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Discussion Starter #1
I left this message awhile back,

"Great thread, packed with good stuff


...but, most of this info on contactors & precharging is kinda old

Are there any updates, new products, concepts or procedures?


Now, that there is a lot more use & data available,

Are electronic contactors (solenoids) "really" necessary if you have a good quality, properly rated & easily accessible manual emergency power cut-off?
(could probably even mount a momentary switch in the housing & a precharge resistor across the terminals)


I have heard this is sometimes done in electric motorcycle racing because;

...the electronic contactors consume energy, where the manual ones won't

...& they are just another electronic component, in the loop, to "potentially" fail


Is there a reason that the speed controller needs to be able to cut the main power to itself?"



I never heard any response, so I'll ask here:


What are the pros & cons of an electronic contactor over a mechanical contactor?

Has anyone designed a safe & reliable mechanical contactor?

Why does it have to be electronic?

..why not springs?

...or magnets?

...or both?


* I was thinking, kinda, like a mouse trap.

Hit a manual button or switch & BAM it snaps shut (or open in this situation) & breaks the connection


Still wondering

...so, I made one

It's "remedial" but, it's to experiment with & maybe help continue the conversation :D

https://www.youtube.com/watch?v=TK3EgOI77I0
 

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Discussion Starter #3
Hell you could mount a couple of these switches on the dash, you don't need that stinking electric stuff.
That's the spirit!

Ya, kinda like that

...but, a lot smaller

...& spring loaded (a big beefy spring)

...but, under the hood NOT inside the passenger compartment


Something a little more professional than just

...yanking on a cord attached to an Anderson connector in the trunk


Seriously,

a manual contactor/power disconnect

...would not rely on electronics

...& would not consume any precious energy

So, why is everyone still using electronic contactors?
('cause that's what the instruction book said?)
 

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OK, what's the DC voltage rating on your red button switch? Also, if you forget to switch the manual precharge on, there's a good chance a $500-$1000 controller gets blown. This is a case where relying on an automatic system, rather than your memory to flip a switch, is a much more reliable system. If you can, measure the steady state current through the precharge resistor on one of your EVs. It's very small.
 

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A Tyco / Givavac EV200 electronic contactor draws 130mA , neither here nor there for a 500 / 2000Amp switch!

Change your incandescant bulbs for LED & you will save that ten times over !!

You should also consider the losses involved in routing cabling to your big red button / manual disconnects. Less cable terminations , shorter cable runs is what you want.
 

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Discussion Starter #6
OK, what's the DC voltage rating on your red button switch? Also, if you forget to switch the manual precharge on, there's a good chance a $500-$1000 controller gets blown. This is a case where relying on an automatic system, rather than your memory to flip a switch, is a much more reliable system. If you can, measure the steady state current through the precharge resistor on one of your EVs. It's very small.
The "Big Red Button" switch with the precharge circuit that I assembled, is just a prototype, mainly for discussion & demonstration purposes

This one would be for smaller EV's like motorcycles, go karts, golf carts & buggies it is listed at;

...48VDC 150A continuous & 1,000A

http://www.longacreracing.com/products.aspx?itemid=1643&prodid=7594&pagetitle=Push-Pull+Battery+Disconnect+Switch+-+2+Terminal


I agree automated to a certain degree

...or at least designed well


My original design/plan was for a key switch & a micro switch (not just a rocker switch)

...they were to provide (2) functions

...lock the "Big Red Button" in the off (or open) position

...activate the precharge circuit (momentary micro switch)


Here is how it would work (in my head)

...the precharge circuit would be automatically engaged (momentarily) when the operator turned the key switch to unlock the power disconnect.

...this should precharge the circuit before the main power is connected & then be inactive (not connected) the rest of the time
 

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Why don't you draw a schematic of your design. The thing is, you don't ever want pack voltage directly connected to a ~motorcycle or larger controller with drained capacitors. Say a connector on a battery or somewhere in the HV system comes loose and you forget to turn off the manual switch before you reconnect it. KA-BOOM. A main contactor could(should) be programmed to drop out and be required to be turned back on when this happens. Here the fixed precharge resistor would automatically charge the caps before contactor is turned on. Your manual system may also not allow time for the caps to charge up. Check the current flow rate into the controller when the precharge resistor is turned on.

