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Monitor motors and drives for safety’s sake

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Bonfiglioli is engineering electronically monitored motor and gearbox combinations to make conveyor, crusher, feeder, pump and mixer operation safer.

The gearbox combinations incorporate VVVF frequency inverter technology to improve process control.

Their fine control and monitoring is useful for monitoring the driven or machine load on motors and drives, and reacts quickly when loads suddenly change, such as if a belt breaks or slips.

Bonfiglioli electronic automated division national manager Sean Richardson says instead of materials handling equipment breaking down or perhaps injuring someone, electronic monitoring can sound an alert or shutdown equipment automatically.

This load absence monitoring is now a common requirement in modern process control for safety and production issues. It needs a process control device to monitor the load side of its function, and to react to a lack of load in pre-determined ways.

“In the case of the latest VVVF drives, the process control device is the ACT inverter and the load is the electric motor,” Richardson says.

“When applied in Bonfiglioli’s proprietary V Belt Monitoring firmware, which comes standard with the ACT series, the technology constantly monitors the effective RMS output current of the VVVF drive.

“Because the current demand of the motor is directly proportional to the torque produced by the motor, the technology instantly recognises whether the load on the motor is either reduced or no longer there.

“For example, if something mechanical breaks in the power transmission, such as a gear or a chain, the torque demand on the motor is reduced, the motor current drops and the drive reacts.”

Richardson says this works simply. A percentage threshold is set based on the rated current of the drive. A time limit is set to monitor the low threshold. If the current falls below the set threshold for longer than the set time, the drive condition changes.

For example:

Drive rated current – 18A (7.5kW motor)

Adjustable % threshold – 20% (18A x 20% = 3.6A)

Adjustable time – 5 seconds

In this example, if the ACT400–018 only sees 3.6A on the motor for more than five seconds it reacts.

Process equipment can be programmed to react to such changes in different ways to improve safety.

“We can change the reaction of the drive to have it issue a warning, we can have it close one of the digital outputs to activate an alarm or a light or we can have the drive trip on a defined error.

“It is totally adjustable to the users’ requirements.”

Richardson says it is important when setting up such a system to take note of the no-load current draw on the motor to prevent false trips.

Bonfiglioli’s Vectron Active technology controls industrial electric motors up to 18.5kW. This complements its electronic automation drive equipment in styles and configurations up to 800kW, including integrated motor and inverters.

The modular set up of Vectron series’ hardware, combined with the company’s software control and functionality, achieves reproducible operational results in a wide range of machinery. They govern operations ranging from simple speed variations to dynamic and complex servo-style operations.

“These new mechatronics combinations tie together, in high performance and safety-oriented packages, the best solutions that can be engineered to the particular needs of individual customers and different industries.

“Rather than engineers having to compromise with traditional solutions that frequently involve trade-offs between the electronic, electrical and mechanical suppliers, the new combinations can be tailored to total solutions,” Richardson says.

For more info: (03) 9543 7667

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