As a 630KW high-voltage motor, its wiring technology differs fundamentally from low-voltage systems. In high-voltage environments, insulation reliability, electrical clearance, and mechanical protection are the three core control points. Any oversight in details can trigger breakdowns, discharges, or even short circuits. Below, we discuss typical wiring issues in high-voltage motors from the professional perspective of Xi’an Simo Motor, combined with analysis of the following points:
High-Voltage Motor Phase Handling and Insulation Protection
Heat-Shrink Tubes vs. Insulation Tape
Three-phase terminal lugs (“cable noses”) are recommended to use color-coded heat-shrink tubes (e.g., yellow/green/red for phases A/B/C) instead of insulation tape. Heat-shrink tubes offer higher temperature resistance (typically ≥125°C), insulation strength (≥2500V), and anti-aging properties, with clear color coding for easy maintenance.
Fireproof Putty Sealing
Cable entry/exit points must be tightly sealed with fireproof putty (e.g., organic firestop material) to form a fireproof barrier. This prevents moisture intrusion (critical for high-voltage systems sensitive to humidity), blocks small animals from causing short circuits, and complies with fire safety regulations.
High-Voltage Motor Phase Length and Bending Radius
Excessive Length of AC Phase Cable Ends
The current AC phase cable ends have excessive reserved length, bringing uninsulated conductor parts too close to the metal casing of the terminal box (insufficient safety distance). It is recommended to precisely cut cables according to actual wiring needs (simulate layout with dummy cables first), leaving a moderate margin (usually ≤50mm) to avoid redundant cable accumulation.
Non-Compliant Bending Radius
Excessively small cable bending radii can cause mechanical damage to insulation layers, potentially leading to partial discharge during long-term operation. According to GB 50168-2018 Cable Line Construction and Acceptance Standards for Electrical Installations, the minimum bending radius for high-voltage cables should be ≥15 times the cable’s outer diameter (for cross-linked polyethylene insulation). If space is limited, install right-angle copper busbars to change connection angles and reduce bending stress.
Anti-Oxidation and Contact Reliability
Tinning Treatment for Terminals
The contact area between cable ends and flat washers should be tinned or 搪锡 (tinned with solder) to prevent oxidation of copper conductors, which can increase contact resistance by 5–8 times. Silver-containing solder (low melting point, high conductivity) is recommended to ensure smooth, burr-free surfaces.
Screw Tightening and Thermal Imaging Inspection
Joints must be tightened with a torque wrench according to specifications (e.g., M10 bolts: 44–54N·m). Before operation, use infrared thermal imaging to detect temperature rise, ensuring joint temperature does not exceed ambient temperature by 40K (per GB 755-2019 standards).
Missing Shielding Layer Grounding
Ungrounded Shielding Layer
The metal shielding layer of high-voltage cables must be reliably grounded (single-end or double-end grounding, depending on the system); otherwise, induced voltage may 击穿 (break down) the insulation. The correct approach is to connect the shielding layer to the motor casing via a grounding terminal, with grounding resistance ≤4Ω and grounding wire cross-sectional area ≥25mm² (copper).
Inadequate Mechanical Protection
Snake Tube and Insulation Sheath
Exposed cable segments from ground conduit to the terminal box must be covered with snake tubes (e.g., galvanized metal flexible conduit) to prevent mechanical damage, and insulated with silicon rubber sheaths to cover exposed conductors, ensuring electrical clearance ≥125mm (standard for 10kV systems).
Insulation Process Defects
Risk of Main Insulation Exposure
When fabricating cable ends, the stripping length of the main insulation layer must strictly follow process requirements (typically terminal crimping length + 10mm) to avoid excessive conductor exposure. If insulation damage occurs, repair with high-voltage self-adhesive insulation tape (e.g., 3M 23#) in multiple layers, with thickness ≥ the cable’s main insulation layer.
Standardized Operation Guidelines for Xi’an Simo High-Voltage Motor Wiring
Pre-Construction Preparation
- Verify cable specifications (voltage class, cross-sectional area) match the motor nameplate.
- Use a cable phase detector to confirm phase sequence and avoid errors.
- Prepare specialized tools: cable strippers, crimping pliers, heat guns, insulation resistance testers.
Key Process Steps
- Strip cable outer sheath → 2. Weld shielding layer grounding wire → 3. Crimp terminals → 4. Shrink insulation layer → 5. Install phase color tubes → 6. Conduct overall withstand voltage test (recommended: 2.5U₀ DC withstand voltage test for 15 minutes).
Acceptance Criteria
- Insulation resistance ≥1000MΩ (measured with a 2500V megohmmeter).
- Clear phase markings and reliable grounding.
- Electrical clearance and creepage distance comply with GB 14711-2013 General Safety Requirements for Small and Medium Rotating Motors.
Summary of Current Issues: The main problems focus on process standardization and protective integrity, particularly the handling of AC phases, shielding grounding, and mechanical protection, which require immediate rectification. As core industrial equipment, high-voltage motor wiring must adhere to the principle of “strict precision and insulation priority.” It is recommended to have certified high-voltage electricians perform the work, and retain construction records and test reports to ensure long-term stable operation.
