Starter/generator?

[DeltaMike]

Although not universal, a generator does not make proper voltage until the higher RPM's have been reached. This is why aircraft use them on turbine engines. Generators are more suitable for the "Starter/Generator" combo what are known for weight savings on aircraft. Even so, generators are rarely seen on piston aircraft engines.



I'm a little suspect that a over-voltage/over-current circuit failed so spectacularly. Usually, it should cut out at 18v (or 29v depending on the system). Even the pre-solid state equipment (like carbon pile) was pretty reliable.

Yes, more specifically aircraft turbines idle typically at 50+% of max RPM and their generators would be online at those speeds after the starter mode is no longer needed.
Good question and a great forum to ask it.

 

[Mel]

I'm a little suspect that a over-voltage/over-current circuit failed so spectacularly. Usually, it should cut out at 18v (or 29v depending on the system). Even the pre-solid state equipment (like carbon pile) was pretty reliable.

Yep. It's rare, but it does happen.

 

[CrimsonEclipse]

Yep. It's rare, but it does happen.

Older system I'm guessing.
Had a old twin Cessna that had generators and a separate voltage regulator (under the pilot seat of all places).
Regulator went Tango Uni and over volted the system. The DC bus automatically isolated itself.
Got to watch the lights get extra bright for a split second.

Back then they had manually switched backup regulators.

What type of airplane had the problem?

 

[BSmith]

You are not misinformed (mostly).

Almost any automotive alternator made in the last 40 years needs rotor current in order to create any useful output. For those, a battery with at least some charge is required. There are exceptions. I've seen a couple alternators with enough residual magnetism on the pole pieces to spontaneously begin charging with no rotor current. These are few and far between (and usually old).

Another exception is a permanent magnet alternator, commonly found on motorcycles. As long as they're spinning they can create a useful output. That design is usually limited to lower current outputs. For example, the alternator on my KLR650 tops out at 17 amperes.

I have not seen anything with a an engine computer push-started with a dead battery. The ignition system simply won't function.

Public service announcement:
Never disconnect the battery while the engine is running. This creates a condition called a "load dump", which is a half-second long 70-80 volt pulse (in a 12V system) that will raise hell with the systems electronics.

Recently, I was looking for a cheap used car just to get me by until I get my Elio. In the classified adds, I found one I thought might fit the bill. When I went to test drive it, I found out that the battery had gone bad and the owner had taken it out so there was no batter in it. He proceeded to jump start it with another car and he disconnected it and it continued to run just fine (I was surprised since I didn't think you could do that). The car was way less than 40 years old but it continued to run so I could test drive it. If there were a voltage spike, it didn't seem to hurt anything and the engine continued to run fine while I drove it. Note: I didn't buy it.

 

[Ty]

Alternators both large and small can get the generating process started with the residual magnetism present in the rotor when it starts to spin. On a couple of occasions, we have had to do a procedure called "flashing the field" with AC generators (alternators) driven by truck sized diesel engines that had lost that residual magnetism, it involves very briefly connecting a 12 volt battery to the field connections.

One thing an alternator can't take is losing it's load (the battery) while running. I had this happen to one of our generators with a Deere 8.1 liter diesel. After the excitement had died down after the repairs were complete, we determined that the battery had had an internal cell connector open while the engine was running. The battery opening up caused the alternator to create a voltage spike that wiped out the diodes, the diode trio and the regulator inside the alternator. In addition, the spike wiped out the ECU of this electronically controlled diesel as well, so this turned into one very expensive repair.

I've disconnected the battery while vehicles were running many times to make a point... guess I've been lucky?

 

[Ty]

It doesn't really drop one component since they'd have to add the generator. It's trading the alternator for a generator. A design that hasn't been popular in the consumer automotive world for decades.

Doesn't sound like a good idea to have a design different from almost every other modern car rolling down the road.

Not so. Dump the regular alternator AND the starter. Run a toothed belt, put in an alternator/generator which can be used as a poor-man's start-stop system. Actually, there are manufacturers that do that already. You DO save one component, the starter but you complicate the alternator. However, you DO allow the vehicle to kill the motor and have the starter/generator keep things spinning for a while. I would think the engine would have to have some kind of clutch or slip gear in order for the belt to keep spinning without spinning the motor though.

