Hybrid cars and regenerative charging of batteries

[RQ]

Can anyone explain how the sudden and large jolts of electrical power from
braking can be stored in a battery.
In order for meaningful amounts of energy to be converted to actually
stopping a heavy car the electrical jolt must be pretty big.
I have visions of boiling batteries and smoke wires, but of course that
doesn't happen so how does the system handle it.

rq

 

[AlanBown]

Can anyone explain how the sudden and large jolts of electrical power from
braking can be stored in a battery.
In order for meaningful amounts of energy to be converted to actually
stopping a heavy car the electrical jolt must be pretty big.
I have visions of boiling batteries and smoke wires, but of course that
doesn't happen so how does the system handle it.

rq

Dynamic breaking, or what I know it about does not produce large amounts of
current and voltage. The motor poles are reversed and the motor acts like a
generator. Since it requires power to drive a generator it is pretty
effective breaking. A small amount of generated power is put back into the
batteries. Sustained breaking, (minutes) might deliver a charge big enough
to boil the batteries. Not sure where you going to find a hill like that or
how your going to get the electric car up there.

 

[Uwe Hercksen]

Can anyone explain how the sudden and large jolts of electrical power from
braking can be stored in a battery.
In order for meaningful amounts of energy to be converted to actually
stopping a heavy car the electrical jolt must be pretty big.
I have visions of boiling batteries and smoke wires, but of course that
doesn't happen so how does the system handle it.

Hello,

a good brake is able to stop a car much faster than the motor would need
to accelerate to the same speed before braking. In other words, the
brake is able to consume much more power than the motor is able to generate.

But it is impossible to store the energy from an emergency braking back
to the battery, the battery and the electrical brake ( in fact, an
electrical generator ) should be too big, heavy and expensive.

An electrical and a mechanical brake must be combined, if you brake
soft, the energy can be stored in the battery, if you have to brake
hard, the mechanical brake is used and the energy is lost.

The trick is to avoid hard braking and to brake early and soft instead.
But if you can avoid braking, the energy conservation is even better.
Every loading and unloading of the battery is causing a loss of energy.

Bye

 

[Dwayne]

Can anyone explain how the sudden and large jolts of electrical power from
braking can be stored in a battery.
In order for meaningful amounts of energy to be converted to actually
stopping a heavy car the electrical jolt must be pretty big.
I have visions of boiling batteries and smoke wires, but of course that
doesn't happen so how does the system handle it.

rq

The electric motor(s) is(are) used as a generator(s). The forward momentum
of the vehicle powers the generator(s), and then in turn charge the battery.
Braking power is limited to the generating capacity, just like acceleration
is limited to motor power. In other words, you can use the regenerative
braking to slow down gradually. Also you can't accelerate from 0-60mph
instantaneously, therefore you cannot brake instantaneously. In order to
panic stop you will need friction brakes. If I recall correctly, the
theoretical efficiency of regenerative braking is 33%.

Dwayne

 

[SAMMMMM]

stop and consider, the braking can approximate the accelerating current.
that may also be controlled.
they usually use a pulse-width modulator and it controls the current when
it's
regenerating (charging) just like as when i's trying to accelerate the auto.
it does, however, take a bit more charging to restore an amount of power
when regenerating than it delivers when powering the auto.(discharging)
NIMH cells take about 1.5 times charging power for the amount of delivered
power.
sammmm

 

[John Gilmer]

The trick is to avoid hard braking and to brake early and soft instead.

I would bet that "dynamic braking" could give a subjective feeling of
'medium braking" if not "hard" braking.

 

[Uwe Hercksen]

panic stop you will need friction brakes. If I recall correctly, the
theoretical efficiency of regenerative braking is 33%.

Hello,

if we assume an efficiency of 75 % each for the electric motor, the
generator, the charged battery, the discharged battery, we get a total
efficiency from kinetic energy before braking back to kinetic energy
after acclerating again of 0.75*0.75*0.75*0.75 which is 0.31 or 31 %.
Very close to the 33 % you recalled.

