Gates Australia Pty Ltd -
By its definition, power transmission is the movement of energy from its place of generation to another point where it is applied to perform useful work. Any loss of power is a loss of money for users. To minimize losses and keep energy consumption in check, power transmission drives must operate at optimum efficiency. This paper compares the efficiency-related characteristics of two belt drives – V-belt drives and synchronous belt drives – to show the potential for savings.
Energy Efficiency Defined
Efficiency of any power transmission system is a measure of the power loss associated with the motor, the bearings and the belt drive. It is defined by the following formulas:
Efficiency = HP
out /HPin
Efficiency = (TORQUE
out x RPMout )/(TORQUEin x RPMin )
As these equations show, energy losses in belt drives are separated into two categories: torque loss and speed loss. These losses vary in V-belt and synchronous belt drives as a result of the belts’ inherently different
physical characteristics.
V-belt drives are a popular power transmission solution because of their low acquisition costs and wide availability.
Synchronous belt drives are an alternative to V-belt drives (and roller chain drives) when plant maintenance managers and design engineers are changing out metal components or designing a new
system.
Comparing Synchronous Belt and V-belt Drives for Energy Efficiency
One factor impacting torque loss is that heat is generated due to the friction between the belt sidewall andthe groove surface of the metal. V-belts depend on friction as they are part of a wedging mechanical system and therefore have greater energy loss due to heat generation than a synchronous drive, which has positive engagement between the belt tooth and sprocket groove and is generally cooler running. Another form of torque loss comes from the energy required to bend a belt around a sprocket or sheave. The thinner cross section of a synchronous belt requires less energy to bend than the thicker cross section of a V-belt.
Speed loss is also a characteristic of V-belt drives. A positive tooth/groove engagement prevents a synchronous belt drive from slipping, while V-belt drives, no matter how well maintained, will exhibit some amount of slip. Slip occurs when the tension is insufficient to transmit the load. V-belts elongate and require retensioning on a regular basis while synchronous belts have minimal elongation. Given these characteristics, a V-belt drive initially operates at 94-97% efficiency and can deteriorate up to
5% during regular operation. Poorly maintained V-belt drives can become as much as 10% less efficient. In contrast, a synchronous belt drive operates at a constant 98-99% efficiency, and on average, is 5% moreefficient than a V-belt drive1.
For more information about energy efficiency, please visit:
www.gatesprograms.com/efficiency.
Copyright ® 2008 Gates Corporation 1 http://www.gates.com/
