how much more voltage ability from advancing motor

[email protected] said:

If I took a series dc motor and advance it how much would I be able to increase the voltage without doing damage? Since the higher voltage decreases needed amp would that cause less heat production?

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It does not work like that!

Your controller gives the motor the voltage that it needs for the demanded current

So when stationary it may need 10 v to get the desired 600 amps
As soon as the motor is spinning it develops a back EMF - so it needs MORE voltage for the same current
Example
Stationary 600 amps - 10 v -
1000 rpm - 600 amps - 40 v
2000 rpm - 600 amps - 70 v
3000 rpm - 600 amps - 100 v
4000 rpm - 600 amps - 130 v

The Three terms - current/voltage and rpm are linked

Advancing the motor enables you to use more RPM - but it also drops the torque from a given current at low speeds

My motor is advanced by 8 degrees - that means that I lose nearly 20% of my torque
Or that I need to run about 20% more current to get the same torque - the opposite of the effect you wanted

Increased battery voltage does reduce battery current
Example - 150 volt battery
Stationary 600 amps - 10 v - - 150v - 40 amps
1000 rpm - 600 amps - 40 v-- 150v - 160 amps
2000 rpm - 600 amps - 70 v- - 150v - - 280 amps
3000 rpm - 600 amps - 100 v- 150v - 400 amps
4000 rpm - 600 amps - 130 v- 150v - 520 amps

Example - 300 volt battery
Stationary 600 amps - 10 v - - 300v - 20 amps
1000 rpm - 600 amps - 40 v-- 300v - 80 amps
2000 rpm - 600 amps - 70 v- - 300v - - 140 amps
3000 rpm - 600 amps - 100 v- 300v - 200 amps
4000 rpm - 600 amps - 130 v- 300v - 260 amps

[email protected] said:

So you're saying diesel don't loose power the higher the rpm?
...
Diesel is not ignited it combust from compression so how does that make power from higher rpm really work.

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Of course diesel fuel is ignited; "ignition" just means the initiation of combustion. The more generic name for diesel engines is compression-ignition engines, while gasoline engines are normally spark-ignition.

While high-speed ability of diesels is limited by the duration of combustion (since the fuel is burned as the fuel is injected, rather than rapidly as in a spark-ignition engine), this isn't an issue at normal automotive engine speeds. Many diesel engines are designed for low speeds; that doesn't mean that you cannot have a high-speed diesel engine, and the Audi R10 racing engine produced peak power at 5,000 rpm... more than twice the maximum speed of a big truck engine.

This illustrates the importance of understanding why things work as they do, not just observing a trend and thinking it is a fundamental limitation.

[email protected] said:

So why tf the they put so many more gears in the semis ?

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A heavy truck (such as a highway tractor with semi-trailer) weighs 20 to 60 tons loaded, and is driven by an engine only capable of a few hundred horsepower, and even that only at one specific peak engine speed. To make the most of the engine, many gear ratios are provided to keep the engine close to the optimal point.

[email protected] said:

And gasoline don't get much power behind it until you get to a higher rpm

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That's not true. The speed of the peak torque of an engine depends on the specific engine design, including intake and exhaust tuning and camshaft profile. The big difference between common diesel and gasoline engines in low-speed torque production is that all of the diesels are turbocharged, and few gasoline engines are. If you compare a modern turbodiesel and modern turbocharged direct-injection gasoline engine of the same displacement at the same speed and boost, the gasoline engine will produce comparable or higher torque... but most people compare turbodiesels to non-turbo gas engines, or huge (6.7 L) diesels in pickup trucks to much smaller turbocharged gasoline engines.

Power is just the product of torque and speed, so if two engines produce similar torque at low speeds but one of them can continue to work well at higher speeds, the higher-speed engine will produce more power... and yes, the extra power will be at the highest speed, even though the higher-speed engine may produce superior power at all speeds, even the low end.

This illustrates the importance of considering the application context of any technology, instead of jumping to conclusions about the fundamental technology.



While this may look like it is all about gasoline and diesel engines, it is really about understanding the characteristics of technical designs, such as DC and AC electric motors, rather than jumping to invalid conclusions based on incomplete knowledge of some specific applications.

[email protected] said:

Thank anyway I thouggt when they started electric motors was full torque and was all the way to top speed

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Regardless of type, electric motors are typically limited in torque by current, and limited to a fixed maximum current from zero speed to a significant part of the way up their speed range - that's the constant-torque region. At the other end of the scale, the current through the motor is limited by the available voltage at high speeds, as an increasing amount of voltage is required to overcome back-EMF at higher speeds. In-between, while the motor itself could be limited by current or voltage, in practice in EVs they are limited by the power that the battery or controller or cooling system can handle, so they are effectively constant-power (so decreasing torque with speed) over much of their speed range.

So

1. constant-torque (limited by current) from zero to some transition point,
2. constant-power (limited by battery, electronics, and cooling) from the transition point to nearly the maximum speed, and
3. decreasing power approaching top speed.

In a DIY system with a brushed DC motor, it may go straight from constant-torque to decreasing power, since it is so voltage-limited and control is so basic.

If the design of the system is messed up badly enough, it might be current-limited over the entire usable speed range - that would give you constant torque from a standstill to top speed, and indicates poor use of the capabilities of the battery and/or the motor.