Bye

 

[Roy Q.T.]

LISTEN: You guys are in a nightmarish cycle on breaking an electrical
vehicle.,

Somehow feeding it a back current or reversing the voltage is not a good
braking method even if the motor is designed for reversing.

what someone seems to recommend is like switching a standard motor into
reverse to slow it down or hard brake it., though the motor won't drop
off as a transmission would I seriously doubt that it is the best method
to brake an electric motor.#1 the strain is not something you'd be
comfortable in a vehicle. #2 there has to be an outside mechanical
influence on the drive system to brake the motor #3 precision braking of
en electrical motor using electrical or electronic signaling is probably
more of a dream than it is a reality for EV's. [yet possible]

you're better off just designing a power transfer/cut off to the motor &
diverting the transit power to the batteries recharge circuitry as
suggested, while employing conventional braking., if you want to get
fancy to boost your specs & prices; then fine, mess around with motors &
generators and see if you can build one that would screech to a halt on
a digital fed reverse voltage/power application, (consider variable ev
weight) would you need a clutch ? A State of the Art Clutch? I think it
would be too dynamic for current performance needs and it'd heat up &
consume too much of the sparse energy in the vehicle.The Energy being
the Issue.
Clutch/Transfer + Generated Power to Batteries ~ Dynamic Braking = all
power disconnect not too good., besides what good would an idle
generator do connected to a battery pack.

nevertheless a few seconds or minutes of generated power backfed into
your system is better than none, even if a minor consideration., one
could coast on a downhill strip and recharge };-) could be the
difference in a fun ride or pushing it to an outlet.

®oy

give me a few more years

 

[Dwayne]

LISTEN: You guys are in a nightmarish cycle on breaking an electrical
vehicle.,
Somehow feeding it a back current or reversing the voltage is not a good
braking method even if the motor is designed for reversing.

Regenerative braking does not involve an energy input from the batteries or
power supply. Rather it uses the forward momentum of the vehicle to
generate electricity from the electric motor(s). Regenerative braking is
well know and currently in use on some production electric & hybrid
vehicles.

"Know where all that braking energy goes when you stop in a normal car?
Nowhere, it's wasted. So when Toyota created the Prius, they came up with a
better idea.A regenerative braking system operates the electric motor as a
generator. So when you put your foot on the brakes, the kinetic energy is
converted into electrical energy and stored in the battery.The system is
particularly effective in recovering energy during city driving where
patterns of repeated acceleration and deceleration are common.What's the
point?
This system increases overall efficiency, and thus fuel economy."
http://www.toyota.com.au/Prius03/Portal/Article/0,1225,191-266-6223,00.html

Other Links (google regenerative braking):
http://www.hybridcarguide.com/regenerative-braking.html
http://www.insightcentral.net/encyclopedia/enregenerativebraking.html

Dwayne

 

[daestrom]

Can anyone explain how the sudden and large jolts of electrical power from
braking can be stored in a battery.
In order for meaningful amounts of energy to be converted to actually
stopping a heavy car the electrical jolt must be pretty big.
I have visions of boiling batteries and smoke wires, but of course that
doesn't happen so how does the system handle it.

There are several 'braking' methods with electrical motors. So far people
have responded with a mix of terms, not all of them correct. There are
three principle methods used to 'brake' a system driven by electric motors,
'dynamic braking', 'regenerative braking', and 'reversing or "plugging"'

'Dynamic braking' is the method of using the motor as a generator and
disipating the electrical energy produced in some form of dummy load such as
a resistor bank. When using DC machinery, this is very easy to do. The
armature is disconnected from the power supply and connected to a resistor
bank. The field current can be regulated to control the amount of braking
affect. This method of braking is widely used on diesel-electric railroad
locomotives. The resistor bank is a huge bank mounted inside the roof of
the engine compartment at the back end of the locomotive. Large
radiator-sized fans blow air across the resistor bank to disipate the heat.
Engineers use them when descending long grades rather than burn up the
friction brakes on the wheels.