As far as using an underrated switch to control the HV system, here's what happened when one was used in a Zap Xebra: The owner tried to add an 12V boost(to 84V) battery to the existing 72V system, but tried to used a 32VDC rated marine battery isolator switch to control it. Something got crossed or reversed, the batteries started hissing and the wiring started smoking. When the owner flipped the switch to try to turn it off, the current just arch over in the switch and the resulting fire gutted the vehicle's interior as you can see.
 

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Discussion Starter #8
Why don't you draw a schematic of your design. The thing is, you don't ever want pack voltage directly connected to a ~motorcycle or larger controller with drained capacitors. Say a connector on a battery or somewhere in the HV system comes loose and you forget to turn off the manual switch before you reconnect it. KA-BOOM. A main contactor could(should) be programmed to drop out and be required to be turned back on when this happens. Here the fixed precharge resistor would automatically charge the caps before contactor is turned on. Your manual system may also not allow time for the caps to charge up. Check the current flow rate into the controller when the precharge resistor is turned on.

As far as using an underrated switch to control the HV system, here's what happened when one was used in a Zap Xebra: The owner tried to add an 12V boost(to 84V) battery to the existing 72V system, but tried to used a 32VDC rated marine battery isolator switch to control it. Something got crossed or reversed, the batteries started hissing and the wiring started smoking. When the owner flipped the switch to try to turn it off, the current just arch over in the switch and the resulting fire gutted the vehicle's interior as you can see.

Thanks for your replies & helping me learn, more, about this stuff.

"The thing is, you don't ever want pack voltage directly connected to a ~motorcycle or larger controller with drained capacitors."

...isn't this what the precharge is for? (so that does not happen)


As I said, the "remedial prototype" I assembled was to help demonstrate the concept of combining the (2) components together (main power disconnect & an electronic solenoid)

A couple of the goals were to have a light weight, manually operated, combined unit that could protect the system but,

...not be "power dependent" to operate (if your contactor fails, you have plenty of power available but, your still stuck)

...or a power consumer, like an electronic contactor (every little bit adds up)


Combining units = less cables

Not using an electronic solenoid (with it's heavy coil) = less weight

Put them together & your stats start climbing (economy, distance)


I agree, it needs more (a lot more R & D)

...maybe, like a timed relay in the precharge circuit (when activated, it keeps the connection closed longer) (for a "fuller" precharge)
(like, a "wait" light on diesel's)

or

...maybe, it can be set up, so that enough current is sent to the controller to

...precharge it's capacitators

...& so, it can "run" thru its prechecks (no high throttle signal etc.)

Then it could provide the "green light" so the operator knows it's "safe" to contact the full pack voltage to the controller



"Something got crossed or reversed, the batteries started hissing and the wiring started smoking. When the owner flipped the switch to try to turn it off, the current just arch over in the switch and the resulting fire gutted the vehicle's interior as you can see."

Why would the fuse NOT blow out & stop this?


*Using an underrated switch or fuse or wiring or anything, (on anything, really), is looking for trouble

I have learned that the term "functioning within specified parameters" (Data's android answer when someone asked how he was doing today?) is like the rule when working with E
 

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Discussion Starter #10
I know, there is "important" information the operator needs to know before it's "safe" to proceed & connect the "full" power/amperage of the battery pack to the speed controller & motor

...is the system precharged enough?

...has the speed controller gone thru it's diagnostic prechecks for any "fault" signals?
(over voltage, low voltage, high throttle signal detected etc.)


How do we find these things out?


Let's "think it thru"


I will use, how the system is currently set up on "El Moto" my electric motorcycle, as an example (see diagram (A) below)


Start at the battery, positive (+) terminal (bottom right)
(follow the red line)

...the "power" (pack voltage) goes into the main fuse (500A)

...the "power" comes out of the fuse then, goes thru a cable into the main power disconnect

...the "power" (when, manually switched on by the operator) comes out of the main power disconnect & goes thru a cable into the contactor

...the "power" (when switched "on" by the speed controller) then, goes thru a cable to the speed controller (B+) connection & also, thru another cable to the motor (+) connection

...the motor negative (-) goes thru a cable to (M-) on the speed controller (this is how the controller controls the motor, by applying or not applying the negative (-) to the motor)

