Uaf Usman
5th October 2007, 08:53
A different approach, but wouldn't that be the most efficient way to charge batteries?
I was involved in designing a commercial 6KW wind turbine for my final year B.Eng project and came up with a proposal from a fellow colleague on the selection of the most efficient type of generator available for prototyping as well as commercial dispatch.
The proposal was to use a low voltage AC motor (from ABM Drives, Germany) and an EV (Electrical Vehicle) controller from Curtis, UK. You guys must be wondering what I am talking about, but yes; the initial pre-test results are very promising. Now two years later after the concept is better interpretable into wind application, I am now intending to pursue this on my own into a prototyping stage.
The ABM gearmotor is available with over 10 types and gearing ratios, so that you can choose the right type and ratio suitable for the rotor size you have. For my project, I intend to use ABM's 7.6KW motor with a 1:15 gearing with possibly a 6-7m rotor. The duty cycle is continuous.
Efficiency ratings:
The ABM four pole brushless Asynchronous motor is rated at 96% efficient as a motor (not sure when used as a generator).
Transmission:
The planetary gearing is rated at 93% efficient.
Controller:
Curtis Controller is considered in the EV industry as a super-efficient motor controller and here is the catch, it's """Regenerative"""! Meaning it could turn the AG AC induction motor into a generator, manually or if a pre-selected rpm or speed is crossed (going downhill), and you can also opt for the strength of that braking effect i.e. emergency brake.
The controller inverts the battery DC voltage and current into AC current and turns the AC motor (imagine the EV is asked to move), and in regenerative mode, the AC power from the motor is converted back into DC and feed into battery (manual barking or sliding downhill).
The functionality is award-winning and extremely precise, sensitive and efficient, more importantly, controllable.
Not sure how they are doing that using state of the art electrics and computerized controls, but in an EV applications, using the above combination significantly increases the 'battery mileage'. What I was told by the Curtis sales engineer that 'no matter the speed of the EV' (in our case the rotor), if it's higher or lower than that battery voltage, it would be stepped up or down to charge the 48V batteries as effectively as possible – typically 85% efficiency or over.
Cost:
The great thing about using the combination is that you get to use a very high tech product at a low cost (comparatively, $1600 for the gear motor and $800 for the Curtis controller), you also get all the required tachometer displays & controls, user selectable rpm, control features, RS232 port, highly refined motor, gearbox and controller.
We are now planning to develop a switch that is triggered by a wind signal i.e. availability of wind either by using an analogue limit switch or a digital PNP anemometer with a PIC controller.
All this switch would do is to switch ON the controller in "sliding mode" (the EV is sliding down a hill) and the controller turns (maintains) the motor at a pre-selected speed , lets say 70 rpm rotor speed, any rpm more than that would mean the controller switches into regenerative mode, and starts charging the batteries.
Now, the unique thing is that no matter if the wind increases to 40 m/s, the controller would clamp it's rpm to the pre-selected rpm. Sounds cool! Also, it would never stall or let the rotor turn below a –predefined low-speed, even it had to turn itself into a motor!
Also, if the wind drops down for a while, it would keep the rotor turning in motor mode until wind picks up again and rpm are realized to be rising by the controller – thereby switching it into regenerative again.
Furthermore, you have an option of emergency barking (EV needs to comes to '0' mph) and in wind case, rotor is completely stopped. I am sure its much more than dynamic braking (shorting 3 phases in PMA) as the braking effect is as strong as if we were using a hydraulic or mechanical brake!
The emergency braking could be activated by a combination of PNP type anemometer with a PIC controller, when the wind is say: 20 m/s. The same PIC controller would do the switching on/off part described earlier on.
The motor has also a built in 'normally closed' mechanical brake that prevents the EV from turning when the controller is switched off, acts like a strong hand-brake.
I am sure such an approach has never been discussed on this board and anyone having experience with Curtis or another EV regenerative controller would immediately be able to assess the applicability of such type of an EV controller to a wind turbine.
I would like to learn form the community as 'what they feel about this concept'? As I mentioned earlier that it was an academic assignment initially, and every thing sounds great on the paper, whether or not pursuing this concept to a test or a prototyping stage would be worth trying or not?
