Mercotac® Learning Center

Rotational Characteristics

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What engineers need to know about the rotational characteristics of Mercotac brushless slip rings.

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Technical Info.

This page is specifically designed for engineers who need to understand the rotational characteristics of Mercotac brushless slip rings. It provides detailed information on how to mount and use the slip rings in different rotational applications, along with important factors to consider such as maximum RPM rating, temperature limitations, and rotational torque. The page is a valuable resource for engineers who need to select and apply slip rings in their designs.

Learn about Mercotac® Rotational Characteristics

Mercotac Brushless Slip Rings will function while stationary or while under rotation. It is preferable to mount the Mercotac so that the body rotates to minimize the load on the bearing. To learn more about how to attach to the Mercotac, see the Mounting Page.

Mercotac’s can rotate in either direction and can be used between 0 RPM up to the maximum RPM speed rating of the specific model. The RPM can be constant or varying. It can also be used in bidirectional applications where the direction of rotation changes. The rotational drive mechanism should be axially-aligned and free of wobble/vibration. The attachment of wires/cables should be adequately strain relieved but not taut so as to not to induce rotational drag, vibration, or side loads on the bearings. Eccentricity of the mounting should be less than .005” TIR (total indicated runout).

The maximum RPM rating will vary by model but generally larger models have lower maximum RPM ratings. Due to internal friction from seals, bearings, and other internal components, faster RPM's will generate more heat. This rotational heat must be taken into account along with the ambient temperature, the current induced temperature rise, and any heat conducted into the Mercotac so as not to exceed the maximum temperature rating, which can cause failure. Also exceeding the maximum RPM can cause open channels or contacts.

Rotational torque is defined as the amount of torque (or rotational force) required in order to start rotating a Mercotac Brushless Slip Ring from a stationary state. With any rotating object, there is usually friction between rotating surfaces typical of the friction associated with bearings and bushings. Torque is required to overcome the static friction in order to begin turning a Mercotac unit. The rotational torque specification is an estimate, and can vary slightly with individual units.

The initial start-up or “break-away” torque will be higher than the immediate subsequent “running” torque. The drag force from the internal fluids and friction from internal components will cause more rotational torque at higher speeds. The rotational torque of Mercotac Brushless Slip Rings typically lessens after an initial break-in period and should remain fairly constant thereafter.

The rotational torque ratings for Mercotac products are in gram-centimeters (gf-cm). This rating is based on ideal laboratory conditions.

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