...to complete the circuit, battery negative (B-) comes out of the speed controller & goes thru a cable back to the negative (-) terminal of the battery

...that, pretty much, covers the "main drive" power circuit (as shown in the diagram)


Now, lets look at the "small power" circuit


The "small power" starts at the output side of the main power disconnect, this way when the manual power disconnect is switched off, ALL POWER is disconnected
(follow the orange line)

...the "power" (still pack voltage) comes out of the main power disconnect then, goes thru a small wire (~16g.) into a fuse (5A)

...the "small power" comes out of the fuse then, goes thru a wire into an on/off switch

...the "small power" comes out of the on/off switch (when manually switched on by the operator) & goes thru a wire to the positive (+) (coil/switch) side of the contactor & also, thru a wire to the power (J-2 #1) pin on the speed controller (this switches it on & off)


To complete this circuit, the negative (-) comes out of the contactor (coil/switch) & goes thru a wire to the Main RLY (J1 #3) on the speed controller (this is how the controller controls the contactor)

* I think this is also how the speed controller shuts off &/or opens the circuit or "kills" the power going to the motor when it detects any "fault" signals
 

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Hi

When I first put my car on the road I did use a big old disconnect off a forklift

It had a lever you pulled to disconnect the battery - which I tied to an old spade handle in the cab

If you zoom in on the drivers side of my battery compartment you can see it

One piece was bolted to the bulkhead - the other moved away when you pulled on the "Oh Shit" handle
 

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Discussion Starter #12
Hi

When I first put my car on the road I did use a big old disconnect off a forklift

It had a lever you pulled to disconnect the battery - which I tied to an old spade handle in the cab

If you zoom in on the drivers side of my battery compartment you can see it

One piece was bolted to the bulkhead - the other moved away when you pulled on the "Oh Shit" handle

Very Kool, I like seeing the different ways that things are done

Primitive but, effective

...was that was your daily power cut-off?

...or just an "Emergency" power disconnect?
 

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Discussion Starter #13
Now, lets take a look at how it could work (in my head anyways)

Looking at diagram (B)

Start at the battery, positive (+) terminal (bottom right)
(follow the red line)

...the "power" (pack voltage) goes into the main fuse (500A)

...the "power" comes out of the fuse then, goes thru a cable into a manual power disconnect

...the "power" (when, manually switched on by the operator) comes out of the manual power disconnect & goes thru a cable to the speed controller (B+) & also to the motor (+) connection

...the motor negative (-) goes thru a cable to (M-) on the speed controller (this is how the controller controls the motor, by applying or not applying the negative (-) to the motor)

...to complete the circuit, battery negative (B-) comes out of the speed controller & goes thru a cable back to the negative (-) terminal of the battery


...that's the "main drive" circuit (as shown in the diagram)


Now, lets look at the "small power" circuit


On this set up, the "small power" starts at the input side (inside) of the manual power disconnect switch (follow the small red line)

...the "power" (still pack voltage) goes into a fuse (5A)

...the "small power" comes out of the fuse then, goes thru a wire (~16g.) into (3) on/off switches


When manually switched on by the operator

..."small power" comes out of the (#1) switch, goes thru a wire to the power pin (J-2 #1) on the speed controller (this switches it on & off) (follow the orange line)

..."small power" comes out of the (#2) switch, goes thru a wire & a resistor to a green "go" LED light on the dash board (follow the purple line)

..."small power" also, comes out of the (#3) switch, goes thru a precharge resistor to the "main power" cable to provide the precharge function (follow the green line)


To complete this circuit, the negative (-) coming out of the Main RLY (J1 #3) on the speed controller & connects to the "go" LED on the dash board


This way if/when the controller detects a "fault" during the "initial prestart"

...it will not complete the circuit to turn the "go" light on

...or if it detects a "fault" while in use it can warn the operator (there is a problem) by turning the "go" light off


https://www.youtube.com/watch?v=4d4I0PyrgDE
 

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Discussion Starter #14
Method of operation


The operator

...inserts his/her key into the "ignition" switch, located next to the "Big Red Button" Manual Power Disconnect switch

...& turns it to the "prestart" position

...then, waits for the "go" light, on the dash board, to "light up"


This action activates (3) small switches, within the base

...one energizes the precharge circuit

...one sends power to the speed controller to "turn it on"

