Application of precise stop function of Danfoss FC51 inverter

Customers often require industrial machinery and equipment, such as vertical packaging machines, canning machines, and small motor manufacturing equipment, to accurately stop the machine spindle at a specific position when powered down. Given the intense market competition, they also seek cost-effective solutions to achieve this precise stopping.

Danfoss FC51 series inverters offer a built-in precise parking function that meets these needs. With their exceptional braking performance and highly competitive pricing, they have emerged as an ideal choice for customers, delivering similar results to high-end inverters.

To illustrate, consider a recent precise stop function application implemented by Shanghai Xinling for a customer. The mechanical structure is depicted in Figure 1. 

Position detection sensors are installed at the upper and lower ends of the machine spindle, and the spindle motor reducer has a reduction ratio of 1:10. Assuming the motor is running at 62Hz, it takes approximately 333ms for the spindle to complete one revolution, based on an estimated motor speed of 1800rpm.

Here's how the precise stop function works:

Upon receiving a stop command, the controller detects the signal from sensor 1 and immediately adjusts the inverter's output frequency setting to 35Hz through communication. This causes the motor to decelerate from 62Hz to 35Hz within half a revolution, or 165ms.
When the controller receives the signal from sensor 2, it further reduces the motor speed to 7Hz in a similar manner. Thanks to the FC51 inverter's superior performance, these two deceleration processes are achieved smoothly and stably.
Upon receiving the signal from sensor 1 again, the controller promptly disconnects terminal 33 of the inverter, triggering its precise stop function logic. This action stops the spindle at a high speed, achieving exceptional repeat stop position accuracy.

Keep the factory default settings for other unrelated parameters. It should be noted that the precise stop inverse logic function of FC51 can only use terminal 33.