get 240 volts at a home or business that doesn't have 240 volt outlets is t o pick off two outlets that are wired to separate circuits on opposite side s of the 240 volt power. There is a commercial product for this and design s on the web. I found this schematic.
Plug one plug in. The other now has live power on one of its pins (via K3 c oil) if either of K1 or 2 relays fails closed. If you touch that live pin, K3 closes connecting the person to live via the battery charger. Do relays fail closed? They sure do, especially at high current. I don't know about t he US, but it would not be legal here in UK.
t 240 volts at a home or business that doesn't have 240 volt outlets is to pick off two outlets that are wired to separate circuits on opposite sides of the 240 volt power. There is a commercial product for this and designs on the web. I found this schematic.
t
om the circuit. This also causes K3 to drop out no matter what since there is no closed circuit for the current.
gerous situation.
t
s coil is cut. But if an input is reversed the input relays still close. In this situation the initial voltage to K3 is only half and I very serious ly doubt the relay will kick in. This can be verified in the specs. If th e minimum drop out voltage is above the maximum voltage you will see on the input, this is not a problem.
An ordinary relay generally does close on half coil voltage. Of course the contact pressure is then less than half rated.
New ones here look a bit like that. Old ones are far more basic, typically just 4-8 wire fuses and a switch, all in bakelite on wood. The 8 way here is typical:
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A 1930s one, 2 circuits, dual pole fusing:
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Not many of those left in the wild. Pre-1960s wiring here is not at all ok.
These are Solaris Urbino12 Electric buses. The line round trip distance is 13 km and according to the schedule, there would be at most 10 min charging time from the pantograph at the city terminal. .
The moment the coil is de-energised the relay opens. Therefore the spring i s pulling the contacts open, and the coil's force pushes them closed. Conta ct force is then coil force minus spring force. Thus halving coil current g ets you less than half the contact force.
Once the contacts are closed it takes less force to keep them closed than i t did to get the thing moving. That does not change the facts in the previo us paragraph. Now a relay may be perfectly happy operating like that, but I would not expect it to result in as much reliability/life under high curre nt use.
240 volts at a home or business that doesn't have 240 volt outlets is to p ick off two outlets that are wired to separate circuits on opposite sides o f the 240 volt power. There is a commercial product for this and designs o n the web. I found this schematic.
ems the issue is that without the input relays when you plug the unit into one outlet the path through the output relay coil can energize an exposed p lug pin. But I don't see the need for two poles. Running the 120 volt con nection through the input relay contacts on just one side of the output rel ay coil will prevent the two inputs from being energized when only one is p lugged in.
only advantage I can see is that with the two pole relays a single stuck co ntact won't be dangerous. In a one pole approach it can pass a dangerous v oltage to the input plug pin. But you can hear relays working so a stuck r elay can be detected. Also it has indicators on the inputs so you can tell the relay isn't clicking because of a failure rather than simply no voltag e. So this risk seems minimal.
sed.
AFCIs have been mandatory for all new construction for nearly 10 years now, and they incorporate a "machine ground fault interrupt" with 30mA trip thr eshold, versus the 5mA for the GFCI you're thinking of. The hack will trip circuits with modern interrupters. It could be ELECTRONIFIED by discussion of available autotransformer techno logy, which is being rapidly displaced by fairly inexpensive, and certainly more energy efficient, switching technology products.
e the contact pressure is then less than half rated.
g is pulling the contacts open, and the coil's force pushes them closed. Co ntact force is then coil force minus spring force. Thus halving coil curren t gets you less than half the contact force.
I did that when I was a kid. Which bit do you think incorrect?
The only relay where spring force is the only controller of contact force i s the bistable relay. K3 is not a bistable, the circuit would work bizarrel y if it were.
In our products, I will apply full voltage for turn on and then PWM that volage down using the relay coil as the inductor, to reduce power. As the relay coil heats up, it takes more voltage to hold it closed so I place the voltage at some happy place in-between.
That probably has diddly squat to do with this discussion though.
Well how about this - what the hell is so complicated here ?
That "schematic" is nothing but a bunch of wires. What the hell are the rel ays for ? They make a neato clicking noise to make you think it is doing so mething.