...one sends power (positive (+) to the "go" light on the dash board


Once the speed controller is "powered up" it "runs" thru its diagnostic prechecks

...if everything is a "go" the controller then, connects the (negative (-) to "light" the "go" light on the dash, completing the circuit


When the "go" light "lights" it tells the operator that, the speed controller indicates that it is "safe" to turn the ignition switch to the "run" position


When the switch is turned to the "run" position

...it releases & unlocks the "Big Red Button"

...which "springs up" energizing the system with "full pack voltage"


The vehicle should now be, ready to be driven


If any issues pop up just "SMACK THE BUTTON" manually disconnecting the "main" power :D
 

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This system would work fine with smaller, low voltage, low power bicycle size EVs. For larger EVs, unfortunately, you've introduced a level of complexity and number of failure points much higher than the original contactor/ fixed precharge system. I doubt if even Data could consistently follow the start procedure for the life of the vehicle, every start. It would have to be every start. Mess up one time, and the controller in a larger vehicle gets blown-out.

The switches(even the small ones, if you could find any) and the fuses will need to be pack voltage rated. I can tell you, from near tragic personal experience, you can't skimp in this area.

Also, larger EVs (~ATV, motorcycles on up) should have an inertia switch that would automatically disengages the HV system with the impact of an accident. This is a required safety feature in most countries. Duncan may even have one in his EV. All of the inertia switches I've seen are low current units working with a main contactor to disengage the HV system.

Maybe, if you want to be "functioning within specified parameters", you should do more homework! I'm guessing if Data has large capacitors in his drive controllers, they have a reliable, automatic, fixed precharge system.
 

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Discussion Starter #16 (Edited)
The "Big Red Button" (BRB) starting procedure is modeled after the international (worldwide)

Diesel 3" - step starting procedure"

1. insert key & turn to the run position (it energizes the system) (Diesel or Electric)

2. "wait" for the light to go out (Diesel-while, it preheats the "glow plugs")(Electric- while the SC goes thru it's diagnostic precheck)

(Diesel- when the "wait" light goes off ) or (Electric- the "go" light comes on)

3. turn the key, again, (Diesel- it starts the engine) (electric- it releases the "BRB" connecting the main power)

When the key is released, the ignition springs back to the run position & the vehicle is ready to go



NOT too difficult, folks have been doing it for years



Yes, your totally right

To "function within specified parameters" we need to look into what these parameters would be...


My motorcycle (we'll look into the bigger stuff later) is operating @ 48V currently


The main specs. we need to know IIRC are

...the pack voltage

...the speed controller power requirements

...& the "go" LED power requirements


So, lets go to the book

According to the Kelly Motor Controller User Manual

http://kellycontroller.com/mot/downloads/KellyKDZUserManual.pdf

...page 4. (2.3 Specifications) ...Controller power supply current, PWR, <150mA.

...page 14. (PM motor wire diagram) ...the red & green LED's require <5mA. <2V each


So,

The "BRB" would need to be able to handle

...48V pack voltage

...up to ~300A continuous (500A peak)


The ignition (or the switches within) would need to be able to handle

...48V pack voltage

...but, only ~200mA.


The fuses would need to be able to handle

Main fuse

...48V 500A

Small power fuse

...48V 5A


https://www.youtube.com/watch?v=IvsyiCmyHXc
 

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Discussion Starter #18
And the inertia switch?

We are currently discussing

...a motorcycle (in my research, I haven't seen any electric motorcycles using inertia switches)

...& a it's a 48VDC system ("We'll look into the bigger stuff later")


§ 571.305 Standard No. 305; Electric-powered vehicles: electrolyte spillage and electrical shock protection.
S1. Scope. This standard specifies requirements for limitation of electrolyte spillage and retention of electric energy storage/conversion devices during and after a crash, and protection from harmful electric shock during and after a crash and during normal vehicle operation.
S2. Purpose. The purpose of this standard is to reduce deaths and injuries during and after a crash that occur because of electrolyte spillage from electric energy storage devices, intrusion of electric energy storage/conversion devices into the occupant compartment, and electrical shock, and to reduce deaths and injuries during normal vehicle operation that occur because of electric shock or driver error.
S3. Application. This standard applies to passenger cars, and to multipurpose passenger vehicles, trucks and buses with a GVWR of 4,536 kg or less,
that use electrical propulsion components with working voltages more than 60 volts direct current (VDC) or 30 volts alternating current (VAC),
nd whose speed attainable over a distance of 1.6 km on a paved level surface is more than 40 km/h.
 

