1336 WITH A SINGLE PHASE OUTPUT ?????

[loweryd]

I have an Allen Bradley 15 H.P. 1336 VFD that I suspect has an intermittent single-phase fault on the output. This drive is on a vertical lift conveyor system. There are times when the drive will start to lift the conveyor (frequency indicating + on the HIM) then the motor reverses direction (frequency still showing + on the HIM) and the lift starts to fall accelerating as it goes. We get no fault indications on the drive and have to E- Stop the system to prevent a crash. HAS ANY ONE ELSE EXPERENCED ANY THING LIKE THIS WITH TYPE OF DRIVE?

 

[jbartos]

Question: What has been done to remedy the situation? It appears that this may be a challenging item for the Allen-Bradley tech support too.

 

[ozmosis]

Can I assume you have a mechanical brake on the system? If so, it is highly possible that when the brake is released the drive has not generated sufficient torque to hold the load. If you have different weights on the conveyor then this could be why it works sometimes and other times it goes 'backwards'.
I'm not too familiar with the 1336 but most good drives on the market have a facility to monitor torque (or current for some) and when it has reached a certain threshold it provides a signal output to release the mechanical brake.
Just a thought.
The 1336 will have phase to ground or short circuit protection so if you were to lose a phase it should show a fault code.

 

[loweryd]

I have been dragging the motor brake to simulate a load. (Releasing the brake at about 20 HZ). The drive accel time is set at 1.5 sec. Run frequency is set at 60 HZ. The motor appears to reverse direction about the time the brake releases. When I run the drive and release the brake off of the run signal (no load situation) there is no problem.

As for as preventing crashes we are installing an encoder on the output shaft to positively monitor direction. The encoder signal will go into the PLC controlling the system and E-Stop if we get a direction error.

 

[jbartos]

Suggestions:
1. Motor might be tested for its proper function.
2. Motor parameters should be adequate for the mechanical load.
3. VFD controls might be checked for proper functioning.