'Regenerative braking' is very similar, except the electrical energy is not
just dumped to a dummy load. Rather, it is sent back to the power source.
Obviously, the type of power source has to be able to accept the energy.
Secondary cell batteries are one such source, but there are others.
Traction motor railway systems (electric trains) often use regenerative
braking and send the electrical energy back into the grid. Contrary to some
of the ideas posted, DC motors can be shifted from motoring to generating by
simply increasing the field current. No special contactors, or switching is
required, just set the field rheostat to maximum current and regenerative
braking will quickly slow the motor to minimum.

Both of these methods have the disadvantage that no braking force can be
developed until the motor is actually being spun by the load. Once the load
comes to rest, the braking force goes to zero (the motor/generator cannot
develop an electrical output at zero rpm).

'Reversing' (also sometimes known as 'plugging') is a method that can be
used to bring a spinning motor to a dead stop very quickly. This method is
to disconnect the normal supply and reverse the motor connections. Then
briefly reconnect the power supply. Often, the reconnection is controlled
by a small shaft-mounted switch that is driven by a drag-clutch. The moment
the motor speed drops below the switch's threshold or begins to reverse
direction, this 'plug switch' opens and causes the motor controller to
disconnect the power supply. This type of 'braking' can stop the motor
almost as fast as 'starting' can bring it up to speed. I think this is the
type that Roy QT was thinking of when he mentions special equipment
requirements. The current surge when 'plugging' is *higher* than the
starting current. Limitations on duty-cycle and power supply requirements
are usually needed. And even the shaft components can be a problem. I've
seen shaft keys sheared by in-advertant 'plugging'.

Most hybrid vehicles in the news these days use 'regenerative braking',
where the energy is put back into the battery system. Some manufacturers
try to make it sound like a 'major advancement'. But a 1000 kg car,
traveling about 26.8 m/s (about 60 mph) has a total kinetic energy of 359
kJoules of energy (K.E. = 1/2 m* v^2). Thats about 100 kWh. May sound like
a lot, but one gallon of gasoline has about 30480 kWh. So if regenerative
braking is perfect, for each stop from ~60 mph you reclaim the energy of
about 1/2 of a fluid ounce of gasoline (1 1/2 tablespoons).

Hardly seems worth it.

daestrom

 

[Don Kelly]

LISTEN: You guys are in a nightmarish cycle on breaking an electrical
vehicle.,

Somehow feeding it a back current or reversing the voltage is not a good
braking method even if the motor is designed for reversing.

what someone seems to recommend is like switching a standard motor into
reverse to slow it down or hard brake it., though the motor won't drop
off as a transmission would I seriously doubt that it is the best method
to brake an electric motor.#1 the strain is not something you'd be
comfortable in a vehicle. #2 there has to be an outside mechanical
influence on the drive system to brake the motor #3 precision braking of
en electrical motor using electrical or electronic signaling is probably
more of a dream than it is a reality for EV's. [yet possible]

you're better off just designing a power transfer/cut off to the motor &
diverting the transit power to the batteries recharge circuitry as
suggested, while employing conventional braking., if you want to get
fancy to boost your specs & prices; then fine, mess around with motors &
generators and see if you can build one that would screech to a halt on
a digital fed reverse voltage/power application, (consider variable ev
weight) would you need a clutch ? A State of the Art Clutch? I think it
would be too dynamic for current performance needs and it'd heat up &
consume too much of the sparse energy in the vehicle.The Energy being
the Issue.
Clutch/Transfer + Generated Power to Batteries ~ Dynamic Braking = all
power disconnect not too good., besides what good would an idle
generator do connected to a battery pack.

nevertheless a few seconds or minutes of generated power backfed into
your system is better than none, even if a minor consideration., one
could coast on a downhill strip and recharge };-) could be the
difference in a fun ride or pushing it to an outlet.