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Discussion Starter #19 (Edited)
Here is some info on "Main contactors" (& their drawbacks)


...it's for electric golf carts but, most of the info still applies


The solenoid in your golf car is the main electrical contactor (switch) that allows battery current to flow to the starter/generator (on gas cars to crank the engine) or to the traction motor (on electric cars). It is a critical component for both gas and electric cars and it is prone to failure because it works so hard, especially in battery powered golf cars. Unlike the starter solenoid in your automobile, which works only as you start the engine, a golf car solenoid must work the entire time the pedal is down. Each time you stop and then restart your golf car the solenoid must also stop working and then start working again. Throughout a busy golf day, the stops and starts can number 1200-1500 per day. These nifty little switches will work for years conducting up to 300 plus amps per use in electric golf cars.

Oddly enough, to reliably conduct all this current and continue to function thousands and thousands of times, most solenoids have a relatively simple design. A steel plunger with a thick plate on one end is surrounded by a coil of thin wire wrapped many times, kind of like a fat spool of thread. When a small amount of battery juice is put across the thin wire, the magnetic field created by the coil throws the steel plunger and plate into two large bolts that stick out of the side of the solenoid case. The two large bolts, or steel studs, and the plate conduct the high current needed to power the starter or golf car motor.
The great advantage to this high amp switch is the plate throws very quickly against the large studs, thereby minimizing the electrical arcing created when connecting high amperage. Picture when you pull a plug out of the wall when the appliance is still on. You see a spark at the wall receptacle. Inside a golf car solenoid this arcing occurs every time the car is stopped and started. It's easy to see why solenoids are the #1 problem in electric cars.
In the early years of golf cars, there were all kinds and designs of multi-solenoid speed controllers. Reliably switching all the battery current required in those early years gave the manufacturers fits. Modern golf cars still have solenoids, but with the advent of electronic speed controllers and regen motors, it seems as though the solenoids do a little better these days. Today, new demands are placed on the solenoid because folks are lifting their golf cars with larger diameter tires and installing larger motors and controllers. This effectively creates the need for greater amperage draw to start the electric vehicle, to overcome inertia. These high currents also take a toll on the Forward & Reverse switch, which is designed to handle 300 amps, more or less.
Regen motor controllers now effectively function as F&R switches by electronically directing the high amperage. The regen controller needs only a low amp signal from a dash mounted F&R toggle switch to correctly switch forward or reverse. Non-regen cars do not have this function so high amperage put through to the F&R switch can create problems. In some cases, installing larger power cables in the car can alleviate F&R problems. Standard battery cable is #6. Installing #4 cable and ends can help. In severe case, a multi-solenoid F&R switch can be installed in your car to replace the mechanical rotary switch. Multi-solenoid F&R switches were common in Harleys, Columbias, Pargos, Yamahas and other early electric and gas cars. They all used a key to change directions. That's because a key switch can handle the small amount of current needed to throw a solenoid. The solenoid does the heavy lifting, so to speak.

Solenoids come in lots of designs with different metals used for the terminal studs and plate. Most common is copper, but years ago silver and silver plate was common. They also come in many different amperage ratings and voltage requirements needed to properly energize the coil so it functions as intended. Some solenoids are designed to work for short periods of time such as the starter solenoid in your automobile. These are intermittent duty solenoids. Golf cars require "continuous duty" solenoids because they are energized the entire time the car is under power. Auto style solenoids will work as a "continuous duty" solenoid for a while but they will prematurely fail.
Lots of things go wrong with these switches. Obviously, the high amps create a lot of arcing at the stud/plate interface inside the solenoid. Even though the plate is designed to slightly rotate with each throw, eventually the stud/plate connection deteriorates, sometimes to the point where it breaks down completely. This is evidenced by the solenoid clicking and sometimes working (car moves), and sometimes not working. Complete failure is around the corner though.
Electric cars are funny. Sometimes when there is a problem here, the failure shows up over there. Loose connections anywhere the heavy battery cables attach (i.e. –the speed switch, the motor, the batteries, F&R switch, even on the solenoids itself) creates a lot of heat build up and, if loose enough, arcing. Remember DC current is what welders use. When a sufficient air gap is established the DC arc melts steel. Solenoids and lead battery posts don't stand chance. Keep all cable connections in the car clean and tight. Inspect them at least once a year. Tightness is not as critical with the small control wires, the control circuit as it is called. Nevertheless, these connections must also be clean and tight.
Another reason solenoids don't work is because the energizing current just doesn't get to the coil. In order that electricity gets to the solenoid winding, it must first pass through the key switch and usually several small micro (or limit) switches often found on the F&R switch and on the accelerator linkage. If any of these switches have failed or if the wires interlinking them have broken or are loose, then current cannot get to the solenoid. Some of these switches are position sensitive. If one gets out of adjustment, even though it works ok, it cannot function.

