Drive technology stops sagging

Wausau, WI--Uneven web speeds on laminating coaters result in material sags, wrinkles, jams, or tears. That's why Wasau Coated Products' new laminating center uses 16 ac drives with Allen-Bradley Force Technology(TM). The field-oriented control ac-drive technology independently regulates motor speed and torque and reportedly delivers performance that rivals or exceeds that of dc motors.

The technology--a multi-patented field-oriented control scheme designed to separate and control torque- and flux-producing current--precisely controls machine roller speed. Field-oriented control allows ac drives to separate and independently regulate both flux and torque components while also controlling the orientation of these two components with respect to each other.

According to Allen-Bradley's Standard Drives Business Product Manager Cary Hiller, field-oriented control is the highest performance ac-drive technology available. Advantages include a high bandwidth for excellent response times, and constant torque regardless of changes in motor temperature.

While top performance may require a motor-mounted feedback device, this technology offers several other advantages:

- It replaces the V/Hz core of other vector drives with a high-bandwidth current regulator that separates and controls the flux and torque components of the stator current.

- It offers an encoderless version that eliminates the need for motor feedback, while providing both speed and torque control.

- It auto tunes itself by evaluating standard motor parameters.

- It helps reduce motor temperature because the ratio of motor current to motor torque remains relatively constant.

Typical applications include web-tension control at paper mills, and applications that require roll-unwind speed compensation and torque control to maintain constant tension at changing speeds.