Crane Jerk Problem during starting and stopping

[dondon_alba]

Dear All,

My apology for being quite and not returning back for a while, I extremely apologized and being thankful at the same time for everybody’s contribution.

The root cause of the problem is the broken “spider coupling” to one of the motor and a “damaged bearing” on one of the crane wheels. Electrically I increased the “S-curve” PAR 146 from 15 to 20, ACC time set to 12sec and DEC time set to 6sec. Motor control remained set at “Sensorless Vector”.

The crane is now working smoothly as before and very much happy.

Thanks,

Dondon

 

[dondon_alba]

Don - did you ever resolve this issue?

I have been struggling with almost the exact same issue in the same application - a multi-purpose bridge crane used for a carbon anode baking furnace.

PowerFlex700VC 125A drive drawing from a common DC bus supplying the bridge, trolley, and anode hoist drives. The bridge drive runs two 20hp Reliance RL-model bridge motors controlled by a ControlLogix PLC via ControlNet, all engineered by Rockwell and installed new. No encoder on either motor. The drive nor the individual motor overloads never trip. Been a problem every since the installation in 2007. Rockwell field engineers have been in four times to no avail.

The local Rockwell distributor has said he'd like us to go ahead and try another manufacturer's drive to see if that solves the problem. Say what???

Currently running in V/Hz mode, with the speed regulator just on the verge of being turned off - seems to be the best solution, but nowhere near acceptable. If I'm not ready when the operator takes off, the repetitive jerking occuring on about a 1/2-second frequency interval just about knocks me off my feet. The operators refer to this crane as the bucking bronco.

An identical sister crane has the A-B 1395 DC drives and another larger crane of similar function has the Reliance GV3000 AC drives - both ride like Cadillacs. The problem-child crane used to run well with its 1395 drives, until the conversion. Of course, the drives that have been proven to work well are now obsoleted.

The jerking seems to be the worst when taking off from a stop, trying to position at slow speeds. Wide-open throttle take-offs aren't too bad but not great either. Joystick verified for clean signal. Motor brakes verified for full release. Several parameters such as jerk rate, accel/decel rates, current limits, speed regulator gains and the like have been run from one extreme to the other to find a happy/happier medium. Once things are moving at, say, greater than 10-15Hz, it runs smooth. Decel is pretty good until just before zero speed.

The amperage trace on accel shows the fluxing current spike on start-up/energization, then what appears to be a upright half-wave rectified pattern starting out ranging from 0.5 minimum to 1.0 maximum of the drive FLA limit, then tapering off to a relatively steady current draw in 3-5 seconds.

Would appreciate any suggestions, as my magic hat is out of rabbits.

Hi wde3477,

If you are sure that no mechanical problems involved, please try to change the following parameters;

• PAR 53 – from V/HZ to Sensorless Vector
• PAR 146 – if set to 0, try to adjust gradually from 10 then work your way up to 20 after every testing until you feel some change in the crane oeration
• PAR 140 – Accel Time 1 – set it from 10 to 15 secs.
• PAR 142 – Decel Time 1 – set it a minimum of 6sec then adjust if required
• PAR 155 – set to 1 (RAMP)
• PAR 69 & PAR 70 set it 1.2
• PAR 449 – to start set it to 5 Rad/sec

Start by checking/changing these PAR and let us know the results.

Regards,

Don