What the slip ring has to handle
- Low-voltage power collectors (230-500 V) at tens to hundreds of amps, or medium-voltage collectors (10-20 kV and above)
- Fibre optic rotary joint matched to the fibres in the reeling cable for automation data
- Fieldbus or Ethernet options for lower data rates where fibre is not used
- Enclosed housings, typically IP55 or better, with anti-condensation heaters for cold or fluctuating climates
- Ring count matched to cable cores (power, earth, control)
- Rugged mounting to the reel shaft with access for brush inspection
- Hazardous-area versions where reels serve explosive atmospheres
Typical figures
| Voltage | LV 230-500 V; MV 10-20 kV (higher on request) |
|---|---|
| Current | LV collectors 10-1000 A; MV collectors 240 A |
| Data | PROFIBUS at 1.5 Mbit/s through special ring bodies; rotary data transmission up to 12 Mbps or 1 Gbps; fibre reels up to 400 Gbps |
| Fibre | 6, 12 or 18 fibre channels in reference installations |
| Ingress protection | IP55 standard enclosure (higher on request) |
| Heating | Heater recommended below -25 C or with rapid temperature swings |
Example figures from the published sources listed below. Your requirement may differ; an engineer will confirm against your duty cycle.
Recommended slip ring types
Standards to consider
- IEC 60204-32 - electrical equipment of hoisting machines
- ATEX / IECEx - for explosion-protected reel slip rings
- IEC 60529 - IP code for collector enclosures
The complete system
A slip ring rarely works alone. For cable reels & reelers it is usually specified together with:
- motorised reel drum
- torque motor or magnetic coupling drive
- reeling cable
- cable guide
- fibre optic transceiver
- speed/position encoder
Specifying these together avoids mismatched connectors, cable routes and feedback interfaces, and gives you one point of contact for the whole axis.
Common problems to design out
- Condensation causing tracking and insulation faults
- Overheating of high-current rings
- Fibre signal loss through the rotary joint
- Brush wear and carbon dust build-up
Series used in this application
Frequently asked questions
Can a cable reel slip ring carry medium voltage?
Yes. Reel collectors are offered for medium voltage, for example 10-20 kV at 240 A, with higher voltages on request. Low-voltage versions cover 230-500 V at up to around 1000 A.
How is data sent through a cable reel?
Either over special data rings for fieldbus (for example PROFIBUS at 1.5 Mbit/s) or, more often now, over fibre in the reeling cable with a fibre optic rotary joint on the reel. Fibre gives the highest bandwidth and immunity to interference.
Why do reel slip rings have heaters?
Outdoor reels see condensation when temperatures drop or swing quickly, which can cause tracking between rings. Anti-condensation heaters are standard on medium-voltage collectors and recommended below about -25 C.