crane regenerative power protection
- Thread starter catalin78
- Start date
elevmike
Member
You need to post more info.
ianplcnet
Member
www.keb.de Does AC drives and electronic regenerative units
ok
the crane haz dc motors : two coupled at rotating and other two big motors on lifting descending with some discrete converter old techonology.
simoregs are in 4q
i need some solution to protect crane power generators from reverse power wich simoregs and the discrete drivesc kick back in the sistem
the crane haz dc motors : two coupled at rotating and other two big motors on lifting descending with some discrete converter old techonology.
simoregs are in 4q
i need some solution to protect crane power generators from reverse power wich simoregs and the discrete drivesc kick back in the sistem
OK, ten years ago I worked a project that sounds similar. We had a huge resistor bank that the motors were connected to during re-generation. We were blowing SCR's in the drive because the timing was messed up on the contactor that put the power into the resistors instead of back into the diesel generator. Sorry, no schematics but your drive manufacturer should be able to work a solution.
ther resistor banks are there , there is some schematic with tree relays 1 current and two for voltage but i don't think they are working by the book , i saw some relays designed to check and signal reverse power , i am thinking on putting one of those to couple the resistor bank ...
PLucas
Member
catalin78
Before you go jumping in feet first and end up blowing up the drives or the generator, stop and think what you are doing.
What did the crane have on from new?
Have you changed the drives on this crane?
The fitting of a resistor bank to absorb the regenerative energy that the generator cannot handle is pretty standard, the resistors are designed to be switched online at a certain amount of KW regenerative power. The amount of resistance is also calculated, not guessed at.
It seems by what you have written so far, you have voltage and current sensing relays controlling when the resistors are switched online. I would confirm that these are working correctly. These relays probably control a rather large contactor, confirm that this is coming in when the relays are coming in. It might also be worth confirming the state of the contact tips on this contactor.
Has the generator got an electronic management system that displays what the generator is doing? If yes, does it state that the generator is over-volting when the drives are regenerating? Does the generator shut down to protect itself against this over voltage? If what I have stated above is what is happening, I would look at the resistor bank and the contactor and confirm that there is a complete circuit, as an open circuit resistor will cause the over volt problem on the generator. If you switch the resistors online at the wrong time you could end up dragging the generator speed right down, so I would be wary about making any changes to the control circuits unless told to do so by the crane/generator manufacturers.
I have attached a quick drawing of how I think the power side of the genny is set up, it might help explain what I said above.
Paul
Before you go jumping in feet first and end up blowing up the drives or the generator, stop and think what you are doing.
What did the crane have on from new?
Have you changed the drives on this crane?
The fitting of a resistor bank to absorb the regenerative energy that the generator cannot handle is pretty standard, the resistors are designed to be switched online at a certain amount of KW regenerative power. The amount of resistance is also calculated, not guessed at.
It seems by what you have written so far, you have voltage and current sensing relays controlling when the resistors are switched online. I would confirm that these are working correctly. These relays probably control a rather large contactor, confirm that this is coming in when the relays are coming in. It might also be worth confirming the state of the contact tips on this contactor.
Has the generator got an electronic management system that displays what the generator is doing? If yes, does it state that the generator is over-volting when the drives are regenerating? Does the generator shut down to protect itself against this over voltage? If what I have stated above is what is happening, I would look at the resistor bank and the contactor and confirm that there is a complete circuit, as an open circuit resistor will cause the over volt problem on the generator. If you switch the resistors online at the wrong time you could end up dragging the generator speed right down, so I would be wary about making any changes to the control circuits unless told to do so by the crane/generator manufacturers.
I have attached a quick drawing of how I think the power side of the genny is set up, it might help explain what I said above.
Paul
Plucas :some company put new drives for rotating arm , now two drives are working master- slave , the drives for lifting and descending are the same , but the solution for detecting the reverse power i don't think it's the same because as it's mounted doesn't detect reverse power , it's actually detecting an overvoltage with two threesholds on main tree phase power . Generators have protection for reverse power , the problem is that if i have only one generator running when the crane makes moves combinig with braking on descending mechanism the main stop switch wich is between generator an power line goes off , i will examine if reverse power protection of the generator can set it off or it goes off because of the overload .
The basic ideea here is that i thing the block wich detects reverse power in crane is not acting precisely and as a consequence the resistors don't go on when it should .
contactor for resistor is ok . it's checked . resistors too.
i wanted too see a schematic for this reverse power detection choosed on another crane or some sugestions about it
The basic ideea here is that i thing the block wich detects reverse power in crane is not acting precisely and as a consequence the resistors don't go on when it should .
contactor for resistor is ok . it's checked . resistors too.
i wanted too see a schematic for this reverse power detection choosed on another crane or some sugestions about it
PLucas
Member
catalin78
After reading yor last reply, I think I understand what you are now saying, well, the last line explains things to me...
Paul
After reading yor last reply, I think I understand what you are now saying, well, the last line explains things to me...
On our diesel cranes with regenerative DC drives, the control of switching the resistor banks online is done within the PLC, the current and voltage feedback from the drives themselves is fed into the PLC, the values from the drives are added together and scaled to give us the total KW that all the drives are pulling (or regenerating) and this figure is used to decided when to switch in the resistors, so I cannot offer you any schematic that may assist you.
Paul
elevmike
Member
Catalin78,
Is this a closed loop generator field control? Can you post prints for the current setup?
Is this a closed loop generator field control? Can you post prints for the current setup?
Plucas : Do you know the conditions to couple the resistors? i guess it's on descending , but if you read currents and power how can you know when you reached the maximum amount of reverse power ? i have plc but the drives for lifting/descendig mechanism are analog and i can't connect to it , only solution for what are you telling me is to change the other two drives .
elevmike :
the relay for current is used combined with two relays for voltage detection but they act on coupling the reverse power killer resistors .
their setup data is not to trust because a lot of people changed the settings , i saw on different manufacturers , some special relays for detecting reverse power they can read vectors and see exactly when i have reverse power , i was thinking to put one of these
elevmike :
the relay for current is used combined with two relays for voltage detection but they act on coupling the reverse power killer resistors .
their setup data is not to trust because a lot of people changed the settings , i saw on different manufacturers , some special relays for detecting reverse power they can read vectors and see exactly when i have reverse power , i was thinking to put one of these
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