Hi,
I have to replace a burned out & obsolete VFD on a machine with another make & model. The VFD will be driving a pallet hoist. The hoist drive motor (5HP) couples to a right angle worm gear reducer. The reducer output shaft drives a pair of shafts via roller chains & sprockets. This pair of driven shafts has lifting bars attached that the pallets sit on. On the end of the worm shaft opposite of the drive motor there is an electrical/mechanical brake that is attached to the gearbox housing. This brake is supposed to stop the hoist from moving when there is no power applied to the brake coil. It is energized to release in other words. The brake coil is energized from a relay. The relay is controlled by the machines SLC500 controller. There is a relay output card in the SLC500 chassis for driving the VFD digital inputs. There is an analog in/out card in the chassis for getting the speed signal to the VFD. A shaft encoder is installed on the motor shaft in between the motor & gearbox. I can’t access the parameters in the old drive & there is no documentation of VFD parameters that I can find. I don’t have a brake resistor available in the cabinet although the VFD does have DC brake resistor contacts installed.
I have all the bits & pieces here to make the machine do what I want. I’m just stuck on making a decision about the timing of the brake coil & VFD stop command.
Here is my question: What stop mode should I use in the VFD?
The Choices are:
What do y’all think I should do?
BD
I have to replace a burned out & obsolete VFD on a machine with another make & model. The VFD will be driving a pallet hoist. The hoist drive motor (5HP) couples to a right angle worm gear reducer. The reducer output shaft drives a pair of shafts via roller chains & sprockets. This pair of driven shafts has lifting bars attached that the pallets sit on. On the end of the worm shaft opposite of the drive motor there is an electrical/mechanical brake that is attached to the gearbox housing. This brake is supposed to stop the hoist from moving when there is no power applied to the brake coil. It is energized to release in other words. The brake coil is energized from a relay. The relay is controlled by the machines SLC500 controller. There is a relay output card in the SLC500 chassis for driving the VFD digital inputs. There is an analog in/out card in the chassis for getting the speed signal to the VFD. A shaft encoder is installed on the motor shaft in between the motor & gearbox. I can’t access the parameters in the old drive & there is no documentation of VFD parameters that I can find. I don’t have a brake resistor available in the cabinet although the VFD does have DC brake resistor contacts installed.
I have all the bits & pieces here to make the machine do what I want. I’m just stuck on making a decision about the timing of the brake coil & VFD stop command.
Here is my question: What stop mode should I use in the VFD?
The Choices are:
- Coast
- Ramp
- Ramp to hold
- DC brake
- Release brake coil: wait 50 ms, then issue run command. ( about 800 rpm)
- Run the hoist up until the pallet height detector is satisfied
- Issue stop command ( ramp ½ second)
- When shaft encoder detects “zero speed” apply brake to hold the shaft.
What do y’all think I should do?
BD