The frequency inverter allows operators or maintenance personnel to modify drive parameters, reset faults remotely, and troubleshoot from a remote location using fault logs, alarms and drive monitoring.
One of the greatest benefits of upgrading overhead cranes with VFD control systems is that they are suitable for any type of crane application.
Low-end systems designed for modular cranes come standard with 30-40 programmable control parameters. On cranes with single-speed or two-speed motors, the frequency converter can be programmed to provide smoother acceleration and deceleration, and it can also be programmed to add additional speed points. For example, on a two-speed motor with speeds of 40 fpm and 120 fpm, an additional control can be added to allow an intermediate speed of 80 fpm, or the speed can be slowed down further by adding a 10 fpm control.
In a high end VFD system there may be as many as 200-300 programmable control parameters dialed into the controls for bridges, trolleys, cranes and hooks. A VFD can provide performance similar to DC control, but with a single speed motor. The VFD allows programming of acceleration and deceleration similar to the feel of a soft start device. However, because the VFD controls the voltage and frequency sent to the motor, the risk of overheating in Class D, Class, E and F high-purpose process cranes is eliminated.
On a high speed crane system, the speed control can be programmed to run the bridge at 300 fpm and lift down the runway, and with the flip of a switch, reduce the speed to 50 in a controlled fashion as the bridge approaches fpm. End of runway or picking point.
1. Reduce brake wear
If you ask any maintenance manager in a high output production facility, the biggest benefit of a frequency converter is that it eliminates or greatly reduces brake wear. On cranes without a VFD, each time the button is released, a mechanical brake is activated to slow and stop the crane’s motion. This wears down the brakes over time, and in high-use crane systems the brakes may need to be replaced every few months, or even every few weeks due to mechanical wear.
With a VFD system, once the button controlling the forward or reverse motion is released, the VFD controls the deceleration of the crane and slows and stops the crane in a controlled manner. These days, the brake is primarily used as a parking brake to hold the crane in place when it is not moving. This greatly extends brake life and reduces costly equipment downtime.
2. Adjustable acceleration and deceleration time
The bridge and trolley stops and starts are more abrupt on crane systems that are not equipped with a VFD. Over time, these sudden movements can cause excessive stress and wear on:
Drivetrain – including couplings, keyways and gearboxes
Trolleys, end trucks and wheels
Runway beams and structural supports
Wire rope or chain to support the load
A VFD allows you to fine-tune how long it takes the bridge or trolley to reach the desired speed and how long it takes to decelerate to a complete stop – greatly reducing stress on crane components and helping to prevent loads from swaying.
3. Precise load positioning
With variable frequency drives, bridges, trolleys and cranes can be programmed in any way with a 40:1 speed ratio For delicate loads or loads that require very precise positioning, the operator can nudge along its path of travel in a very slow and controlled manner bridge or hook.
The operator can run the load down the runway at a higher speed, and as it approaches the end of the stroke, he can flip a switch that is programmed to decelerate the crane to a predetermined speed—say 10 percent of the top operating speed, For example – he adjusted the final positioning of the load.
4. Load limit
The drive system can be programmed to detect a lift overload condition – stopping upward lift motion if it detects that the hook load reaches or exceeds a predetermined load limit. These can replace load cells in most applications
Torque limiting is also used to prevent the crane from performing lifts that could overload the motor and cause mechanical fatigue.
5. Fault codes and diagnostics
Software and hardware are available for operators, maintenance/production personnel or even remote third parties to program, monitor and troubleshoot drive systems. One crane or several cranes can be set up for monitoring and diagnostics related to drive parameters and drive status.
If something goes wrong, an alert with diagnostic information can be sent to a remote technician, or even directly to the operator’s transmitter. In most cases, maintenance personnel can diagnose and reset faults without climbing scaffolding or taking rides. Elevator access to cranes If they do need to be up in the air to operate a crane, they at least know what the problem is and can use the correct tools and parts to make repairs or adjustments.
Additional diagnostic information that can be provided includes: number of drives, number of cycles and alerts for routine or preventative maintenance based on crane usage.
