Rated Voltage 1.8/3kV and Below Variable Frequency Motor Cable

Implementation Standards

Since no national or industry standard for VFD power cables rated 1.8/3kV and below currently exists in China, manufacturers primarily follow these reference standards:
1. GB/T 12706: Extruded insulated power cables and accessories for rated voltages from 1kV to 35kV — electrical performance reference.
2. GB/T 19666: General rules for flame-retardant and fire-resistant electric cables.
3. Enterprise standards (e.g., Q/1521STD019-2020).
4. For marine and offshore applications: CB/T 4396-2014 "Power cables for variable frequency drives on ships and offshore installations."

Key Technical Features

1. Symmetrical Cable Structure

The most fundamental difference between VFD cables and ordinary power cables is the symmetrical structure. For VFD cables rated 1.8/3kV and below, while standard 3+1-core and 4-core cables can be used for main power input, cables connecting the VFD to the motor must use a symmetrical cable structure. Symmetrical structures are available in 3-core and 3+3-core configurations.

The 3+3-core structure divides the fourth conductor (neutral) of the traditional 4-core cable into three smaller-section insulated conductors, forming a symmetric 6-conductor arrangement (three large + three small). This symmetric layout improves interchangeability and electromagnetic compatibility, cancels odd harmonics, enhances noise immunity, reduces electromagnetic radiation, and lowers wave impedance and reflection.

2. Shielding Structure

Shielding is another critical technical feature of VFD cables. For 1.8/3kV and below VFD cables, an overall shield structure is commonly used. Available shield configurations include: copper wire + copper tape composite shield, copper wire braid shield, copper tape shield, and copper wire braid + copper tape shield.

The shield cross-section is designed in proportion to the main conductor cross-section. This shielding structure provides effective protection against electromagnetic induction, poor grounding, and power line conducted interference. It also serves as a channel for short-circuit current, functioning like a neutral conductor protection.

3. Electrical Performance

Key electrical performance parameters for 1.8/3kV and below VFD cables:

Product Structure

Typical VFD cable structure (overall shield type) from inside to outside:
1. Conductor: Multi-strand oxygen-free copper wire; resistance per GB/T 3956.
2. Conductor shield (some designs): Semi-conductive shield between conductor and insulation.
3. Insulation: Cross-linked polyethylene (XLPE) or similar high-performance material. 1.8/3kV cables often use 10kV-grade XLPE insulation material.
4. Insulation shield (some designs): Semi-conductive shield over insulation.
5. Overall shield: Copper tape, copper wire braid, or composite shield.
6. Inner sheath (if applicable).
7. Outer sheath: PVC or low-smoke halogen-free polyolefin.

Common Model Types

Specification Range

Operating Characteristics

Working Temperature:
- XLPE insulation: Max long-term conductor temperature 90°C; short-circuit max 250°C.
- PVC insulation: Max long-term conductor temperature 70°C.

Installation Conditions:
- Installation temperature: Not lower than 0°C (preheat if below 0°C).
- Min. bending radius (unarmored): >= 15D (D = cable outer diameter).

Application Scope

1. Connection cables between VFD power supplies and variable frequency motors.
2. AC 0.6/1kV or 1.8/3kV power supply or main circuit connection cables.
3. Pumps, fans, conveyors, transfer lines, and HVAC equipment in paper, steel, textile, metal processing, food processing, mining, railway, metallurgy, power, and petrochemical industries.
4. Cables connecting inverters to motors on ships and offshore facilities (must comply with CB/T 4396-2014).

Cable Selection Guide

Core Count Selection:
- Power transmission only: 3-core symmetrical cable.
- With neutral or ground wire: 3+3-core symmetrical cable for optimal EMC performance.

Shielding Type Selection:
- General EMC environment: Single-layer shield (copper wire braid or copper tape).
- Strong EMI environment: Double shield (copper wire braid + copper tape).
- Flame-retardant requirement: Add "ZB" (Grade B) or "WDZ" (LSZH) prefix.
- Fire-resistant requirement: Add "NH" prefix.

Important Note: VFD cables and ordinary power cables should not be used interchangeably. The symmetrical structure and dedicated shielding design of VFD cables are essential for stable VFD system operation. Using standard cables in VFD systems may cause electromagnetic interference, accelerated insulation aging, and motor noise.