All About Circuits Forum  

Go Back   All About Circuits Forum > Electronics Forums > The Projects Forum

Notices

The Projects Forum Working on an electronics project and would like some suggestions, help or critiques? If you would like to comment or assist others with their projects, this is the place to do it.

Reply   Post New Thread
 
Thread Tools Display Modes
  #21  
Old 04-17-2012, 03:50 PM
ocelot28374 ocelot28374 is offline
Junior Member
 
Join Date: Apr 2012
Location: Wyoming
Posts: 31
Default

Quote:
Originally Posted by shortbus View Post
A problem with a mechanical brake that may come up is, instead of burning out stator coils you will then start breaking blades. Using permanent magnet generators is a cheap solution but one with a problem with regulation. Because you can't easily regulate the out-put.

Not knowing what type of generator your using, either a radial or axial style, can you tell us? There is a way of regulating that isn't well known but seems to work pretty well called "field regulation". This is where you add a coil around the stator and put a current through it to counter act the current made in the stator. In effect it counter acts the fields of the rotating permanent magnets. Their using it in some PMDC motors for EVs to create 'field weakening' to get more speed from the motor at light load.
The generator uses a "Delco" style housing such as a traditional alternator.
Reply With Quote
  #22  
Old 04-17-2012, 03:54 PM
wayneh wayneh is offline
Senior Member
 
Join Date: Sep 2010
Location: Roscoe, IL
Posts: 7,613
Default

We're far into this thread but I don't feel like I have a grasp of what is needed. Let me reiterate some basic questions:

In high winds, the windmill will spin too quickly if allowed to spin free? Do we know anything about the rpm target? If the goal is to prevent over-rpm, then the braking control system should be based on rpm.

The windmill has built-in electronic braking (shunt load) but this is not robust and has overloaded? Do we know what failed, how and why? Might be easier to fix a flaw than do a re-design. How does the built-in system function? Maybe there is already a rpm detection?

The proposed redesign solution is to add on a mechanical brake (pads and disc?) to be operated by a electrical solenoid or similar? There is electrical power available from the turbine itself and/or from the charged batteries.

The missing information requested by the OP is the control circuitry to monitor the turbine and/or batteries, and somehow control the braking system?

Sorry if all this is obvious to others, but I've grown confused.
Reply With Quote
  #23  
Old 04-17-2012, 04:35 PM
ocelot28374 ocelot28374 is offline
Junior Member
 
Join Date: Apr 2012
Location: Wyoming
Posts: 31
Default

Quote:
Originally Posted by wayneh View Post
We're far into this thread but I don't feel like I have a grasp of what is needed. Let me reiterate some basic questions:

In high winds, the windmill will spin too quickly if allowed to spin free? Do we know anything about the rpm target? If the goal is to prevent over-rpm, then the braking control system should be based on rpm.

The windmill has built-in electronic braking (shunt load) but this is not robust and has overloaded? Do we know what failed, how and why? Might be easier to fix a flaw than do a re-design. How does the built-in system function? Maybe there is already a rpm detection?

The proposed redesign solution is to add on a mechanical brake (pads and disc?) to be operated by a electrical solenoid or similar? There is electrical power available from the turbine itself and/or from the charged batteries.

The missing information requested by the OP is the control circuitry to monitor the turbine and/or batteries, and somehow control the braking system?

Sorry if all this is obvious to others, but I've grown confused.
Wayneh, first battery state of charge is the condition that needs to be monitored. The physical speed of the turbine is controlled by the wind force itself effecting yaw. Which limits the output to a manageable current level. The wind generator is "rated" at 1600 watts by the manufacturer, to try and prevent burn up we have configured it to yaw at less than half of its proposed capacity. We have two of them. We also have another 1000 watts of solar generation capacity. The problem arises when the batteries have reached full charge and there is not enough load thru the inverter or other DC loads to consume the excess charge capacity. The diversion controller does a poor job of managing this, even with manufacturer support. We have burned up too many turbines and risk damaging the batteries. I am attempting to devise an alternate means of controling the turbine automatically without allowing excess current, and therefore heat, to distroy the turbine.

The problem with the control system ( shunt load ) is the coils of the stator itself. They do not have the wire size and insulation to sustain high current operation once the batteries have reached a full state of charge and the resistive load applies to much current drain for the batteries. If the shunt load was used without the batteries, ( shunt only to load not in parallel with the batteries ) the stator still can't handle the current it can create and burns up.

As for your understanding of what I would like help with.. You are not mistaken. I would like to use a voltage differential derived from the batteries desired state of charge level and the excess voltage level above desired state of charge to control a physical braking device. However I do not want to stop the turbine just slow it down.

I am sorry for any confusion. I am trying to answer the questions as thoroughly as possible.

Last edited by ocelot28374; 04-18-2012 at 12:58 AM.
Reply With Quote
  #24  
Old 04-17-2012, 04:55 PM
ocelot28374 ocelot28374 is offline
Junior Member
 
Join Date: Apr 2012
Location: Wyoming
Posts: 31
Default

Thank you to all who have viewed this thread and asked questions and posted suggestions.

With respect, I don't need help with the physical aspects of this. I need help designing a control "circuit" for it.
Reply With Quote
  #25  
Old 04-17-2012, 06:22 PM
Ron H's Avatar
Ron H Ron H is offline
E-book Developer
 
Join Date: Apr 2005
Location: Idaho, USA (GMT-7)
Posts: 7,050
Default

I apologize for making you repeat yourself, but please restate or point to the post describing what sort of electrical or electronic device you need to control in order to effect the braking. I got lost in the details.
Reply With Quote
  #26  
Old 04-17-2012, 10:43 PM
wayneh wayneh is offline
Senior Member
 
Join Date: Sep 2010
Location: Roscoe, IL
Posts: 7,613
Default

Quote:
Originally Posted by ocelot28374 View Post
The problem arises when the batteries have reached full charge and there is not enough load thru the inverter or other DC loads to consume the excess charge capacity. The diversion controller dies a poor job of managing this, even with manufacturer support. We have burned up too many turbines ...