Thanks.
I was involved in designing a commercial 6KW wind turbine for my final year B.Eng project and came up with a proposal from a fellow colleague on the selection of the most efficient type of generator available for prototyping as well as commercial dispatch.
The proposal was to use a low voltage AC motor (from ABM Drives, Germany) and an EV (Electrical Vehicle) controller from Curtis, UK. You guys must be wondering what I am talking about, but yes; the initial pre-test results are very promising. Now two years later after the concept is better interpretable into wind application, I am now intending to pursue this on my own into a prototyping stage.
The ABM gearmotor is available with over 10 types and gearing ratios, so that you can choose the right type and ratio suitable for the rotor size you have. For my project, I intend to use ABM's 7.6KW motor with a 1:15 gearing with possibly a 6-7m rotor. The duty cycle is continuous.
Efficiency ratings:
The ABM four pole brushless Asynchronous motor is rated at 96% efficient as a motor (not sure when used as a generator).
Transmission:
The planetary gearing is rated at 93% efficient.
Controller:
Curtis Controller is considered in the EV industry as a super-efficient motor controller and here is the catch, it's """Regenerative"""! Meaning it could turn the AG AC induction motor into a generator, manually or if a pre-selected rpm or speed is crossed (going downhill), and you can also opt for the strength of that braking effect i.e. emergency brake.
The controller inverts the battery DC voltage and current into AC current and turns the AC motor (imagine the EV is asked to move), and in regenerative mode, the AC power from the motor is converted back into DC and feed into battery (manual barking or sliding downhill).
The functionality is award-winning and extremely precise, sensitive and efficient, more importantly, controllable.
Not sure how they are doing that using state of the art electrics and computerized controls, but in an EV applications, using the above combination significantly increases the 'battery mileage'. What I was told by the Curtis sales engineer that 'no matter the speed of the EV' (in our case the rotor), if it's higher or lower than that battery voltage, it would be stepped up or down to charge the 48V batteries as effectively as possible – typically 85% efficiency or over.
Cost:
The great thing about using the combination is that you get to use a very high tech product at a low cost (comparatively, $1600 for the gear motor and $800 for the Curtis controller), you also get all the required tachometer displays & controls, user selectable rpm, control features, RS232 port, highly refined motor, gearbox and controller.
We are now planning to develop a switch that is triggered by a wind signal i.e. availability of wind either by using an analogue limit switch or a digital PNP anemometer with a PIC controller.
All this switch would do is to switch ON the controller in "sliding mode" (the EV is sliding down a hill) and the controller turns (maintains) the motor at a pre-selected speed , lets say 70 rpm rotor speed, any rpm more than that would mean the controller switches into regenerative mode, and starts charging the batteries.
Now, the unique thing is that no matter if the wind increases to 40 m/s, the controller would clamp it's rpm to the pre-selected rpm. Sounds cool! Also, it would never stall or let the rotor turn below a –predefined low-speed, even it had to turn itself into a motor!
Also, if the wind drops down for a while, it would keep the rotor turning in motor mode until wind picks up again and rpm are realized to be rising by the controller – thereby switching it into regenerative again.
Furthermore, you have an option of emergency barking (EV needs to comes to '0' mph) and in wind case, rotor is completely stopped. I am sure its much more than dynamic braking (shorting 3 phases in PMA) as the braking effect is as strong as if we were using a hydraulic or mechanical brake!
The emergency braking could be activated by a combination of PNP type anemometer with a PIC controller, when the wind is say: 20 m/s. The same PIC controller would do the switching on/off part described earlier on.
The motor has also a built in 'normally closed' mechanical brake that prevents the EV from turning when the controller is switched off, acts like a strong hand-brake.
I am sure such an approach has never been discussed on this board and anyone having experience with Curtis or another EV regenerative controller would immediately be able to assess the applicability of such type of an EV controller to a wind turbine.
I would like to learn form the community as 'what they feel about this concept'? As I mentioned earlier that it was an academic assignment initially, and every thing sounds great on the paper, whether or not pursuing this concept to a test or a prototyping stage would be worth trying or not?
Thanks.