High-current slip rings
Mercotac Model 1500 (and 1250) high-current slip ring
Single-conductor liquid-metal rotating connector for 500 A at up to 300 rpm with under 1 mΩ contact resistance, in a stainless steel body; the Model 1250 is the 250 A version.
Key specifications
| Circuits (max) | 1 |
|---|---|
| Current per circuit (max) | 500 A |
| Speed (max) | 300 rpm |
| Ingress protection | IP51 with external dust seal |
| Temperature | -29–60 °C |
| Contact resistance | <1 mΩ |
| Torque | 750 gf-cm max |
| Body | stainless steel |
Summarised in our own words from Mercotac, Inc.'s published data; series maxima, individual models vary. Last checked 2026-10-30. Source 1 · Source 2
Notes on this data
Mercury-wetted (liquid metal) contacts: Mercotac states the connectors contain a small amount of elemental mercury and cannot be said to conform to RoHS; EU users must check exemptions and national rules. Voltage listed as N/A for the 1500.
Specify Motion is not affiliated with Mercotac, Inc.. Mercotac and Model 1500 (and 1250) are used only to identify the product. Comparisons use published figures; always confirm against the current datasheet.
Typical applications
Alternatives that meet or exceed these figures
Engineers often come to us with a Mercotac part number and leave with an alternative that is easier to source, quicker to deliver or a better fit for the machine. These series from our supply network is the closest match on published figures.
Heavy-duty carbon-brush slip rings for very high current and voltage, with copper-graphite power rings and precious-metal signal rings. Large and heavy by design, but straightforward to maintain.
| Published maximum | Model 1500 (and 1250) | BHR Series Frameless Type (Carbon Brush) |
|---|---|---|
| Circuits | 1 | 76 meets or exceeds |
| Current per circuit | 500 A | 500 A meets or exceeds |
| Speed | 300 rpm | 10 rpm |
| Voltage | — | 20,000 V |
Figures are the highest published for each series and are not always measured the same way. A higher figure is not automatically a better choice: mounting, duty cycle, feedback, connectors and approvals matter too. An engineer will check the fit against your application before recommending anything.
What a high-current slip ring is
A high-current slip ring is a rotary joint built to carry heavy power, typically tens to hundreds of amps per circuit, across continuous rotation. Instead of fine precious-metal wires, it uses wider rings in copper alloy or brass and brushes in copper graphite or silver graphite, sized to keep current density and contact heating within limits. Ring spacing and insulation are increased for higher working voltages. Many designs also carry low-level signal rings on precious-metal contacts in the same assembly, separated from the power section.
When engineers choose a high-current slip ring
Choose a high-current design when motors, heaters, magnets or welding equipment on the rotating side draw more than a standard ring can handle. It suits cranes, cable reels, welding positioners and heavy turntables. The trade-offs are size, weight, drag torque and brush dust: carbon-based brushes wear and need inspection, so maintenance access matters. Where rotation is limited to a few turns, a cable carrier or cable wrap may still be simpler. Keep sensitive signals physically separate from the power rings.
How to specify the Mercotac Model 1500 (and 1250)
Send these with your enquiry and an engineer can confirm the right Model 1500 (and 1250) variant or an equivalent:
- Current per circuit, continuous and peak (A)
- Working voltage and required insulation level (V)
- Duty cycle and ambient temperature (°C)
- Speed, continuous and peak (rpm)
- Number of power circuits plus any signal or earth circuits
- Bore, envelope and mounting (mm)
- Brush inspection interval and maintenance access
Common mistakes to avoid
- Quoting the motor nameplate current but not the inrush or peak current at start-up
- Ignoring temperature rise in an enclosed housing, which derates current capacity
- Placing encoder or fieldbus rings right next to high-current motor feeds
- Leaving no access to inspect brushes and clean carbon dust
Mercotac Model 1500 (and 1250): frequently asked questions
What is the Mercotac Model 1500 (and 1250)?
Single-conductor liquid-metal rotating connector for 500 A at up to 300 rpm with under 1 mΩ contact resistance, in a stainless steel body; the Model 1250 is the 250 A version. Published series figures include circuits 1, current per circuit 500 A, speed 300 rpm, temperature -29 °C. It is made by Mercotac, Inc.; Specify Motion can help source it or propose an equivalent.
Who makes the Mercotac Model 1500 (and 1250)?
The Mercotac Model 1500 (and 1250) is made by Mercotac (Mercotac, Inc.) and is listed here for engineers comparing options. Specify Motion is not affiliated with Mercotac, Inc.; brand names are used only to identify the product.
What is the circuits of the Mercotac Model 1500 (and 1250)?
The published series maximum circuits is 1. Individual models and sizes in the Model 1500 (and 1250) range vary, so check the exact variant against your duty cycle, mounting and environment, or ask our engineers to confirm the right size for you.
Is there an alternative to the Mercotac Model 1500 (and 1250)?
Yes. On published figures, BHR Series Frameless Type (Carbon Brush) is the closest match from our supply network. An engineer confirms the fit against your application before recommending anything.
Why do high-current slip rings use carbon brushes rather than gold contacts?
Gold-wire contacts suit low currents because they give very low noise, but they cannot carry heavy current without overheating. Copper graphite and silver graphite brushes offer a large contact area, good conductivity and self-lubrication, which handles tens to hundreds of amps. The trade-off is brush wear and dust, so these units need inspection intervals and sensible enclosure design.
How much current can one slip ring circuit carry?
It depends on ring size, brush material, speed, ambient temperature and duty. Standard capsules typically manage a few amps per ring, while dedicated high-current units are commonly rated from tens of amps to several hundred amps per circuit. Always quote continuous, peak and duty cycle together, because a ring that is fine at 50% duty may overheat when run continuously.
Further reading: How to select a slip ring · How to specify a slip ring · Slip rings
Other high-current slip rings series
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