the number of joints (no more than four per motor); and third, the insulation layer must meet a temperature resistance rating of F or above (withstands temperatures of 155°C).

III. Pre-Operation Preparation: Pre-Standards for the Winding Process

(I) Material Selection Standards

Wire Specifications

Preferably, enameled round copper wire should be used. The wire diameter tolerance must be within ±0.02mm (measured with a micrometer). Select the motor based on power: 1-3 ton electric hoist motors typically use 0.8-1.2mm Φ wire, while 5-10 ton models require 1.5-2.0mm Φ wire. The wire insulation must pass a scratch resistance test (no damage when scratched with a fingernail).

Insulation Material Specifications

The slot insulation utilizes a double-layer structure: an outer layer of 0.15mm green shell insulation paper and an inner layer of 0.15mm polyester fiber paper composite foil (DMDM). The length of the insulation paper extending beyond the core must match the motor specifications: for motors with a center height of 80-112mm, the extension is 6-7mm; for motors with a center height of 180-280mm, the extension is 12-15mm. This ensures that creepage distances meet standards.​
Supplementary Material Requirements

Binding cotton cord must be wax-impregnated (to improve wear resistance) and uniformly 10-15cm in length. The insulation sleeve of the connector must be at least 15mm longer than the overlapped portion of the conductor insulation.

(II) Equipment and Tool Calibration Standards

Core Equipment Specifications

A double-arm winding machine with a counter must be equipped with tension adjustment, slow start/stop, and braking functions. The winding machine spindle runout must be ≤0.03mm, and the counter error must not exceed ±1 turn. The tension device must be pre-calibrated: 3-5N for Φ1.0mm conductors and 8-12N for Φ2.0mm conductors.

Mold and Tool Standards

The dimensional tolerance of the winding die must be ±0.5mm, with a surface roughness Ra ≤0.2μm. After installation, the die core spacing must be verified with a caliper. Inspection tools must be calibrated regularly: the turns counter should be calibrated annually, and the micrometer should be calibrated every six months to ensure measurement accuracy.

IV. In-Operation Implementation: Full Winding Process Standards

(I) Standard Stator Winding Process

Pre-winding Test

Secure the wire reel on the wire rack. Pass the wire through the felt-lined clamping plate (to reduce insulation wear). Adjust the winding machine speed to 300-500 rpm (lower limit for thick wire). Wind 3-5 test coils. Use a turns counter to verify compliance before formal production begins.

Coil Winding Specifications

Leave 1/2 the coil circumference at the beginning and secure it to the winding die pin.

The wires must be arranged neatly and tightly, without any overlap. After every 10 turns, gently press the wires manually to prevent loosening.

Each coil must have no more than one joint, located on the beveled edge of the end. The surface after welding must be smooth and meet mechanical strength standards (no breakage when pulled).

After winding, tie the ends of the coil with cotton string, with a spacing of ≤50mm.

(II) Special Standard for Symmetrical Rotor Winding (H-Type Winding)

The rotor of an electric hoist series-wound motor must be symmetrically wound using a double-arm winding machine. The key steps are as follows:

Rotor Pretreatment

Confirm that the slot insulation is installed according to the design, the commutator is securely pressed, and the insulation end plates are free of deflection (the gap with the core is ≤0.3mm).

Symmetrical Winding Operation

Two enameled wires are drawn from the winding arms and wound simultaneously into two pairs of axially symmetrical slots. After winding, the rotor is rotated 180° to continue. During the winding process, a sliding template guides the wire path to ensure consistent coil shape.

Dynamic Tension Control

A high-precision sensor monitors the tension in real time. When the wire diameter deviates by ±0.05mm, the system automatically adjusts the tension (for every 0.01mm increase in deviation, the tension increases by 1N).

(III) Wire Insertion and Sealing Standards

Coil Arrangement Requirements

Use your thumbs to compress the coil width until it fits the stator bore. Flatten the lower edge into a "knife-like" shape (flatness tolerance ≤ 1mm) to avoid damaging the insulation during insertion.

Layered Wire Insertion Specifications

After inserting the lower edge, use a scriber to score the conductors in the slot (ensure they are parallel and not crossing). Then insert the interlayer insulation (ensure the width completely covers the lower coil). Before inserting the upper edge, press the lower conductors firmly. During insertion, use a scriber to cut each conductor into the slot to prevent them from popping out.

Slot Sealing Standards

First, use a scriber to press the conductors firmly into the slot (pressure should be kept between 5-8N). Trim any insulation paper protruding from the slot. Then fold the insulation paper into the slot. Finally, insert the slot wedge (3mm shorter than the slot insulation and ensuring a snug fit).

V. Post-Production Inspection: Acceptance Criteria for Winding Quality

(I) Routine Inspection Items

Basic Parameter Verification

Check the number of turns on each coil with a turns counter (deviation ≤ ±1 turn). Measure coil dimensions with a caliper (deviation from the drawing ≤1mm). Check wire diameter: Randomly select three coils from each batch and measure each coil at three locations. The tolerance must meet the required standards.

Appearance and Insulation Inspection

The coil surface must be free of insulation damage or wire crossover; the joints must be tightly wrapped, and the insulation sleeve must not be dislodged. Measure insulation resistance with a 500V megohmmeter: ≥50MΩ when cold and ≥10MΩ when hot.

(II) Special Performance Tests

Withstand Voltage Test

Apply 1500V AC voltage to the winding for 1 minute without breakdown or flashover (in compliance with GB 3883.1). Dynamic Simulation Test

After assembling the wound motor, it is subjected to 100 start-stop cycles, monitoring the winding temperature rise (≤80K) and torque output (fluctuation range ≤5%) to ensure compliance with the electric hoist load requirements.

(III) Standards for Handling Defective Products

Products with a turn deviation exceeding ±2 turns or insulation damage exceeding 1 point per coil are scrapped.

Products with loose connectors or slight crossover of wires may be reworked, but the number of reworks per coil shall not exceed one, and a full re-inspection shall be performed after rework.

VI. Implementation of Standards - The Cornerstone of Safe Electric Hoist Operation

Every standard in the electric hoist motor winding process represents a solemn commitment to hoist safety. From enameled wire selection to winding machine calibration, from coil winding to insulation testing, oversight in any step could lead to a safety incident. As a motor manufacturer, only by internalizing standards like JB/T 7085.2-1993 and integrating them with intelligent winding technologies (such as machine vision and remote equipment monitoring) can we continuously produce high-performance, high-safety motor products and safeguard industrial lifting operations.