Drives cut downtime

Dec. 11, 2003
Ac drives relieve dc motor and drive service issues.
The V7 sensorless vector ac drive has a keypad program rewrite or can run a verify routine to check for changed parameters. A copy function lets drive parameters copy to new drives as new machines progress through assembly.

Michael Grant
Yaskawa Electric America Inc.
New Berlin, Wis.

Ac drives from Yaskawa, New Berlin, Wis., helped resolve chronic dc drive and motor-service issues for a packaging-machinery manufacturer. Existing dc motors and drives on wrapping machinery provide low-speed torque for jogging plastic stock while pulling a vacuum on a conveyor. Problem was the motors and drives needed a lot of maintenance such as frequent drive adjustments for tracking and analog drift.

Switching to ac drives reduced setup time by 75%. Specifically, it took 30 to 45 min to tune the dc drive system. In comparison, it takes about 5 min to tune the ac drive and motor. Plus, ac motors can last two to three times as long as dc motors.

Dc systems typically need service or even replacement after 8,000 to 12,000 hr of operation. Also, these systems require a service technician making a trip to the user site to adjust pots and switches and tune the drive.

Horsepower ratings for the machine are 0.25 hp at 1.6 A and 200 Vac, 0.5 hp at 3.0 A and 200 Vac, and 2 hp at 8 A and 200 Vac. The 0.25 and 0.5-hp motors are in-feed motors. They jog and move the packaged product onto the vacuum belt, driven by the 2-hp motor. The vacuum motor operates under negative pressure and must handle the additional friction. This is critical at low conveyor speeds of less than 20 fpm. The motor also operates at low frequencies (1 to 5 Hz) and must produce the full 6 lb-ft of continuous torque.

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