®oy

give me a few more years
---------

Regenerative braking is a tried and true method of braking - It has been
used succesfully in many applications. Motor switching or reversal is not
involved. When the motor generated voltage (so-called back emf) is greater
than the supply voltage, the current and energy flow reverse, not the
voltage so the motor acts as a generator. No separate generator is involved
and no mechanical switching is needed.
A hybrid car doesn't have a separate generator- the electric drive motor is
expected to do this, whether driven by the gasoline engine or by the wheels
on the road, and the control circuitry is designed for this.
However the main drawback of regenerative braking is that it cannot bring
the vehicle to a stop as its effectiveness decreases with speed.
Conventional braking is needed to actually stop or get effective braking at
low speed. . For most braking applications, i.e. reducing speed, say from 60
to 30, it is practical and beneficial.

 

[Roy Q.T.]

Re: Hybrid cars and regenerative charging of batteries

Group: alt.engineering.electrical Date: Thu, Apr 14, 2005, 4:34am
(EDT+4) From: [email protected] (Don Kelly)
LISTEN: You guys
are in a nightmarish cycle on breaking an electrical vehicle.,
Somehow feeding it a back current or reversing the voltage is not a good
braking method even if the motor is designed for reversing.
what someone seems to recommend is like switching a standard motor into
reverse to slow it down or hard brake it., though the motor won't drop
off as a transmission would I seriously doubt that it is the best method
to brake an electric motor.#1 the strain is not something you'd be
comfortable in a vehicle. #2 there has to be an outside mechanical
influence on the drive system to brake the motor #3 precision braking of
en electrical motor using electrical or electronic signaling is probably
more of a dream than it is a reality for EV's. [yet possible]
you're better off just designing a power transfer/cut off to the motor &
diverting the transit power to the batteries recharge circuitry as
suggested, while employing conventional braking., if you want to get
fancy to boost your specs & prices; then fine, mess around with motors &
generators and see if you can build one that would screech to a halt on
a digital fed reverse voltage/power application, (consider variable ev
weight) would you need a clutch ? A State of the Art Clutch? I think it
would be too dynamic for current performance needs and it'd heat up &
consume too much of the sparse energy in the vehicle.The Energy being
the Issue.
Clutch/Transfer + Generated Power to Batteries ~ Dynamic Braking = all
power disconnect not too good., besides what good would an idle
generator do connected to a battery pack.
nevertheless a few seconds or minutes of generated power backfed into
your system is better than none, even if a minor consideration., one
could coast on a downhill strip and recharge };-) could be the
difference in a fun ride or pushing it to an outlet.
®oy
give me a few more years
---------
Regenerative braking is a tried and true method of braking - It has been
used succesfully in many applications. Motor switching or reversal is
not involved. When the motor generated voltage (so-called back emf) is
greater than the supply voltage, the current and energy flow reverse,
not the voltage so the motor acts as a generator. No separate generator
is involved and no mechanical switching is needed.
A hybrid car doesn't have a separate generator- the electric drive motor
is expected to do this, whether driven by the gasoline engine or by the
wheels on the road, and the control circuitry is designed for this.
However the main drawback of regenerative braking is that it cannot
bring the vehicle to a stop as its effectiveness decreases with speed.
Conventional braking is needed to actually stop or get effective braking
at low speed. . For most braking applications, i.e. reducing speed, say
from 60 to 30, it is practical and beneficial.
-- Don Kelly --

Except for the part of the Motor/Generation ~>

[which needs to be made optimal by design, the nature of an electrical
motor in itself isn't cause for much plus on the energy of the batteries
to engine cycles]

~ it's just what i said.

maybe should have a seperate eff generator on the axles or somewhere,
like dynamos that could be engaged with a lever or switch., then a push
could get you a long way};-)
®oy

 

[RQ]

Many thanks for the various opinions on my original post concerning the
method used to store a relatively large electrical charge over a very short
time span into a bank of batteries. As an old retired power plant
operator who had to care for and maintain various battery packs to provide
cranking power for gensets etc and for various UPS applications for
instrumentation, computers, one of the cardinal sins of battery care was
overcharging and recharging at too high a rate. It was a real no no
because it was hard on the cells.

