Off grid battery / lighting / lathe etc

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EV_dub
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Re: Off grid battery / lighting / lathe etc

Postby EV_dub » Sat Nov 12, 2011 8:45 pm

RobSmith wrote:Is there a better way of controlling the motor as a resistor is just a small electric fire and would be using electricity I could do without it using.
I shall just refresh my memory to remind myself what layout the armature and field windings are in.... I know one configuration allows it to rev to destruction.

Edit: Series wired with no load seems to be the route to destruction.
Edit 2: Looking at Wikipedia it seems it might be intended as series connected as it has a very low resistance field. I suppose it could be designed to work with a controller and seperately exited. I will ask in a more appropriate section.

Rob


If its only a series wound motor then the field is in series with the armature.

Other than using Pulse width Modulation to control speed which I think its like a fast switching system which in effect changes the average voltage sent to the motor. Thats a bit out of my depth though.

Your motor shouldnt race off load if you feed it with less voltage like 12v??
RobSmith wrote:.
Edit 2: Looking at Wikipedia it seems it might be intended as series connected as it has a very low resistance field. I suppose it could be designed to work with a controller and seperately exited. I will ask in a more appropriate section.

Rob


My guess LA and LB terminals are 1 pair = armature, LE and LF are the other pair =field. connect LB to LE, connect the positive of the battery to LF and connect the negative to LA. To make the motor go the other way connect LA to LE and the battery to LB.
1993 Veedub Golf, 156v, 1200A, 150ah's

RobSmith
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Re: Off grid battery / lighting / lathe etc

Postby RobSmith » Sat Nov 12, 2011 9:08 pm

EV_dub wrote:
RobSmith wrote:Is there a better way of controlling the motor as a resistor is just a small electric fire and would be using electricity I could do without it using.
I shall just refresh my memory to remind myself what layout the armature and field windings are in.... I know one configuration allows it to rev to destruction.

Edit: Series wired with no load seems to be the route to destruction.
Edit 2: Looking at Wikipedia it seems it might be intended as series connected as it has a very low resistance field. I suppose it could be designed to work with a controller and seperately exited. I will ask in a more appropriate section.

Rob


If its only a series wound motor then the field is in series with the armature.

Other than using Pulse width Modulation to control speed which I think its like a fast switching system which in effect changes the average voltage sent to the motor. Thats a bit out of my depth though.

Your motor shouldnt race off load if you feed it with less voltage like 12v??
RobSmith wrote:.
Edit 2: Looking at Wikipedia it seems it might be intended as series connected as it has a very low resistance field. I suppose it could be designed to work with a controller and seperately exited. I will ask in a more appropriate section.

Rob


My guess LA and LB terminals are 1 pair = armature, LE and LF are the other pair =field. connect LB to LE, connect the positive of the battery to LF and connect the negative to LA. To make the motor go the other way connect LA to LE and the battery to LB.


Yes, That is the way the terminals are wired. I could wire it like you say as a series setup and figure out how to create a variable voltage supply without huge losses.
PWM might be an option but I am not sure how that works in practice as the ons/offs are at full current so I am not sure if you might get a lot of brush wear from thousands of full current ons/offs.

I have not been able to find any info about it online. Another chap on DIY Electric car forum has the same motor and also cannot find any information about it.

Rob

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Re: Off grid battery / lighting / lathe etc

Postby RobSmith » Sat Nov 12, 2011 9:14 pm

Just thinking about it.. it would be better to have a variable voltage and not PWM.
The single phase motor currently on the lathe has a 50hz vibration which is noisy and the vibration has a detremental effect on the machined finish and accuracy. It shakes things too much.

Rob

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EV_dub
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Re: Off grid battery / lighting / lathe etc

Postby EV_dub » Sun Nov 13, 2011 10:36 am

RobSmith wrote: PWM might be an option but I am not sure how that works in practice as the ons/offs are at full current so I am not sure if you might get a lot of brush wear from thousands of full current ons/offs.

I have not been able to find any info about it online. Another chap on DIY Electric car forum has the same motor and also cannot find any information about it.

Rob


Current is only dependant on demand. The high current demand is only when getting up to speed or on heavy loads . Whilst the field strength builds up .

Just refreshed myself with my electrics notes:

Field control: a decrease in field curent will cause an increase in motor speed.
A small change in field strength causes a large change in armature current.
best used for normal running speed and upwards

Armature control: An increase in armature current causes an increase in speed
a decrease in armature current decreases speed
Usualy used for normal speed and downwards
1993 Veedub Golf, 156v, 1200A, 150ah's

RobSmith
Posts: 37
Joined: Sun Jul 25, 2010 9:32 pm

Re: Off grid battery / lighting / lathe etc

Postby RobSmith » Sun Nov 13, 2011 11:34 pm

EV_dub wrote:
RobSmith wrote: PWM might be an option but I am not sure how that works in practice as the ons/offs are at full current so I am not sure if you might get a lot of brush wear from thousands of full current ons/offs.

I have not been able to find any info about it online. Another chap on DIY Electric car forum has the same motor and also cannot find any information about it.

Rob


Current is only dependant on demand. The high current demand is only when getting up to speed or on heavy loads . Whilst the field strength builds up .

Just refreshed myself with my electrics notes:

Field control: a decrease in field curent will cause an increase in motor speed.
A small change in field strength causes a large change in armature current.
best used for normal running speed and upwards

Armature control: An increase in armature current causes an increase in speed
a decrease in armature current decreases speed
Usualy used for normal speed and downwards


Hi Dave,
I did not understand the 'Upwards' and 'Downwards' parts.
It is interesting the second note saying "A small change in field strength causes a large change in armature current."
I read that as it might be best to figure out how to control both field and armature as to get the best performance, lowest heat generation and least battery drain.
It sounds like you could get 'X' rotary output with infinite different field and armature currents and be either efficient or wildly inefficient.
Hmm
Interesting
Rob

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EV_dub
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Re: Off grid battery / lighting / lathe etc

Postby EV_dub » Mon Nov 14, 2011 8:39 am

[quote="RobSmith]
Hi Dave,
I did not understand the 'Upwards' and 'Downwards' parts.
Rob[/quote]

Upwards= increasing speed
downwards= reducing speed
1993 Veedub Golf, 156v, 1200A, 150ah's

RobSmith
Posts: 37
Joined: Sun Jul 25, 2010 9:32 pm

Re: Off grid battery / lighting / lathe etc

Postby RobSmith » Mon Nov 14, 2011 1:26 pm

EV_dub wrote:[quote="RobSmith]
Hi Dave,
I did not understand the 'Upwards' and 'Downwards' parts.
Rob[/quote]

Upwards= increasing speed
downwards= reducing speed[/quote]


Oh....
That is what I thought... but that just seemed too easy.
Rob

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Re: Off grid battery / lighting / lathe etc

Postby RobSmith » Sat Dec 03, 2011 9:44 pm

Hi All,
I just got back from picking up the 12 Trojan T1275 batteries from EV_Dub.

I will take them out the car tomorrow and get them in the shed.

I am wanting to get the best from them so want to determine what their current state is and then come up with a charging and maintainance routine.
We will be going off grid at some point but to start with, while we are in our current house, will use the grid to supply power for charging.

I am new to this so am trying to figure out what to do first.

Rob


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