Heavy Weight Speedos

**big_nipper** · 25th January 2007, 18:14

Daniel, if you want to make sure the current limter can act fast enough on LEMs with the roboteq all you need is to add a suitable sized choke on both motor wires, If you can find out from the manufactures what the minimum inductance the roboteq needs then a choke (inductor) of that size or bigger will protect the speed controller and limit the motors current.

The problem will be in order to fully protect it from a stalled motor that you will find that power will be quite low, I guess around 200 watts or so, so you will seriously be down on power, and the choke will be quite big.

Why not try the MAG28-400 motors thats what we now use in big nipper with the Dogsbollox controllers, dont know if they will fit in mute though

**mute** · 25th January 2007, 18:50

Haha, nice, I bet Big Nipper is fun running on Mags.

Im not too worried about peak amps, a short burst of 100+ amps doesnt matter, its more the sustaned high amps. We want to cut Mute back to about 80-100 amps to protect the motors. As it was we were heating the armature and warping it until it was touching the magnets... not to mention turning the spindle blue. Lemco advised us to use 100 amps max for 5 mins to prevent damage :sad:

The only reason Im steering away from DogsBollox is that Ive got no idea what the current limit was set to on our speedos as they are de-restricted. I guess its gotta be high as we were de-soldering the anderson connectors (both on the board and the incomming wires).

Is there any way to know what the current limit is without trying to stall our motors and measure it? If there is, two new FET boards will be the cheapest and easiest option.

**storm** · 25th January 2007, 19:35

Daniel - borrow a clamp meter and 50m of bell wire submerged in water !

Ed
http://www.teamstorm.com http://www.teamstorm.com

**jamesb** · 25th January 2007, 19:53

Hmmm, ive got a spare pair of 4QD 200s, just need a spare pair of LEMs!

make me an offer, i might let my 2 lems go.

**big_nipper** · 26th January 2007, 08:09

The 3 fet boards in big nipper, are set around 120 Amps (ish) but for some reason the weapon one (Still on CIM2 motor) causes the motor to cut in and out when on the current limit. This did happen on one of the MAGs also but we increased the current limit (dont know what it is now) and the problem went away.

We set this by stalling the motors and measuring the current! No stalling it for more than a few seconds at a time. At least the fet boards have a small LED that lights when you hit the current limit.

I doubt Dogsbollox will current limit the LEMS to any reasonalble level, as they use a hall-effect type curent pickup on the battery +ve which I assume will have a relitatively long delay before the current limit kicks in, due to this and the LEMS low inductance, basically I cant see the current limit working without a choke, but a choke might still be the simplest solution.