Bottom line is it has two 120 inputs, and you can get 220- (that IS the old school double of 120) as long as you hit both sides of the mains coming in .
You don't need a board or any shit for that. Just take your meter and find two outlets where the hots measure 220 against each other and there you got . Boom done.
So you just wire the two hots, smaller blade, copper color screw, to the tw o copper colored screws on an outlet for a big A/C window unit (20 or 25 am ps), electric drier (about 30 amps) or electric stove (50 amps). That depen ds on what you need and how much you can pull from the two circuits.
The relays do nothing and they also don't make it code, maybe. the NEC requ ires that both sides of a 220 must break in unison. (words to that effect, I am not a tape recorder)
Looks to me like you find two circuits to feed that thing and the relays ma ke that cool sound to tell you that you have indeed found both sides of the 220. If both inputs are on the same side then no click and no work.
I know I can derive 220 in most houses by finding the two sides. (I won't c all them phases) but it can only be code IF:
The two branch circuits from which you feed are properly protected AND you install a tandem 220 breaker OF LOWER RATING than either of the branch circ uits coming in.
The contact pressure is not determined by the coil current. The armature has two hard stops, and is metastable between. It's like a toggle switch; it snaps.
The opening spring is usually a coil spring, but is sometimes a flexure. The closing force is usually determined by flexure of the contact leaf, but on some bigger relays is a separate, visible spring per contact.
Maybe the confusion here is that I said "spring force" determines contact pressure. That could be interpreted as "the force of the coil spring", which isn't what I meant.
(Reed relays are an exception; that is one of several reasons why they are unreliable.)
--
John Larkin Highland Technology, Inc
picosecond timing precision measurement
jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
Some DC relays and solenoids have extra contacts that reduce coil current once the armature is seated.
AC relays do this automatically; when the armature seats, coil inductance goes up so coil current goes down. Industrial users prefer AC relays for that reason; the coils run cooler than DC relays, so are more reliable.
--
John Larkin Highland Technology, Inc
picosecond timing precision measurement
jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
urse the contact pressure is then less than half rated.
ng
ays
ring is pulling the contacts open, and the coil's force pushes them closed. Contact force is then coil force minus spring force. Thus halving coil cur rent gets you less than half the contact force.
e is the bistable relay. K3 is not a bistable, the circuit would work bizar rely if it were.
There's a fair bit of confusion here. I'll start by clearing up the terms: spring force: the force from all the springy parts, regardless of what shap e coil force: the force produced by the solenoid, not including the contribut ion of any spring.
Now, you say an ordinary relay works like a sprung toggle switch. If it did , it would be a bistable relay, it would not open when coil power is remov ed. Obviously it does open then. Inevitably, fundamentally inevitably, when powered there must necessarily be 2 forces acting on the contacts: spring force & coil force, and they fundamentally necessarily must be acting in op posing directions. If you don't have those conditions, you don't have a sta ndard relay. You'd either have a bistable relay or a device that never swit ches.
Some modern relays may have spring force that varies significantly with con tact assembly position, but toggle switch snap action it simply can not be.
I said that it snaps like a toggle switch. You can't halfway set a toggle switch. You can't trim the coil current to hold the relay armature in an intermediate/halfway position. Try it.
Increase and decrease the coil voltage slowly. The armature doesn't creep; it snaps between two stops. It's metastable between.
When the coil is sufficiently energized, the armature slams against a hard stop, usually the core piece inside the coil. More coil current won't make it move any further than seated. When the armature is seated, the force on the contacts is determined by some springy couplings between the armature and the contact pairs.
There are lots of reasons to design relays this way.
--
John Larkin Highland Technology, Inc
picosecond timing precision measurement
jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
Not sure what you base this on. There are more than one company designing battery powered trucks which are not so unlike buses in terms of their requ irements for batteries. In case you didn't realize, both trucks and buses are heavy to start with. The expense is not a problem since that is not th e spec used to select a truck or bus. They care about life cycle cost and EVs have a huge advantage in fuel costs. Over the life of a truck or bus t his far outweighs the cost of the battery even at today's prices. Then on top, the amount of maintenance is much less for EVs saving even more money.
So in reality it is the ICE vehicles that are monstrously expensive.
Rick C.
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