Plug braking.

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Link   100 MW

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Plug braking.

Post by Link » Feb 10 2008 4:29am

I know of a few ways to do this:

Ghettoest way is to just short out the leads to the motor with a relay or something. Not that great. You'd fly off if engaged at higher speeds, and it heats the motor unnecessarily.

Better way is with a big resistor and a relay. Flip on the relay, power gets diverted to the resistor, braking ensues. Only one power level, though. (Unless you use more relays.)

Best way is to use a controller to control the amount of power going to the resistor. This acts the most like a mechanical brake. Costs more, however.

EXPERIMENTAL WAY is to use a transistor capable of dissipating a lot of power. It could be controlled via a simple pot, and would not cost much. Just a cheap potentiometer and a big MOSFET (array?). But, I don't know if any transistors would be capable of dissipating that much power. You'd probably be fine if you go over the limit for short periods, but you might encounter a problem if you were using it for something like controlling your speed down a hill.

Regardless, you'd need a big fat heatsink.

Any thoughts?
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TylerDurden   100 GW

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Re: Plug braking.

Post by TylerDurden » Feb 10 2008 10:30am

A few thoughts have been shagged in the regen threads.
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fechter   100 GW

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Re: Plug braking.

Post by fechter » Feb 10 2008 11:52am

By using FETs, you can parallel a bunch of them. Something like a IRFB4110 can dissipate around 300 watts if you have enough heatsink. A combination of FET and resistor might be more practical, since it's easier to get a resistor to dissipate tons of heat.
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monster   100 kW

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Re: Plug braking.

Post by monster » Feb 10 2008 5:40pm

is there a circuit diagram for this fechter?

i've got a home-made variable resistor on my plug brake (croc clips and wrapped nichrome wire). its not variable from the handle bars tho :?

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fechter   100 GW

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Re: Plug braking.

Post by fechter » Feb 10 2008 6:11pm

I'll whip one up. Might take a while. I haven't used FETs in the linear mode much.
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fechter   100 GW

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Re: Plug braking.

Post by fechter » Feb 11 2008 11:04am

OK, here you go:

Use 3 bigass FETs like IRFB4310's mounted on a really big heat sink.
The 3 1N4004 diodes supply voltage to drive the gate (just a single one might work OK). A 10v Zener keeps the gate voltage limited to 10v. A voltage divider supplies the gate voltage. The control pot will go from full off to full on braking. The braking force will not be linear with the control, and there might be a way to limit the voltage range to make it more linear, but that might add complexity.

I'm not sure if the connection to battery negative is necessary, but it won't hurt.

I forgot to draw in some fuses for the phase wire connections. It would be a good idea.
Non Regen Motor Brake 2.jpg
Non Regen Motor Brake 2.jpg (22.93 KiB) Viewed 1146 times
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