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Search: Posts Made By: DickDV
Forum: LIVE PLC Questions And Answers February 5th, 2019, 08:42 AM
Replies: 5
Views: 407
Posted By DickDV
Check for a 24VAC coil. It will overheat on DC...

Check for a 24VAC coil. It will overheat on DC power
Forum: LIVE PLC Questions And Answers January 16th, 2019, 08:33 PM
Replies: 12
Views: 531
Posted By DickDV
A transformer secondary with no point grounded...

A transformer secondary with no point grounded basically can float to any voltage AC or DC that the leakage will supply. I've measured 480VAC ungrounded delta floating at 1580VAC and, in another...
Forum: LIVE PLC Questions And Answers December 6th, 2018, 08:26 PM
Replies: 12
Views: 923
Posted By DickDV
To clarify, when I said phase-to-phase I meant...

To clarify, when I said phase-to-phase I meant from one coil to another. Clearly, that would only be meaningful if you can isolate the coils with the leads available in the junction box. Coils tied...
Forum: LIVE PLC Questions And Answers December 5th, 2018, 07:28 AM
Replies: 12
Views: 923
Posted By DickDV
lesmar. that is one million ohms phase to phase...

lesmar. that is one million ohms phase to phase or phase to ground. Of course, you can't test between coils that are internally connected.


These guidelines are for FIELD testing. There are other...
Forum: LIVE PLC Questions And Answers December 4th, 2018, 12:02 PM
Replies: 12
Views: 923
Posted By DickDV
Gentlemen, please consider that both ANSI and...

Gentlemen, please consider that both ANSI and NEMA spec 1000V meggars as proper for field testing of used induction motors. Also, consider that a brand new non-MG1 Motor is tested with 1200VAC at the...
Forum: LIVE PLC Questions And Answers October 29th, 2018, 08:26 PM
Replies: 8
Views: 514
Posted By DickDV
1000V megger is certainly a must. Also, if 460V...

1000V megger is certainly a must. Also, if 460V power is delta-sourced, you must either install a delta-wye drive isolation transformer or turn off the Ground Fault and Short Circuit Fault as they...
Forum: LIVE PLC Questions And Answers October 29th, 2018, 08:16 PM
Replies: 9
Views: 764
Posted By DickDV
Since wind/unwind applications are among the most...

Since wind/unwind applications are among the most difficult to implement and commission properly, I strongly recommend that you find a well-qualified systems group to do this job for you. I can tell...
Forum: LIVE PLC Questions And Answers October 29th, 2018, 08:07 PM
Replies: 21
Views: 1,304
Posted By DickDV
Probably the biggest reason Softstarters are...

Probably the biggest reason Softstarters are becoming a bit more common these days is the huge across-the-line inrush currents experienced with Premium Efficient Design A NEMA motors. A Code R motor...
Forum: LIVE PLC Questions And Answers August 18th, 2018, 06:48 PM
Replies: 17
Views: 1,265
Posted By DickDV
I agree that using the variator to avoid large...

I agree that using the variator to avoid large mechanical issues is probably wise if you can fix the ratio reliably. I would also set the variator ratio so the motor (assuming a 50hz motor) is at...
Forum: LIVE PLC Questions And Answers August 17th, 2018, 10:07 AM
Replies: 17
Views: 1,265
Posted By DickDV
To add a bit to jraef's good comments, choose a...

To add a bit to jraef's good comments, choose a new motor with the same hp as original but with more magnetic poles. For example, if original is 1800rpm motor (four poles), choose a 1200rpm motor (6...
Forum: LIVE PLC Questions And Answers July 21st, 2018, 03:13 PM
Replies: 8
Views: 1,125
Posted By DickDV
Companies making paper machine winders use a lot...

Companies making paper machine winders use a lot of air knives to do flying splices. You might find some expert help there
Forum: LIVE PLC Questions And Answers June 1st, 2018, 11:13 AM
Replies: 2
Views: 697
Posted By DickDV
I assume that 230VAC line to line single phase...

I assume that 230VAC line to line single phase means 230V split phase as in the supply transformer having a 230VAC secondary with the centertap grounded for the neutral.

If that is the case, then...
Forum: LIVE PLC Questions And Answers June 1st, 2018, 10:52 AM
Replies: 3
Views: 713
Posted By DickDV
One problem that can come up with bipolar speed...

