# Ford Ranger Electric Project(s)



## brian_ (Feb 7, 2017)

A couple notes about topics mentioned in the video...

*Induction motor efficiency* is not as bad as suggested. Look at a motor efficiency map for a Tesla Model S and it doesn't look much different from the permanent magnet synchronous motors. My guess is that you're thinking of the inefficiency of an industrial induction motor driven at constant (line) frequency starting from zero speed or being loaded too heavily and thus slipping excessively; an EV motor (or any motor properly run by a variable-frequency drive) never runs in that condition. Even at stall, the driving frequency adjusts to produce the optimal slip speed for maximum torque.

The Wikipedia note about *gearing *is not clear. I suspect that it was intended to suggest a 3:1 first reduction stage ("transmission") plus a second stage ("differential" or final drive, which would need to be about 4:1 to match your 12:1 observation), but this transaxle has the axles coaxial with the motor shaft and I have not seen the internal details. Obviously 3:1 overall is not right, and 12:1 is reasonable. If it is like the Chevrolet Bolt (and apparently the 2011-vintage Focus EV), a first stage pair of parallel gears drives a parallel shaft (which appears to be above and behind the motor and axle shafts), and the second stage from that shaft to the diff carrier uses a typical (for a transverse transaxle) driving gear and driven ring gear. If anyone has opened the case on one, they can just count teeth for the ratios.


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## Ladogaboy (Apr 25, 2010)

brian_ said:


> A couple notes about topics mentioned in the video...
> 
> *Induction motor efficiency* is not as bad as suggested. Look at a motor efficiency map for a Tesla Model S and it doesn't look much different from the permanent magnet synchronous motors. My guess is that you're thinking of the inefficiency of an industrial induction motor driven at constant (line) frequency starting from zero speed or being loaded too heavily and thus slipping excessively; an EV motor (or any motor properly run by a variable-frequency drive) never runs in that condition. Even at stall, the driving frequency adjusts to produce the optimal slip speed for maximum torque.


We'll have to disagree on that. The Tesla Model S is horribly inefficient. It saw a significant improvement by a second induction motor designed to operate a peak efficiencies under narrow circumstances when the motor was "put to sleep." The Model S then saw yet another, even more significant improvement in efficiency by dropping the second induction motor and replacing it with a PMAC motor. In head-to-head testing at 75 mph, it was more than 10% less efficient than the Bolt EV, which should never happen based solely on aerodynamics. The powertrain was just that much less efficient.

These induction motors in particular produce enough waste heat that they require a 16 liter per minute glycol cooling loop. Induction motors are for sure less efficient than PMAC.



brian_ said:


> The Wikipedia note about *gearing *is not clear. I suspect that it was intended to suggest a 3:1 first reduction stage ("transmission") plus a second stage ("differential" or final drive, which would need to be about 4:1 to match your 12:1 observation), but this transaxle has the axles coaxial with the motor shaft and I have not seen the internal details. Obviously 3:1 overall is not right, and 12:1 is reasonable. If it is like the Chevrolet Bolt (and apparently the 2011-vintage Focus EV), a first stage pair of parallel gears drives a parallel shaft (which appears to be above and behind the motor and axle shafts), and the second stage from that shaft to the diff carrier uses a typical (for a transverse transaxle) driving gear and driven ring gear. If anyone has opened the case on one, they can just count teeth for the ratios.


Yes, the Ford Ranger Electric doesn't have a true single reduction gear; it has a " two-stage direct reduction planetary gear system." The Bolt EV's reduction gear is technically a "parallel-helical reduction gear." From the end user's perspective, though, it shouldn't change things. The Ford Ranger Electric has a fixed gear reduction of 12.518:1.


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## brian_ (Feb 7, 2017)

Ladogaboy said:


> Yes, the Ford Ranger Electric doesn't have a true single reduction gear; it has a " two-stage direct reduction planetary gear system." The Bolt EV's reduction gear is technically a "parallel-helical reduction gear." From the end user's perspective, though, it shouldn't change things. The Ford Ranger Electric has a fixed gear reduction of 12.518:1.


Yes, the Bolt is a helical parallel gear train. The earlier Spark EV had a planetary reduction (the only easy way to build a single reduction stage coaxially), but it has just one stage to deliver its unusually small 3.7:1 reduction ratio; when GM went to a more typical reduction ratio requiring two stages, they got rid of the planetary design. 

