Magnetek IMPULSE VG+ Series 3, Instruction Manual

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IMPULSE•VG+ Series 3 Instruction Manual – 07/25/05
6-12
Troubleshooting Encoder Related Faults
The faults in this section may involve the encoder feedback system. During system startup, these
faults are often caused by parameters that need to be adjusted. However, after the system has been
running for some time without a fault, this usually indicates a problem with the physical system and
adjusting the parameters should only be done after the physical system has been inspected.
Fault Code: Dev–1, Dev-2 Speed Deviation
Definition
Speed deviation faults mean that the drive output is not following the commanded speed reference.
This is possible if there is not enough torque available to follow the internal speed reference.
Therefore, speed deviations will typically occur when the drive is at its programmed torque limit. In
addition, if the drive receives erratic, or missing, encoder pulses, speed deviations are also possible.
If the initial drive tuning and start-up of the system was successfully completed and the crane has
been in operation without any faults, then the occurrence of this fault most likely indicates that
something mechanical with the system has changed or drive parameters were changed (i.e., failed
encoder, load snag, crane overload, change in acceleration or deceleration times, etc.).
Corrective Action
1. Do NOT continue to operate the hoist.
NOTE: Continued attempts to operate the hoist with speed deviation faults occurring can
result in loss of control of the load under certain circumstances.
2. As a precaution the load float time, parameter C8-10, should be set to zero until the source of the
speed deviation fault has been determined and corrected.
3. Verify if the load has snagged or if there is a load on the hook that exceeds capacity.
4. Check the alignment of the encoder pulse wheel with the sensor head, or the encoder shaft
coupling (depending on the type of encoder used). If the pulse wheel is misaligned or the shaft
coupling is loose the drive will get erratic pulse signals or no signals at all causing a speed
deviation fault or PGO (Pulse Generator Open) fault. Repairs to the encoder wheel or shaft
coupling should be made immediately before again attempting to operate the hoist.
5. If the encoder appears to have no mechanical problems, the encoder cable should be checked for
damage and replaced if a problem is found.
5.1 Each of the encoder wires should be checked for continuity.
5.2 The wires should be checked for shorts between any two wires.
5.3 The wires should be checked for shorts to the shield or ground.
5.4 Visually inspect the cable for damage that may be causing intermittent problems.
6. If the encoder feedback system checks out mechanically and electrically, then the last physical
check to make is for something in the mechanical system that might be resisting normal
operation. One example may be the brake is not opening fully and is causing enough drag to
prevent the system from operating at commanded speed.