 

[Ty]

Generation I BAS[edit]
General Motors introduced a mild hybrid system called belt alternator starter (or BAS) in the 2007 Saturn Vue Green Line. The BAS system is also used in the Chevrolet Malibu Hybrid and Saturn Aura Green Line. It operates similarly to other mild hybrids with a start-stop system, in that it shuts down the engine as the vehicle comes to a stop and instantly restarts it when the brake pedal is released.[1]

The BAS system is capable of providing modest levels of power assist during launch/acceleration and similarly modest levels of "blended" regenerative braking during deceleration. Although unable to operate in pure all-electric EV mode, the BAS system provides improvements to both city and highway fuel efficiency over similar non-hybrid versions. In more powerful eAssist versions, a BAS system can add power to prevent excessive gear changes under variable load. According to the EPA the 2009 Saturn Vue BAS hybrid garners an improvement of 32% city (19>25mpg) and 24% highway (26>32mpg) making the combined economy improvement 27% (22>28mpg) over the base 4cyl FWD version.[2] The system is reasonably simple and inexpensive, making BAS equipped vehicles some of the least expensive hybrids available.[3][4][5]

A 36 volt electrical system (operating at 42-45 Volts) is used to operate a permanent magnet motor/generator unit mounted to the engine in a similar fashion to a conventional alternator. Then through a high-tension drive belt, the BAS system is capable of starting or assisting the 2.4L Ecotec engine. A conventional 12V starter motor is retained and used whenever the engine is cold as during initial start-up. The air conditioning compressor continues to be operated through a belt-driven pulley, but for fuel economy improvement it can be disabled in auto-stop mode if the "ECO" A/C mode has been selected by the operator.

Vehicles with the BAS system use a conventional 4T45-E automatic transmission which has been modified to include a more efficient final-drive ratio and includes an electrically driven pump to provide pressure in auto-stop mode.

One perceived benefit of the BAS technology is that it fits in the same space as a conventional engine. No significant modifications were required to the vehicle chassis to accommodate the BAS system, with the 36V battery pack housed in the trunk or spare tire well. This allows the vehicles to be produced on the same assembly line as the non-hybrid versions, producing substantial cost savings and allowing the company to adjust production more easily.

Cobasys which supplies the BAS system's battery pack had to conduct a recall in 2008 apparently due to internal leakage of the battery modules.[6]

Citing supplier issues and slow sales GM has relegated the 2010 model year BAS hybrids (i.e. Malibu hybrid) to "fleet only" status.[7]

Generation II BAS (eAssist)[edit]
At the LA Auto Show, on November 15, 2010, General Motors announced that it would be releasing an all-new version of the BAS system available in the 2012 Buick LaCrosse.[8] While still a Belted Alternator Starter system, the system is named eAssist and includes a larger more powerful Hitachi-supplied[citation needed] 115 Volt Lithium Ion battery and a 15 kW (20 hp) motor-generator that delivers 79 lb·ft (107 N·m) of torque. The additional power provided by the more powerful battery and motor provides the ability to contribute more power, and more often able to electrically start and assist the 2.4L engine. The eAssist system also includes a specially modified GM 6T40 6-speed automatic FWD transaxle.[

Man, an Elio... excuse me... A the Elio with an additional 79 lb-ft of torque/20hp would be a kick... that would double it's take off from the line! (well, almost)

 

[electroken]

I've disconnected the battery while vehicles were running many times to make a point... guess I've been lucky?

Manufacturers of automotive electronics are supposed to test against ISO 7637-2, test pulse 5a, which is the "standard" load dump.

In reality, the magnitude of the pulse depends on how much current the alternator was sourcing at the time (more = bad) and how fast it was spinning at the time (faster = bad). Disconnecting a nearly charged battery at idle wont hurt much.

But why risk it?

 

[BilgeRat]

In the case of our generator engine, it was turning 1800 rpm, so I'd guess the alternator was turning about 4500 rpm. No wonder.

 

[DAVID BROWER]

In the effort to simplify, what are the obstacles to have a single unit do the starter and generator functions? I know most (probably all) cars have switched over to alternators and the starters tend to engage to start then dis-engage while the alternator tends to be driving by belt. However, if the design went back to a generator that would drop one component.

Just a thought....

ISETTAS & MESSERSCHMITTS HAD CRANK MOUNTED DYNASTARTERS IN THE 50's .

THESE USED CARBON BRUSHES THAT RUN AGAINST A SEGMENTED ARMATURE .
AS THE ARMATURE TURNS SEGMENTS ARE TURNED ON CREATING A MAGNETIC PULL
TO THE FIELD COILS AROUND IT .

ONCE THE MOTOR IS RUNNING , THE SAME DEVICE IS USED TO GENERATE ELECTRICITY .

IN THE MODERN DAY , THIS IDEA CAN BE DONE WITH PERMANENT MAGNETS MOUNTED IN THE FLYWHEEL AND
A CRANK SENSOR SO THE COMPUTER CAN ENERGIZE THE FIELD COILS IN SUCCESSION & TURN THE CRANK .

NO BRUSHES , EXTERNAL MOVING PARTS , BELT OR GEAR TEETH .
LIKE THE OLD DYNASTARTER , IT CAN BE USED TO GENERATE ELECTRICITY ONCE THE MOTOR IS RUNNING .