Thanks for the Ranger info.  It's not surprising that the Ranger has two stages, given the desired reduction ratio, but it's surprising and interesting that they went with a planetary design.


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## brian_ (Feb 7, 2017)

Ladogaboy said:


> The Tesla Model S is horribly inefficient. ... In head-to-head testing at 75 mph, it was more than 10% less efficient than the Bolt EV...
> 
> These induction motors in particular produce enough waste heat that they require a 16 liter per minute glycol cooling loop. Induction motors are for sure less efficient than PMAC.


Okay, but in the video you were talking about huge cooling systems suggesting much greater loss - an automotive cooling system for an engine dissipates almost as much energy as goes into the output shaft.

The overall efficiency of the Tesla Model S isn't terrible - compare the energy consumption per distance travelled to other large EVs and (even after allowing for a Musk-style bias to the numbers) it's reasonably comparable.


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## Ladogaboy (Apr 25, 2010)

brian_ said:


> Okay, but in the video you were talking about huge cooling systems suggesting much greater loss - an automotive cooling system for an engine dissipates almost as much energy as goes into the output shaft.
> 
> The overall efficiency of the Tesla Model S isn't terrible - compare the energy consumption per distance travelled to other large EVs and (even after allowing for a Musk-style bias to the numbers) it's reasonably comparable.


Yes, everything is relative, I suppose. For similar power and size, a PMAC should be about 15% to 20% more efficient than an induction motor across the entire powerband. Unfortunately, we don't have a lot of good examples of EVs with a similar size to the Model S, and those we do have often make an apples-to-apples comparison impossible. I think the best proof of the efficiency advantage of PMAC motors is Tesla's own transition from induction to PMAC motors as a means of improving their vehicles' efficiency.


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## brian_ (Feb 7, 2017)

Ladogaboy said:


> I think the best proof of the efficiency advantage of PMAC motors is Tesla's own transition from induction to PMAC motors as a means of improving their vehicles' efficiency.


I agree with that. Tesla started with whatever was available cheaply, and has avoided significant changes to the Model S/X. With the Model 3 they switched to current technology.

Induction motors can still make sense in applications where they are spinning idle much of the time, such as in front drive units of mid-engine hybrids or AWD EVs in which the designer chooses to run only one motor normally. The Tesla Model 3 and Audi Q4 Sportback e-tron both have an induction motor in front and a PM motor in the rear; they presumably run as rear wheel drive until front drive is needed for traction or power.

In a bizarre twist, Tesla has updated the Model S/X front motor to PM, keeping the induction motor at the rear - they will presumably run as front-wheel-drive vehicles at low power.


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## Ladogaboy (Apr 25, 2010)

brian_ said:


> I agree with that. Tesla started with whatever was available cheaply, and has avoided significant changes to the Model S/X. With the Model 3 they switched to current technology.
> 
> Induction motors can still make sense in applications where they are spinning idle much of the time, such as in front drive units of mid-engine hybrids or AWD EVs in which the designer chooses to run only one motor normally. The Tesla Model 3 and Audi Q4 Sportback e-tron both have an induction motor in front and a PM motor in the rear; they presumably run as rear wheel drive until front drive is needed for traction or power.
> 
> In a bizarre twist, Tesla has updated the Model S/X front motor to PM, keeping the induction motor at the rear - they will presumably run as front-wheel-drive vehicles at low power.


Yes, I definitely think induction motors have their place, but as a base motor, I think they're not ideal. 

I think the only reason Tesla added an induction motor to the front of the Model 3 is because they had already created the base platform as a RWD with PMAC. Switching that up might have added too much cost and expense. For performance purposes, it seems to me that the induction motor makes the most sense in the rear. 

I should also be clear that I don't have any intention of switching out these Ford Ranger Electric's rear induction motors with PMAC, but I might consider adding a PMAC. The front assembly of the Ranger is actually based off a 4x4 frame and chassis, so it might be possible to install a front axle off a 4x4 Explorer/Ranger and link it to a small PMAC motor. Fitment and integration would be really difficult, though, so this might be something I work on far in the future (if it's worth doing at all).


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