If you visit the WebPages of the car companies who are selling hybrids,
there is no shortage of information extolling the advantages of regenerative
braking and how the energy is recovered by going back into the battery pack.
No one makes a claim of 100% recovery and everyone notes that this works in
conjunction with normal brake systems.

In real world driving, there is probably a 4 to 8 second time period in
slowing down and stopping for a red light where the energy of a 3000 lb car
slowing from say 60k to 30k is converted to watts and stored in that 4 to 8
second time frame. That sounds like a hell of a jolt to me. Try imagining
cranking over a cold motor on a cold day for 20 seconds and then putting a
charger on to bring the battery back up to full charge in 20 seconds and you
will know what I mean. I still have some questions on the method, but I
guess the car manufacturers are keeping their cards close to their chests.





Rq

 

[Don Kelly]

Re: Hybrid cars and regenerative charging of batteries

Group: alt.engineering.electrical Date: Thu, Apr 14, 2005, 4:34am
(EDT+4) From: [email protected] (Don Kelly)
LISTEN: You guys
are in a nightmarish cycle on breaking an electrical vehicle.,
Somehow feeding it a back current or reversing the voltage is not a good
braking method even if the motor is designed for reversing.
what someone seems to recommend is like switching a standard motor into
reverse to slow it down or hard brake it., though the motor won't drop
off as a transmission would I seriously doubt that it is the best method
to brake an electric motor.#1 the strain is not something you'd be
comfortable in a vehicle. #2 there has to be an outside mechanical
influence on the drive system to brake the motor #3 precision braking of
en electrical motor using electrical or electronic signaling is probably
more of a dream than it is a reality for EV's. [yet possible]
you're better off just designing a power transfer/cut off to the motor &
diverting the transit power to the batteries recharge circuitry as
suggested, while employing conventional braking., if you want to get
fancy to boost your specs & prices; then fine, mess around with motors &
generators and see if you can build one that would screech to a halt on
a digital fed reverse voltage/power application, (consider variable ev
weight) would you need a clutch ? A State of the Art Clutch? I think it
would be too dynamic for current performance needs and it'd heat up &
consume too much of the sparse energy in the vehicle.The Energy being
the Issue.
Clutch/Transfer + Generated Power to Batteries ~ Dynamic Braking = all
power disconnect not too good., besides what good would an idle
generator do connected to a battery pack.
nevertheless a few seconds or minutes of generated power backfed into
your system is better than none, even if a minor consideration., one
could coast on a downhill strip and recharge };-) could be the
difference in a fun ride or pushing it to an outlet.
®oy
give me a few more years
---------
Regenerative braking is a tried and true method of braking - It has been
used succesfully in many applications. Motor switching or reversal is
not involved. When the motor generated voltage (so-called back emf) is
greater than the supply voltage, the current and energy flow reverse,
not the voltage so the motor acts as a generator. No separate generator
is involved and no mechanical switching is needed.
A hybrid car doesn't have a separate generator- the electric drive motor
is expected to do this, whether driven by the gasoline engine or by the
wheels on the road, and the control circuitry is designed for this.
However the main drawback of regenerative braking is that it cannot
bring the vehicle to a stop as its effectiveness decreases with speed.
Conventional braking is needed to actually stop or get effective braking
at low speed. . For most braking applications, i.e. reducing speed, say
from 60 to 30, it is practical and beneficial.
-- Don Kelly --

Except for the part of the Motor/Generation ~>

 

[Roy Q.T.]

