Wrapped belts could be considered the standard v-belt. The term wrapped comes from fabric that covers the internals of the belt, giving it a very uniform look and feel, as well as reasonably quiet operating characteristics.
The purpose of the wrap is two-fold. The fabric provides abrasion resistance, which makes the belt more durable. The contact between the belt and sheave is constant and can occur at very high speeds. This extra protection against contamination and wear of both belt and sheave, allows the belt to operate longer before it becomes too worn to transmit the required power properly.
Another benefit, which can be critically important in the applications that require it, is belt slip. While a v-belt slipping within a sheave can seem counter-intuitive, it can prevent significant damage. When a torque spike occurs, or a sudden change in the drive speed causes the belt drive to respond in kind, a wrapped belt will slip more easily than a raw-edge. Most of the time, the belt will snap before transmitting power back into the gearbox or motor, so the belt’s ability to slip is a safety factor.
Lastly, the fabric wrapping has high oil resistance. Raw edge belts have a possibility of becoming clogged with contaminants and absorbing moisture. This will lead to swelling of the belt rubber and cause breakage.