The frequency inverter allows operators or maintenance personnel to modify drive parameters, reset faults remotely, and troubleshoot from a remote location using fault logs, alarms and drive monitoring.
One of the greatest benefits of upgrading overhead cranes with VFD control systems is that they are suitable for any type of crane application.
Low-end systems designed for modular cranes come standard with 30-40 programmable control parameters. On cranes with single-speed or two-speed motors, the frequency converter can be programmed to provide smoother acceleration and deceleration, and it can also be programmed to add additional speed points. For example, on a two-speed motor with speeds of 40 fpm and 120 fpm, an additional control can be added to allow an intermediate speed of 80 fpm, or the speed can be slowed down further by adding a 10 fpm control.
In a high end VFD system there may be as many as 200-300 programmable control parameters dialed into the controls for bridges, trolleys, cranes and hooks. A VFD can provide performance similar to DC control, but with a single speed motor. The VFD allows programming of acceleration and deceleration similar to the feel of a soft start device. However, because the VFD controls the voltage and frequency sent to the motor, the risk of overheating in Class D, Class, E and F high-purpose process cranes is eliminated.
On a high speed crane system, the speed control can be programmed to run the bridge at 300 fpm and lift down the runway, and with the flip of a switch, reduce the speed to 50 in a controlled fashion as the bridge approaches fpm. End of runway or picking point.
1. Reduce brake wear
If you ask any maintenance manager in a high output production facility, the biggest benefit of a frequency converter is that it eliminates or greatly reduces brake wear. On cranes without a VFD, each time the button is released, a mechanical brake is activated to slow and stop the crane’s motion. This wears down the brakes over time, and in high-use crane systems the brakes may need to be replaced every few months, or even every few weeks due to mechanical wear.
With a VFD system, once the button controlling the forward or reverse motion is released, the VFD controls the deceleration of the crane and slows and stops the crane in a controlled manner. These days, the brake is primarily used as a parking brake to hold the crane in place when it is not moving. This greatly extends brake life and reduces costly equipment downtime.
2. Adjustable acceleration and deceleration time
The bridge and trolley stops and starts are more abrupt on crane systems that are not equipped with a VFD. Over time, these sudden movements can cause excessive stress and wear on:
Drivetrain – including couplings, keyways and gearboxes
Trolleys, end trucks and wheels
Runway beams and structural supports
Wire rope or chain to support the load
A VFD allows you to fine-tune how long it takes the bridge or trolley to reach the desired speed and how long it takes to decelerate to a complete stop – greatly reducing stress on crane components and helping to prevent loads from swaying.
3. Precise load positioning
With variable frequency drives, bridges, trolleys and cranes can be programmed in any way with a 40:1 speed ratio For delicate loads or loads that require very precise positioning, the operator can nudge along its path of travel in a very slow and controlled manner bridge or hook.
The operator can run the load down the runway at a higher speed, and as it approaches the end of the stroke, he can flip a switch that is programmed to decelerate the crane to a predetermined speed—say 10 percent of the top operating speed, For example – he adjusted the final positioning of the load.
4. Load limit
The drive system can be programmed to detect a lift overload condition – stopping upward lift motion if it detects that the hook load reaches or exceeds a predetermined load limit. These can replace load cells in most applications
Torque limiting is also used to prevent the crane from performing lifts that could overload the motor and cause mechanical fatigue.
5. Fault codes and diagnostics
Software and hardware are available for operators, maintenance/production personnel or even remote third parties to program, monitor and troubleshoot drive systems. One crane or several cranes can be set up for monitoring and diagnostics related to drive parameters and drive status.
If something goes wrong, an alert with diagnostic information can be sent to a remote technician, or even directly to the operator’s transmitter. In most cases, maintenance personnel can diagnose and reset faults without climbing scaffolding or taking rides. Elevator access to cranes If they do need to be up in the air to operate a crane, they at least know what the problem is and can use the correct tools and parts to make repairs or adjustments.
Additional diagnostic information that can be provided includes: number of drives, number of cycles and alerts for routine or preventative maintenance based on crane usage.
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