Motors are what ! Just like Generators ?
then lets put a voltage across a generator and see how many rpms we get
from it.


Please Mr. Kelly you are standing too close to the Rift

®

 

[Tom Grayson]

There are several 'braking' methods with electrical motors. So far people
have responded with a mix of terms, not all of them correct. There are
three principle methods used to 'brake' a system driven by electric motors,
'dynamic braking', 'regenerative braking', and 'reversing or "plugging"'

'Dynamic braking' is the method of using the motor as a generator and
disipating the electrical energy produced in some form of dummy load such as
a resistor bank. When using DC machinery, this is very easy to do. The
armature is disconnected from the power supply and connected to a resistor
bank. The field current can be regulated to control the amount of braking
affect. This method of braking is widely used on diesel-electric railroad
locomotives. The resistor bank is a huge bank mounted inside the roof of
the engine compartment at the back end of the locomotive. Large
radiator-sized fans blow air across the resistor bank to disipate the heat.
Engineers use them when descending long grades rather than burn up the
friction brakes on the wheels.

'Regenerative braking' is very similar, except the electrical energy is not
just dumped to a dummy load. Rather, it is sent back to the power source.
Obviously, the type of power source has to be able to accept the energy.
Secondary cell batteries are one such source, but there are others.
Traction motor railway systems (electric trains) often use regenerative
braking and send the electrical energy back into the grid. Contrary to some
of the ideas posted, DC motors can be shifted from motoring to generating by
simply increasing the field current. No special contactors, or switching is
required, just set the field rheostat to maximum current and regenerative
braking will quickly slow the motor to minimum.

Both of these methods have the disadvantage that no braking force can be
developed until the motor is actually being spun by the load. Once the load
comes to rest, the braking force goes to zero (the motor/generator cannot
develop an electrical output at zero rpm).

'Reversing' (also sometimes known as 'plugging') is a method that can be
used to bring a spinning motor to a dead stop very quickly. This method is
to disconnect the normal supply and reverse the motor connections. Then
briefly reconnect the power supply. Often, the reconnection is controlled
by a small shaft-mounted switch that is driven by a drag-clutch. The moment
the motor speed drops below the switch's threshold or begins to reverse
direction, this 'plug switch' opens and causes the motor controller to
disconnect the power supply. This type of 'braking' can stop the motor
almost as fast as 'starting' can bring it up to speed. I think this is the
type that Roy QT was thinking of when he mentions special equipment
requirements. The current surge when 'plugging' is *higher* than the
starting current. Limitations on duty-cycle and power supply requirements
are usually needed. And even the shaft components can be a problem. I've
seen shaft keys sheared by in-advertant 'plugging'.

Most hybrid vehicles in the news these days use 'regenerative braking',
where the energy is put back into the battery system. Some manufacturers
try to make it sound like a 'major advancement'. But a 1000 kg car,
traveling about 26.8 m/s (about 60 mph) has a total kinetic energy of 359
kJoules of energy (K.E. = 1/2 m* v^2). Thats about 100 kWh. May sound like
a lot, but one gallon of gasoline has about 30480 kWh. So if regenerative
braking is perfect, for each stop from ~60 mph you reclaim the energy of
about 1/2 of a fluid ounce of gasoline (1 1/2 tablespoons).

Hardly seems worth it.

daestrom

Daestrom,
It seems that there are not a lot of posters here that have a good
understanding
of motor operation, specifically DC. It is good to see someone here, such as
yourself, that does.

I hope you do not mind if I add some general discussion to your comments.

