must operate dependably despite the high temperatures, plastic dust and, in many cases, space constraints that all put demands on electric motors. The question is: How can processors maximize the dependable operation of the electric motors that drive extruders? The question applies to all extruded products, whether pipe, profile and tubing, sheet or film.
He does not see particular performance advantages for any one motor type, regardless of the type of product being extruded. He says that the company designs a 15 percent safety factor into its extruders for the amount of torque required, regardless of the type of motor used. “As things wear, as the life of the extruder goes on, you will need to turn up the speed of the extruder and take advantage of that safety factor,” he says.
Proponents of the laminate-frame AC motor design — which uses sheets of steel that are stacked to create the core of the motor — cite features that they say make it particularly well suited for extrusion applications. The motors can be installed on original equipment and used as retrofits.
• Low profile, making them a good choice for situations in which space is an issue.
• High power density with the ability to run at a low temperature.
• Low inertia, with the ability to perform at an extended speed-versus-torque range, and high overload capacity at zero speed.
• The versatility to run different resins through the same extruders.
Heat is the enemy of electric motors. Of the three temperature-rise classes, which reflect safety margins — H (a rise of 356 degrees Fahrenheit
), F (311 degrees Fahrenheit
) and B (266 degrees Fahrenheit
) — Class B motors are the largest. Of the three major insulation classes — the insulation that a motor requires for a certain temperature rating — motors with Class H insulation can operate at the highest temperatures.