One problem that can come up with bipolar speed and direction is that it is hard to get a true zero speed. The slightest offset voltage or even noise can cause the shaft to creep forward or backward....
Forum: LIVE PLC Questions And Answers May 23rd, 2018, 08:57 AM
Replies: 21
Views: 2,107
Posted By DickDV
One late thought on this. Since this is reported...

One late thought on this. Since this is reported to only occur when going from load to no-load, the problem may be caused by the speed loop being tuned up a little too hot. Reducing the P gain or the...
Forum: LIVE PLC Questions And Answers April 30th, 2018, 12:31 PM
Replies: 15
Views: 2,365
Posted By DickDV
jraef, can you give me a reference or two...

jraef, can you give me a reference or two concerning floating delta no longer being "code". That would be an answer to prayer and end a lot of me preaching against it if true.

That stuff almost...
Forum: LIVE PLC Questions And Answers April 30th, 2018, 11:54 AM
Replies: 5
Views: 753
Posted By DickDV
At 20 years old it would definitely be wish to...

At 20 years old it would definitely be wish to start budgeting for a replacement drive and even moreso considering it's Robicon. It's on short time for sure.
Forum: LIVE PLC Questions And Answers April 20th, 2018, 07:43 PM
Replies: 28
Views: 2,064
Posted By DickDV
to dmargineau, 1. Oversizing any brand or model...

to dmargineau,
1. Oversizing any brand or model of VFD is required on multiple motor applications not because of undersized output current specs but because multiple motors in parallel present such...
Forum: LIVE PLC Questions And Answers April 20th, 2018, 07:06 PM
Replies: 15
Views: 2,365
Posted By DickDV
Rather than buy input reactors, buy input 480/460...

Rather than buy input reactors, buy input 480/460 transformers with a 460/277 wye secondary. Arrange the output windings in wye (star) and ground the center of the wye.
You will have no more...
Forum: LIVE PLC Questions And Answers April 20th, 2018, 07:03 PM
Replies: 15
Views: 2,365
Posted By DickDV
Rather than buy input reactors, buy input 480/460...

Rather than buy input reactors, buy input 480/460 transformers with a 460/277 wye secondary. Arrange the output windings in wye (star) and ground the center of the wye.
You will have no more...
Forum: LIVE PLC Questions And Answers April 19th, 2018, 08:01 PM
Replies: 28
Views: 2,064
Posted By DickDV
I don't mean to offend any one but there has been...

I don't mean to offend any one but there has been a lot of nonsense mentioned here with respect to the ABB ACS355. I've used literally 100's of these units from fractional to 20hp and they are rock...
Forum: LIVE PLC Questions And Answers March 8th, 2018, 08:12 PM
Replies: 7
Views: 901
Posted By DickDV
In a perfect world, the DC braking current should...

In a perfect world, the DC braking current should stop flowing as soon as the motor stops spinning. As a practical matter, the timer is usually set maybe a second longer than actual brake time to...
Forum: LIVE PLC Questions And Answers March 8th, 2018, 07:58 PM
Replies: 1
Views: 705
Posted By DickDV
Actually three questions. All can be answered...

Actually three questions. All can be answered "yes". However, you are generally better off doing positioning with a servo. Trying to do it with a VFD is a stretch for the technology. Sure, various...
Forum: LIVE PLC Questions And Answers February 22nd, 2018, 06:46 PM
Replies: 10
Views: 644
Posted By DickDV
I'd vote for the RTD also. Much more accurate and...

I'd vote for the RTD also. Much more accurate and easy to calibrate.
Forum: LIVE PLC Questions And Answers February 22nd, 2018, 06:41 PM
Replies: 10
Views: 858
Posted By DickDV
Full support for jraef's comments on replacing...

Full support for jraef's comments on replacing the DC motor. I would suggest the ABB ACS800 drive as one of the best for serious Sensorless Flux Vector control as needed in this application. It will...
Forum: LIVE PLC Questions And Answers February 17th, 2018, 08:25 PM
Replies: 12
Views: 1,395
Posted By DickDV
I don't mean to suggest this as any kind of...

I don't mean to suggest this as any kind of practical solution but I believe you will find that an AC rated coil in a relay will operate successfully at a much lower DC voltage. You can play around...
Showing results 1 to 25 of 500

 
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