Another cause of a solenoid not working is there is not enough battery voltage to throw the solenoid. The voltage rating on the solenoid, say 36 volts, is required for that solenoid to work correctly. Batteries can "self" discharge for various reasons. The modern regen cars must be turned off at a special tow switch. If the car is not turned off, the battery pack will self discharge in three to six weeks. Actually, the regen controller's capacitors use the battery pack to stay charged, eventually draining them. Non-regen cars do not have a main cutoff switch for the batteries, but unless there are live accessories, such as a radio with memory, a clock, or a charge indicator or gas gauge constantly on, a fully charged battery pack will maintain a charge for months. Constantly "on" accessories are okay if the car is used frequently but they will discharge the batteries to which they are connected if left uncharged for several weeks. Monthly "catch-up" charges are suggested but not always feasible. We don't recommend disconnecting battery cables because the regen controllers have a particular sequence for disconnect and reconnect. Besides, it usually leads to more problems than it solves, if seasonal storage procedures are carefully followed. Don't forget, discharged batteries can freeze and burst their cases when temperatures drop below 32 degrees Fahrenheit. Fully charged batteries can withstand 40-60 degrees below zero.

The last type of solenoid failure results when the internal plate and studs freeze to each other. In other words, the solenoid works ok, but doesn't stop working when the pedal is released. This results in the car creeping on its own when the shifter is in F or R. Sticky solenoids are more common in the older resistor style cars, but this condition, if not recognized and repaired, can be a fire hazard and at a minimum, cause the battery pack to drain. Lots of folks have seen the result of a sticky solenoid. The resistor coils glow red hot, hence the fire hazard, and why this glowing condition drains the batteries. If this situation happens to you, just shift into neutral each time you stop. Get it fixed right away! Remember that arcing we mentioned earlier? Now that arcing is occurring at the F&R switch, not the solenoid. The F&R is not designed to handle this condition.
A contactor is basically an "electromagnetically driven switch" capable of carry large amounts of current. Inside the contactor are a set of fixed contacts and a set of moving contacts. When the coil is energized, a magnet either pushes or pulls a metal rod and the contacts against the current carrying components.
 

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Discussion Starter #20
Here is some more info I came across (homework) :D

Ampere

The measurement of intensity of rate of flow of electrons in an electric circuit. An ampere is the amount of current that will flow through a resistance of one ohm under a pressure of one volt.

Ampere Rating

The current carrying capacity of a fuse. When a fuse is subjected to a current above its ampere rating, it will open the circuit after a predetermined period of time.

Ampere Squared Seconds (I²t)

The measurement of heat energy developed within a circuit during the fuses clearing. It can be expressed as melting - I²t, arcing - I²t, or the sum of them as clearing - I²t. "I" stands for effective let-through current (RMS), which is squared, and "t" stands for time of opening, in seconds.

Arcing Time

The amount of time from the instant the fuse link has melted until the over current is interrupted, or cleared.

Breaking Capacity

The rating which defines the fuses ability to safely interrupt and clear short circuits. This rating is much greater than the ampere rating of a fuse.
The NEC defines interrupting rating as "The highest current at rated voltage that an over current protective device is intended to interrupt under standard test conditions."

Clearing Time

The total time during the beginning of the over current and the final opening of the circuit at rated voltage by an over current protective device. Clearing time is the total of the melting time and the arcing time.

