Product category:
Industrial Drives/Controls
News Release from: Rockwell Automation | Subject: PowerFlex 700
Edited by the Engineeringtalk Editorial
Team on 13 March 2006
Torque control optimises hoisting
applications
Lifting and hoisting applications can be both simplified and optimised thanks to TorqProve, a new and unique torque control feature on the Allen-Bradley PowerFlex 700 range of AC drives.
Lifting and hoisting applications can be both simplified and optimised thanks to TorqProve, a new and unique torque control feature on the Allen-Bradley PowerFlex 700 range of AC drives from Rockwell Automation TorqProve offers both torque control and mechanical brake redundancy, providing users with more onboard functionality - simplifying applications and reducing installation times and costs
This article was originally published on Engineeringtalk on 14 Mar 2003 at 8.00am (UK)
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Embedded controller aids drive application
The new Allen-Bradley PowerFlex 700S AC drive offers improved system performance, enhances flexibility and optimises installation.
VSD uses vector control for demanding applications
The Allen-Bradley PowerFlex 700 with vector control is an easy-to-use variable speed drive that provides high-performance speed and torque regulation yet is only half the size of similar products.
TorqProve is a product of the PowerFlex 700's flux vector control (FVC) architecture, which provides excellent torque and speed regulation, in combination with fast update times of torque inputs, enabling the drive to cope with occurrences such as torque shocks.
It can be used for many kinds of lifting, hoisting or elevator-type applications and simplifies them by automatically co-ordinating the stopping and starting actions of the PowerFlex 700 drive with the setting and releasing actions of a mechanical brake.
This co-ordination is achieved by checking the current flow though all three motor phases.
Further reading
AC drives move up to higher powers
The popular Allen-Bradley PowerFlex 700 range of AC drives has been extended to 690V, making it ideal for high-power applications requiring precise, reliable and cost effective motor control.
Variable speed control for high-power applications
Rated from 132 to 250kW at 400 and 480V, the Allen-Bradley PowerFlex 700H AC drive meets OEM and end-user demands for precise, reliable and cost-effective motor control in high-power applications.
Only if enough torque is available to assume control of the load does it allow the mechanical brake to be released.
TorqProve works in conjunction with other integrated PowerFlex features.
One such feature, brake proving, is activated when the speed of the motor reaches zero.
The PowerFlex 700 sets the mechanical brake and then monitors motor movement to ensure the brakes ability to hold the load before releasing drive control.
If movement exceeds a set limit, an alarm is set and the drive will start a brake slip procedure.
This allows the motor to travel a set distance (brake alarm travel) before a second slip test is performed and this will be repeated continuously until the brake holds and the load stops slipping, or the load reaches the ground.
Control of the load is maintained at all times, ensuring that it descends to the ground in a controlled manner, should the mechanical brake fail.
In addition to brake proving, the PowerFlex 700 also offers: speed band limit, a function designed to ensure that, when a certain speed is commanded for the load, it actually travels at that speed; float, the condition when the drive is holding the load at zero speed without the need for the brake to engage; micro precision, which allows for slower, more precise (creep speed) operation; and, finally, fast stop, a feature that ensures ramp deceleration time is forced down to just 0.1s, and that the mechanical brake is applied immediately.
In applications not requiring the float or brake slip functions, the advanced features of PowerFlex 700 allow it to be used in encoder-less hoisting applications while still benefiting from the remaining TorqProve features.
The tight integration of torque control and mechanical brake control is just one example of how the advanced features of the PowerFlex range of AC drives from Rockwell Automation can simplify load management and provide cost-effective yet sophisticated motor control in a wide variety of applications.
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