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The Real! MUSTANG MACH E is here

Anything to do with the electric or hybrid world

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Belgian1979
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Re: The Real! MUSTANG MACH E is here

Post by Belgian1979 »

When you use VFD the curves look something like the ones on this page:

https://www.researchgate.net/figure/Tor ... _251869545
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Re: The Real! MUSTANG MACH E is here

Post by Belgian1979 »

Bear in mind I'm not designing electric cars for a living, so I can only speculate on what they do.

When reading up on the subject I note that the Tesla's seem to have a reduction gear to increase torque to the wheels. This obviously would reduce the top end speed substantially (I read somewhere that they use 9.34:1 reduction gear - not sure if correct though).

Anyway the only way that they can get enough top speed beyond the nominal rpm of the motor is to increase the frequency of the AC power. Beyond the nominal rpm point, they will not be able to still increase the voltage as it will have reached its maximum. What will happen is, they will drive the motor at say 200% or 300 % of the nominal frequency (50*200% = 100 Hz or 50 * 300 % = 150 Hz). Going over 100% is ok, but it has a drawback as you're magnitizing iron and the more frequency you use the higher the losses. (inductors impedance is frequency dependant). Since they cannot increase the voltage anymore, the torque is reduced even though speed can still increase (up to a point). At speeds higher than nominal obviously efficiency will decrease as a result.

As far as that Mustang is concerned I'm not sure if they have a reductor gear or not since they have 7 electric motors in place. The fact remains though that the amount of torque needed for a run like that requires a lot of current and the battery will be depleted very fast.
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Re: The Real! MUSTANG MACH E is here

Post by gruntguru »

The question of how quickly the battery depletes is actually very simple. Far easier to analyse using energy than current. All you need to know is the mechanical power required, the motor rpm and the conversion (motor, controller, inverter etc) efficiency at each stage. The energy draw at launch is actually fairly insignificant for two reasons:

1. Motor power output (= torque x speed) is zero at zero rpm.
2. The time spent at zero rpm once current starts flowing is also zero and the time spent getting the motor up to an efficient speed (with tyres spinning in the Mustang case) is very short.

Here is an example - only 416 hp and 12.3 sec 1/4 mile but the energy required for the quarter mile was only 1.1 kW.hr. Interestingly, more than half of that energy was recoverable if there was enough runoff for the Tesla to use regenerative braking. Total energy cost for the 1/4 mile? 6 cents.

https://www.dragtimes.com/blog/tesla-mo ... e-and-cost

The Mustang has 3.5 times the power but won't use 3.5 times the energy for two reasons:

1. The car is traction limited for the early part of the run and can't use full power for at least half the time (not distance).
2. The ET is less than for the Tesla, so energy (= power x time) will reduce.

On the other hand the Mustang wastes more energy in wheelspin than the Tesla.

I would estimate the Mustang energy at closer to 2 x the Tesla so about 2.5 kW.hr
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Re: The Real! MUSTANG MACH E is here

Post by gruntguru »

Belgian1979 wrote: Mon Oct 26, 2020 12:18 pm Bear in mind I'm not designing electric cars for a living, so I can only speculate on what they do.

When reading up on the subject I note that the Tesla's seem to have a reduction gear to increase torque to the wheels. This obviously would reduce the top end speed substantially (I read somewhere that they use 9.34:1 reduction gear - not sure if correct though).
Almost all (if not all) EV's use a reduction gear. To get high power from a compact lightweight motor, it must turn high rpm - much higher than the wheel rpm at Vmax.
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Re: The Real! MUSTANG MACH E is here

Post by Belgian1979 »

You've got your facts wrong as far as how those motors create torque and use current...good luck.
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Re: The Real! MUSTANG MACH E is here

Post by gruntguru »

Belgian1979 wrote: Tue Oct 27, 2020 1:39 pmYou've got your facts wrong as far as how those motors create torque and use current...good luck.
If you would like to quote any "facts" you disagree with, I can show you where you are wrong, otherwise your post belongs in the same category as this masterpiece.
Belgian1979 wrote: Sat Oct 17, 2020 1:54 pmElectric cars are nothing more than a piece of shit, a dumb idea.
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Re: The Real! MUSTANG MACH E is here

Post by Belgian1979 »

gruntguru wrote: Tue Oct 27, 2020 10:00 pm
Belgian1979 wrote: Tue Oct 27, 2020 1:39 pmYou've got your facts wrong as far as how those motors create torque and use current...good luck.
If you would like to quote any "facts" you disagree with, I can show you where you are wrong, otherwise your post belongs in the same category as this masterpiece.
Belgian1979 wrote: Sat Oct 17, 2020 1:54 pmElectric cars are nothing more than a piece of shit, a dumb idea.

Good for you, but the discussion is futile and I recommend you do follow a course on electric engineering before you even start an attempt at a discussion.
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