Current Limitation

A fuse operation relating to short circuits only. When a fuse operates in its current limiting range, it will clear a short circuit in less than 1/2 cycle. Also, it will limit the instantaneous peak let-thru current to a value substantially less than that obtainable in the same circuit if that fuse were replaced with a solid conductor of equal impedance.
Disconnect Mounting
The disconnect mounting allows the fuse unit to be removed (off load) using an insulated hook stick. The hook-stick grabs a pull ring and disconnects the fuse unit, which may then be lifted out of its mounting.
End Fittings
End fittings are metal parts that attach to each end of a fuse unit’s ferrules (end caps). As previously mentioned, they are used solely with disconnect fuse applications or when converting a non-disconnect to a disconnect fuse configuration. When end fittings are ordered, a fitting for each end of the fuse is included. Keep in mind that end fittings can become damaged in use and, therefore, are sold separately from the live parts when necessary. It is not necessary to purchase an entire set of live parts when only the end fittings are required.
High Speed Fuses

Fuses with no intentional time-delay in the overload range and designed to open as quickly as possible in the short circuit range. These fuses are often used to protect solid state devices.
Live Parts
Live parts were discussed as part of the “Mounting” definition. Everything above the insulators on the mounting excluding the fuse unit, fuse holder, and the fuse end fittings (if required) are considered the live parts. Fuse end fittings are discussed next and are not required with non-disconnect
live parts, but are required and included with disconnect live parts. Live parts may be sold separately as replacement parts or for new OEM applications.
Melting Time

The amount of time required to melt the fuse. Link during a specified over current.
Mounting
A mounting provides all the necessary parts to safely mount a fuse in its intended piece of equipment. The base is the metal support to which all other pieces attach. Insulators attach to the base and insulate the live fuse unit from the base and everything beyond the base. Live parts are the parts of the mounting that are energized once electricity is flowing. The live parts provide the means to hold the fuse unit in place, electrical contact, and a place to make line and load connections.
Non-Disconnect Mounting
A non-disconnect mounting does not provide a means for removing the fuse unit until the circuit is dead and the fuse unit can be removed manually. The fuse unit is held in place by friction through the use of fuse clips or by a cross bar.

OHM

The unit of measure for electric resistance. An ohm is the amount of resistance that will allow one ampere to flow under a pressure of one volt.

OHM`s LAW

The relationship between voltage, current, and resistance, expressed by the equation E=IR, where E is the voltage in volts, I is the current in amperes, and R is the resistance in ohms.

Over Current

A condition which exists on an electrical circuit when the normal load current is exceeded. Over currents take on two separate characteristics--overloads and short circuits.

Overload

Can be classified as an over current which exceeds the normal full load current of a circuit. The current does not leave the normal current carrying path of the circuit--that is, it flows from the source, through the conductors,
through the load, back through the conductors, to the source again.

Peak Let-Thru Current, IP

The instantaneous value of peak current let-thru by a current limiting fuse, when it operates in its current limiting range.
Power vs. Distribution
The differentiation is intended to indicate the test conditions and where fuses are normally applied on an electrical system, based on specific requirements for generating sources, substations and distribution lines. Each class has its own unique set of voltage, current and construction requirements (see ANSI C37.42, .44, .46 and .47).
Replaceable Fuse Unit:
A replaceable fuse unit is a phrase used to describe a fuse that does not have a separate holder and refill assembly. In a replaceable fuse unit, the fuse is its own holder and is completely replaced after interruption.

Resistive Load

An electrical which is characteristic of not having any significant inrush current. When a resistive load is energized, the current rises instantly to its steady state value, without first rising to a higher value.

R.M.S. Current

The R.M.S. (root-mean-square) value of any periodic current is equal to the value of the direct current which, flowing through a resistance, produces the same heating effect in the resistance as the periodic current does.

Short Circuit

An over current which exceeds the normal full load current of a circuit by a factor many times (tens, hundreds or thousands greater). The over current also leaves the normal current carrying path of the circuit--it takes a "shortcut" around the load and back to the source.

Voltage Rating

The maximum open circuit voltage in which a fuse can be used, yet safely interrupt an overcurrent. Exceeding the voltage rating of a fuse impairs its ability to clear an overload or short circuit safely.
 
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