Detailed Description
One Cable Instead of Three — The Integration Argument
A modern overhead crane with VFD hoist control, encoder feedback, and load cell weighing requires at least three separate circuits from the control panel to the trolley:
- Circuit 1: 4-core power cable — hoist motor (U/V/W/PE)
- Circuit 2: multi-core control cable — brake, limit switches, thermal sensors
- Circuit 3: shielded signal cable — encoder feedback, load cell signal, VFD control signals
The combined cable integrates all three circuits — plus optionally fiber optic for crane CMS, CCTV, or network connectivity — into one cable on one drum with one gland. The installation effort is reduced by approximately two-thirds.
PET Fleece Separation — Why It Is Necessary
Mixing power, control, and signal conductors in one cable creates the potential for two problems:
1. Electromagnetic Interference (EMI)
A 50/60 Hz power conductor carrying 50–200 A generates a magnetic field that induces voltage in adjacent signal conductors. A 4–20 mA load cell signal or a millivolt-level thermocouple signal cannot tolerate induced noise from adjacent power conductors.
Solution: The shielded signal pairs use individual tinned copper braid shields (≥85% coverage) that create a Faraday cage around each pair — the induced current flows in the shield, not the signal conductor. The signal pairs are also physically separated from the power cores by a PET fleece layer, increasing the distance and reducing the magnetic coupling.2. Mechanical Abrasion
During reeling, conductors move relative to each other as the cable bends. Power conductors — larger, heavier, and subject to more force — abrade the thin insulation of adjacent control and signal conductors.
Solution: The PET fleece layer creates a defined separation plane between functional groups. Power cores move against the fleece, control and signal cores move against the other side — they never touch each other.Shielded Signal Pairs — What They Carry
| Signal Type | Pair Count | Cross-Section | Shield | Application |
|---|---|---|---|---|
| Encoder feedback | 2–4 pairs | 0.22–0.34 mm² | Individual braid | VFD closed-loop motor control |
| Load cell | 1–2 pairs | 0.34–0.50 mm² | Individual braid | Crane weighing system |
| Analog sensor | 1–2 pairs | 0.22–0.50 mm² | Individual braid | Temperature, vibration, position |
| RS-485 / CAN bus | 1–2 pairs | 0.22–0.34 mm² | Individual braid + foil | PLC communication |
| CCTV (coax substitute) | Via fiber | SM fiber | n/a (optical) | Crane camera system |
Why Choose Yichi Combined Overhead Crane?
- In-house fiber capability: Fiber optic integration done in our own production — tested for attenuation before and after cabling
- PET fleece on every functional boundary: Not just power-to-control — every functional group is separated, including signal pairs from each other
- Shielded pairs as standard: Encoder and load cell signals require shielding — not an option, part of the cable design
- Simplified installation: One cable, one drum, one gland — reduces installation time by two-thirds vs three separate cables