contactors?

[Jay64]

So what is the difference between using a contactor and a on/off switch? Is it just because of the high power being used that a bigger switch is needed? And how important is it to use pre-charge resistor and a contactor coil suppression diode when using a contactor?

 

[Jay64]

Background on what I am looking to use that might need a contactor if that makes a difference on the answer. Right now I am planning on using an Etek RT motor with a 48v 10ah lifebatt pack and possibly a 7234 alltrax controller.

 

[TylerDurden]

A contactor is basically a big mofo relay. It allows using a small switch at the controls, at a different voltage. A precharge resistor with the switch or contactor is a good idea, as it reduces wear due to arcing.

 

[fechter]

The coil suppression diode goes across the relay (contactor) coil to suppress the high voltage spike that will happen when you disconnect the power. If you're powering the contactor coil from a switch, and that switch does not go to anything electronic, then you might get away without the diode. In general, the diode does not need to be very high amp rating, so not very expensive.

Without the precharge resistor, the contacts could weld shut and not open when you want them to. In some setups you can get away without it, but it will cause the contacts to wear out very quickly. Precharge resistors are cheap too. I use a 470 ohm 5 watt, but the value is not very critical.

 

[Jay64]

So a contactor connects to a switch, or it is a switch? Would I use one for making a kill switch, or just a regular on/off switch?

 

[rkosiorek]

contactor is just another word for RELAY. it is used so that you can remotely control large currents using a small switch and wiring. this saves a lot of copper and a lot of unwieldy power wiring.

all of the heavy duty wiring goes to the contactor. the contactor would normally be mounted close to the batteries and motor to keep the runs of high-power wiring as short and direct as possible. the contactor/relay is activated by a coil controlled by a switch and low power wiring. it would be used as part of an on/off switch

kill switches as used by racing organizations are simple mechanical switches. the simpler the better. located where it can be accessed from outside of the vehicle. the idea is that in case of accident the electrics can be completely disabled by the safety crews. a contactor cannot be used here.

kill switches as used by hobby and sports guys are set up so if the rider falls of of the vehicle the vehicle will be powered off. a contactor could be used as part of the circuit here.

rick

 

[Jay64]

My idea of a kill switch is a switch on the handle bars that instantly turns the vehicle off in case something goes wrong (stuck throttle, stuck carb slides, shorted throttle or controller, bike laying on it's side with a WOT stuck in the dirt). Can a contactor be used for that?

If I had a regular switch near the battery and motor, I wouldn't need a contactor? I'm assuming that my ezip doesn't have one. It seems to have a toggle switch inline between the battery and the controller. I guess I don't see the reason for having a contactor instead of a toggle type switch on a bike except for using a kill type switch on the handle bars. I could see the point of having a on/off switch remotely controlled in a car where you would be sitting a long ways away from the battery and motor. I'm not trying to argue or anything, I'm just trying to see if I undertand this correctly. I was recommended to get a "72 volt contactor, or a 12 volt would work if you have 12 volts on board for the lights. best one is the Tyco lev 72 volt , at $140."
Does that mean that regardless of how many volts I am running, I can run a 12 volt contactor if I have a 12v system running?

 

[fechter]

Right. Thats what I do on my scooter. The contactor (relay) is powered by the same dc-dc converter that runs the lights and cooling fan. I have a kill switch on the handlebars that operates the relay. There is a separate key switch that turns on the dc-dc and enables the precharge resistor.

 

[Jay64]

So what is a good contactor to get? Is this Tyco lev 72 volt overkill?

 

[Jay64]

Ok, I got the Kelly 24v-72v400a contactor. I tried looking on their website for any type of instructions or maual, but didn't find any. How exactly would I wire this up, including where to put the diode and resistor?

Sorry the focus is a little bad.

 

[michaelplogue]

If you want something compact, the Crydom solid-state relays are about as small as I could find. Still haven't hooked mine up yet, but it definitely takes up less real-estate that the traditional coil relays.... They are a bit pricey though..

http://www.google.com/products?hl=en&q=crydom+solid+state+relay&um=1&ie=UTF-8&sa=X&oi=product_result_group&resnum=1&ct=title

http://www.alliedelec.com/Catalog/Indices/Products.aspx?Ne=2315&N=4294828503+4294958822&M=1&sid=11ADA3EF65A4

.

 

[Jay64]

Thanks for the info, but at this point I am not looking for advice on what contactor to get, I already have this one. I am looking to find some information on how to hook up the one I have.

 

[michaelplogue]

Well, judging from the pic: You'd connect your 12V battery with switch in series to the two smaller contacts on top. Then (what I'd do) is cut into your positive lead on your main line from the battery, and connect both to the large terminals on the bottom. When you close the switch on the 12V side, the connection is completed on the high-voltage side.

 

[Link]

I'd check the contacts with a multimeter, just to be sure. The coil will probably register in the ~100-200Ω range.

 

[Jay64]

So this one does need a 12v supply?

 

[TylerDurden]

It appears to be a 72V coil, no need for 12V.

 

[TylerDurden]

Here is fechters pre-charge diagram:

You won't need the resister on the relay (contactor coil), since it is rated for 72v.

 

[Jay64]

Thanks TD. This might be a dumb question, but the Fechter's diagram looks like it has 4 connections to the contactor, but my contactor has 6. Am I just completely misreading the diagram?

 

[TylerDurden]

I only see four in your pic...

If there are 6, it may have two coils: both energize to draw the contactor closed, then just one is used to hold it.

 

[shinyballs]

Thanks for the diagram Tyler, For the Kelly Main Contactor CZ10-150 72VDC Coils 150Amps
http://www.kellycontroller.com/shop/?mod=product&cat_id=12,28&product_id=320

Is the wiring for this contactor the same as above? can't seem to understand the coil suppression diode, is it built-in in the contactor?

It would be very useful if this info is added under -
Board index ‹ Electric Vehicles ‹ EV Basics

Is this possible moderators?

 

[TylerDurden]

@shiny
The two small lugs are for the coil and the two big lugs are for the power to the motor.

The diode fechter mentions in an add-on: IIRC, he said to just bridge it across the coil terminals to reduce the spike when power is cut to the coil (at shutdown).

 

[TylerDurden]

FWIW, this is an old contactor for one of my cars. It has the two coils, and has two sets of contacts: one normally-open and one normally-closed. The switch on the side is for turning off one coil when the contactor is activated.

 

[shinyballs]

Would this be it? sorry about the crude drawing...

 

[shinyballs]

is this the right way?

 

[frodus]

No, that won't precharge. The precharge 1k 5W goes to the controller.

The engine kill switch is a toggle on off switch on the handlebars. That is what drives the contactor. Look at the circuit again.

Key switch on puts a small trickle of voltage to the controller to precharge the capacitors inside the controller. Wait a second for the voltage to come up so that the potential on the controller caps is the same as the battery pack (72V). This eliminates the ARC on the contactor, increases life... and the caps like the gradual change in voltage instead of being slammed on.

Once Its precharged, Toggle the KILL switch from OFF to ON, and you're contactor should close. This is good too, because if the key OR the kill switch goes off, you kill the contactor. Its double safety. You can't turn it on without the key AND the kill switch off.