The problem with the control system ( shunt load ) is the coils of the stator itself. They do not have the wire size and insulation to sustain high current operation once the batteries have reached a full state of charge and the resistive load applies to much current drain for the batteries. If the shunt load was used without the batteries, ( shunt only to load not in parallel with the batteries ) the stator still can't handle the current it can create and burns up.
Thanks for explaining this, but I remain confused. Not by your words. I don't understand why, other than poor design, you need to send power to the shunt and thereby overload the turbine leading to its premature death. This loading would make sense if it the load was being used to slow the turbine blades to protect them - electronic braking - but it sounds like you don't need that function because you have yaw control to protect the blades. I don't really see a need for the shunt load at all, or maybe it could be substantially reduced. Am I missing something?
Reply With Quote
  #27  
Old 04-17-2012, 11:44 PM
ocelot28374 ocelot28374 is offline
Junior Member
 
Join Date: Apr 2012
Location: Wyoming
Posts: 31
Default

Quote:
Originally Posted by Ron H View Post
I apologize for making you repeat yourself, but please restate or point to the post describing what sort of electrical or electronic device you need to control in order to effect the braking. I got lost in the details.
an electromagnetic coil sourced from an electric trailer brake system. each coil can sustain about 10 amps current I would like to use two to provide even loading on the rotor.
Reply With Quote
  #28  
Old 04-17-2012, 11:58 PM
ocelot28374 ocelot28374 is offline
Junior Member
 
Join Date: Apr 2012
Location: Wyoming
Posts: 31
Default

Quote:
Originally Posted by wayneh View Post
"you need to send power to the shunt and thereby overload the turbine leading to its premature death. This loading would make sense if it the load was being used to slow the turbine blades to protect them - electronic braking - but it sounds like you don't need that function because you have yaw control to protect the blades. I don't really see a need for the shunt load at all, or maybe it could be substantially reduced. Am I missing something?
To control the battery banks state of charge, with insufficient load on the batteries from inverters and such, the current produced by the generator would over charge the bank. In high wind conditions once the batteries have reached sufficient charge the turbine can "run away" and severely overcharge the bank. the shunt load does absorb this to a point but the wind has overwhelmed the controllers load and the turbines tolerance causing failure. I am just trying to come up with an alternative that wont allow the system to become overwhelmed by our sustained wind speeds. sometimes in excess of 80 mph for three or four days. more often over 40 mph. we have to leave the system unsupervised for up to two months at a time. an automatic limiting control that can not be "electrically" overwhelmed would be very helpful.

In theory I would like to eliminate the diversion load completely and have control over the system using speed control alone. Ideally this would be by variable pitch prop, but I can’t afford a system that complex and I do not have the machining skills required to build it myself.

Last edited by ocelot28374; 04-18-2012 at 12:15 AM.
Reply With Quote
  #29  
Old 04-18-2012, 12:45 AM
Ron H's Avatar
Ron H Ron H is offline
E-book Developer
 
Join Date: Apr 2005
Location: Idaho, USA (GMT-7)
Posts: 7,050
Default

Quote:
Originally Posted by ocelot28374 View Post
an electromagnetic coil sourced from an electric trailer brake system. each coil can sustain about 10 amps current I would like to use two to provide even loading on the rotor.
I think I had one of those left over from towing my Jeep behind my motorhome. It was a BF solenoid which pulled on the brake pedal. Sound familiar?
Do you want to PWM the voltage/current to modulate the force?
Reply With Quote
  #30  
Old 04-18-2012, 12:47 AM
CDRIVE's Avatar
CDRIVE CDRIVE is offline
Senior Member
 
Join Date: Jul 2008
Location: S. Florida USA
Posts: 2,223
Default

Quote:
Originally Posted by Ron H View Post
Do your blades have pitch control?
What's the name of that old 60s song? "You beat me to the punch..da da da".

Yes, this would be the ideal method.
__________________
__________________________________________________ ___________________________
Disclaimer: Any information that I post is intended for educational purposes only. No warranty or liability is expressed or implied. Note: Working with household line voltages (Mains) can be dangerous. Proceed at your own risk!
Reply With Quote
Reply   Post New Thread

Tags
, , , ,


Related Site Pages
Section Title
Textbook Tesla polyphase induction motors : Ac Motors
Worksheet Step-up, step-down, and isolation transformers
Textbook Stepper motors : Ac Motors
Textbook Synchronous Motors : Ac Motors
Worksheet DC motor control circuits
Worksheet DC generator theory
Textbook Automotive alternator : Ac Circuits


Similar Threads
Thread Thread Starter Forum Replies Last Post
Help! EMG Circuit Ocelot The Projects Forum 4 07-16-2011 03:18 PM
help me design an audio based camera controller circuit mehmehmeh The Projects Forum 8 03-21-2011 06:19 PM
555 timer circuit for servos MoC General Electronics Chat 4 03-18-2010 12:33 PM
wind turbine load control circuit polter The Projects Forum 4 02-26-2010 03:43 PM
Simple but big circuit Challenge to all Chris15 The Projects Forum 13 07-08-2009 09:32 PM

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT. The time now is 03:19 PM.


User-posted content, unless source quoted, is licensed under a Creative Commons Public Domain License.
Powered by vBulletin
Copyright ©2000 - 2014, vBulletin Solutions, Inc.