As it relates to speed reducers, they all have some common similarities regardless of the application. Primarily they are used to transmit uniform motion when coupled to a type of motor (usually an electric motor). The transfer of power from the motor via the speed reducer will operate a wide variety of applications ranging from material handling conveyors to food processing equipment to personal mobility devices, just to name a few. When a request for a speed reducer is made, a joint effort between the Boston Gear sales engineering team in conjunction with the customer’s engineering team outline a set of specifications to determine the proper selection of a speed reducer under a given set of operational parameters. Mostly this is theoretical data based on a wide variety of assumptions.

So how do we know for sure if the reducer is properly selected and applied?
One easy way is to collect some data directly from a representative application. By having the user maintenance personnel take some amperage readings while the system is running, this information can be converted into horsepower and thusly verify that the Boston Gear speed reducer was properly selected.

To convert amperage readings into horsepower, consider the following formula.
HP= (A x V x 1.73 x Motor PF x Motor Efficiency) / 745.6 watts (converts watts to HP)
Whereas:
HP= horsepower converted from amp readings
A= amp draw under operating conditions
V= volts used to power the motor (typical 280, 460, 480, etc.)
1.73= 3 phase electrical power standard
Motor Power Factor = usually found on motor nameplate (typical ranges: .85-.95)
Motor Efficiency= usually found on motor nameplate (typical ranges: .90-.99)

Example:
Let’s say that our maintenance person used his “amp meter” to test the motor while the system was running under the typical application load conditions. He collected the following data:

V = 460
A= 5
Motor Power Factor from motor nameplate = .93
Motor Efficiency from motor nameplate = .95

Using the formula above we determine the following:
HP = (460 x 5 x 1.73 x .93 x .95) / 745.6 = 4.7149 or rounded to 4.7 HP

If the speed reducer selected has a rating higher than 4.7 horsepower then we could assume that we have a good application. To guarantee a good application we would use the service factor method. As an example, most material handling conveyor OEM’s require speed reducers to have a minimum of 1.25 service factor, and sometimes more, based on the exact application conditions. In using the 1.25 as a bench mark we could take the 4.7 HP as determined from our formula multiplied by 1.25. The result will be 4.7 x 1.25 = 5.875 (rounded to 6 HP) required to meet the application demands.
If the speed reducer is rated less than this example of 6 HP then we could anticipate premature failure. If the reducer greatly exceeds the example of 6 HP then it could be assumed the reducer is oversized for the application and instead offer a smaller reducer thus saving the customer money provided the change is acceptable by both parties. The golden rule is always providing the correct sized reducer for the application. When this occurs, all parties involved with the process are happy with the cost effective and technically sound solution provided.

Hopefully you found this article beneficial and will use these tools to increase success when solving power transmission challenges within your facility. Please email me with your comments at engineering@bostongear.com.