Design News for Mechanical and Design Engineers

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.

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.