Detailed Description
How an Elevator Traveling Cable Works
An elevator traveling cable is one of the most mechanically demanding cable applications in existence — not because of high voltage or high current, but because of the sheer number of bending cycles.
In a typical passenger elevator serving a 20-floor building, the car makes approximately 500–1 000 trips per day. Each trip involves the cable bending at the shaft midpoint — the point where the cable transitions from the moving car to the fixed building wiring. Over a 20-year service life, the cable experiences 3–7 million bending cycles. For a high-rise office building with 50 floors and 2 000 trips per day, that number can reach 15 million cycles.
The traveling cable connects the elevator car — which moves — to the fixed electrical supply at approximately the midpoint of the shaft. One end of the cable is fixed to the car (typically at the car top junction box). The other end is fixed to the shaft wall at the midpoint. As the car moves from the bottom floor to the top, the cable flexes at the midpoint suspension point, effectively doubling over on itself. The cable must handle this continuous flexing without conductor breakage, insulation cracking, or jacket failure.
Core Allocation in a Standard Elevator Traveling Cable
A 24-core elevator traveling cable (a common configuration for mid-rise passenger elevators) is typically allocated as follows:
| Core Group | Core Count | Cross-Section | Function |
|---|---|---|---|
| Car lighting | 2 | 1.5 mm² | 220 V AC car light power |
| Car fan/ventilation | 2 | 1.0 mm² | Fan motor power |
| Door operator | 3 | 1.0 mm² | Door open/close motor + common |
| Call buttons | 4 | 0.75 mm² | Floor call button signals (up/down, 2 wires each) |
| Floor indication | 2 | 0.75 mm² | Floor position signal to car display |
| Intercom | 2 | 0.5 mm² | Car-to-machine room voice communication |
| Safety circuit | 2 | 1.0 mm² | Door lock safety circuit (series loop) |
| Emergency light/alarm | 2 | 0.75 mm² | Battery-backed emergency lighting and alarm |
| Inspection control | 2 | 0.75 mm² | Car top inspection station control |
| Spare | 3 | 0.75 mm² | Future expansion; mandatory in most elevator standards |
Additional cores are added for: CCTV camera (coaxial or twisted pair), access control card reader, emergency telephone auto-dialer, load weighing sensor, destination dispatch keypad, and building management system (BMS) interface. A modern high-rise elevator with all these features may require 48–60 cores.
Steel Wire Suspension — Why the Cable Cannot Support Itself
An elevator traveling cable spans the distance from the shaft midpoint to the car's lowest position. On a 20-floor building (≈60 m shaft height), the midpoint is at 30 m. The cable drop from the midpoint to the car — when the car is at the bottom floor — is approximately 30 meters. The cable's self-weight over this free-hanging span would elongate the copper conductors and eventually cause fracture.
The integrated galvanized steel wire suspension elements (typically 2–4 wires distributed across the flat cable width) carry this weight. The steel wires are anchored:
- At the shaft midpoint connection box: Via dedicated strain relief clamps attached to the building structure
- At the car top junction box: Via strain relief clamps attached to the car frame
Yichi Elevator Traveling Cable Quality
- Conductor strand count verified: IEC 60228 Class 5 specifies minimum strand count per cross-section. We verify strand count on every production batch — insufficient stranding leads to premature fatigue fracture
- Steel wire pre-straightened: Steel suspension wires are mechanically pre-straightened before cable assembly — residual curvature causes uneven tension distribution between wires
- Parallel conductor pitch controlled: Conductor spacing across the flat cable width is controlled to ±0.3 mm — uneven pitch causes irregular bending stiffness that concentrates fatigue at specific conductors
- Bend life tested: Sample cables tested on a reciprocating bend test machine — >3 000 000 cycles at 400 mm bend radius without conductor breakage. Acceptance criterion: zero conductor failures, <10% increase in conductor resistance