There is a major difference between the Dynamic Braking and regenerative
braking.
With Dynamic Braking, when the energy is dissipated as heat, The Resistor
grids will continue to take load current as long as the motor is turning and
it has field. The slower the motor goes, the lower the voltage, and thus the
lower the current, and with it , Braking effort. As the motor slows,
braking effort can be maintained by increasing the field excitation, or
stepping out parts of the resistor, to get more current for the lower
voltage. (The machines we do use DC motors with Shunt fields)

If you wish to get Regenerative Braking into a battery, as you mentioned ,
all that has to happen is the motor field is to be increased so that the
motor counter EMF is higher then the battery voltage. Once this happens,
Current will drop to zero and then reverse. The reversal of Current will
produce a braking torque, which slows the Vehicle. The problem here is that
as the vehicle slows, the generated voltage for a given field strength will
drop linearly with speed. So as the Vehicle slows The only way to keep
regenerating current into the battery (which is basically a fixed voltage
source) is to keep increasing the motor field as the speed goes down.
There is obviously a speed where no amount of field current is going to give
you a voltage higher then your battery voltage, and braking effort will
cease.

Needless to say, the design of the Motor will have to be such that at normal
road speeds the
motor field will be quite a bit lower then it's maximum value, ( in the
field weakening region) and as the speed decreases, The field increase to
it's maximum value at base speed, After this some other way must be found to
stop the vehicle.

Because of this, Regenerating into a battery, using conventional thinking,
is not really a viable option.
I am not sure how the toyota people do this. maybe they have some sort of Dc
to DC converter to step the voltage up or perhaps they break the battery
bank into it smaller voltage cells and regenerate into these.
Either way they are adding in complexity and inefficiencies.

My Exposure to this application has been the Drives on the 240 Ton Mine Haul
Trucks.

Maybe someone else who is closer to the automotove application of DC Drives
can shed a little more light on the matter.

Have a good weekend, All
Tom

 

[daestrom]

Motors are what ! Just like Generators ?
then lets put a voltage across a generator and see how many rpms we get
from it.

If you knew a bit more about DC motors and generators, you would see that
Don is absolutely correct. Mechanically, and electrically, a shunt-wound DC
motor *IS* a shunt-wound DC generator. There is no difference at all,
except one you hook up to a DC power supply to turn a load, and the other
you hook up to a spinning shaft to generate electricity.

Old-style UPS systems used an AC induction motor to drive a synchronous AC
generator and a DC generator to charge batteries. Upon a loss of AC power
to the induction motor, the current in the DC machine would simply reverse
direction and draw power from the battery. The DC generator would instantly
become a DC motor, spinning in the same direction, just drawing power from
the battery instead of supplying power to the battery. The AC synchronous
generator output is used to supply the load at all times. It can't even
tell whether the shaft is being driven by the AC induction motor or the DC
machine acting as a motor.

If built with a substantial flywheel, these units can supply uninterruptable
power where voltage sine wave is hardly perturbed at all during the loss of
power to the AC induction motor.

Please Mr. Kelly you are standing too close to the Rift

Maybe you should learn there are more kinds of electrical machinery than the
blender you use to mix your drinks with. Although not very 'main stream',
DC machinery is quite flexible as a motor/generator.

daestrom

 

[daestrom]

Your conclusion is OK, but I think your car will have a KE of 100
watt-hours, not kilowatt-hours. Same on the energy content of gasoline.

At $.10 a kWh, (what I pay for electricity), your gallon of gas would be
worth $3048!

You are absolutely right!!! A single mistake (even in metric units) can
lead to bogus calculations. Should have spotted that myself. Ah well, "to
err is human". Some days I'm just more 'human' than others ;-)

daestrom

 

[Roy Q.T.]

daestrom:
Very tricky, those dc motors/generators.
thanks for the crash class on them., i'll keep it in mind.

®oy

 

[Roy Q.T.]

what i know about motors & generators is that the magnetic flux in
motors is induced mostly or all by electricity, with generators it is
imposed on the metallurgy or you'd get no excitement or hysterisis
curve.Not that they are all that harmonic, duhhh.....
you must think I'ma dolt......

®oy