Current draw - 2003 tiger

[Sam Hough]

Hello,

Sorry, I'm confused again.

Our main drive motors say max amps 14.1A but controllers and armortek fuses at 40A (each).

I can understand belt and braces on the controllers but not better to use 15A fuses? or do the motors operate over 14amps?

Cheers

Sam

[Adrian Harris]

The fuse is there to protect the VTX motor drivers, which have a 40A rating and 55A limit.

Also, the start-up current for the PM60 motor is stated as 3x the maximum load current.

Having blown 40A fuses on several occasions, I can't see a 15A fuse lasting very long

Adrian.

[Adrian Harris]

Here's a thread I started when I had a running Sherman:

www.armortek.co.uk/Forum3b/viewtopic.php?f=7&t=85&p=561

Adrian.

[Sam Hough]

Thanks!

Very helpful. I was about to buy some 30A rated inline meters. They can handle 100A for 100ms but probably not up to it.

Thanks. You have saved me some exploded parts.

How did you manage to blow the fuses?

Thanks

Sam

[Sam Hough]

It is surprising that the toggle switch is rated at 80+ amps!

[Adrian Harris]

> How did you manage to blow the fuses?

They've mainly been in the T-34. I knew it had worn sprocket rollers, which I had a assumed was the reason the track locked on occasion, but in fixing them I found that the roll pin holding the crown gear in position had broken at both ends, so the crown gear could float on the drive shaft and was locking the drive when it didn't engage in the worm drive properly.

Most of the time it seemed to lock at low speed, and I knew I could clear it by reversing for a short distance, but if it locked at full speed, the fuse blew.

I've heard it mentioned that Ohm's law might come into play if you're running the tank with depleted batteries, as they won't be producing their full voltage, hence the current ought to increase to compensate. Personally, I'm not sure if such a simple formula is valid in something as dynamic as motor control.

Adrian.

[Sam Hough]

Very interesting.

Could you hear anything going wrong?

One of the reasons I'm interested in measuring this stuff is to spot possible problems early on.

Main reason is just geekiness. Dad has chosen style of the gauges : http://ellen.redspr.com:8080/

Thanks

Sam

[Adrian Harris]

I run the T-34 with very loose tracks, so they slap around quite a bit. It would be driving fine then just stop dead. Sometimes more dead than others

Adrian.

[Mark Heaps]

It is surprising that the toggle switch is rated at 80+ amps!

Not at all surprising. The easily replaced fuse will blow well before the toggle switch can be damaged. That is what fuses are there for, to protect the more expensive parts from damage and therefore should have the lowest rating out of any of the components.
Mark

[Sam Hough]

At the risk of further exposing my ignorance: The toggle switch has "15A 250V" written on it. It is SPDT but only one side is for the 24V circuit. I imagine the rating has a lot to do with immediate "switch on" current and it would be tough to turn the tank in with full throttle enabled.

It obviously is fine. I'm just missing something. I work with an ex-electrical engineer so I'll see if she can educate me.

Thanks

Sam

[Mark Heaps]

At the risk of further exposing my ignorance: The toggle switch has "15A 250V" written on it. It is SPDT but only one side is for the 24V circuit. I imagine the rating has a lot to do with immediate "switch on" current and it would be tough to turn the tank in with full throttle enabled.

It obviously is fine. I'm just missing something. I work with an ex-electrical engineer so I'll see if she can educate me.

Thanks

Sam

SPDT is Single-Pole Double-Throw. A change-over switch, although if only two terminals are used, it is then effectively an on-off switch.
In your case the 15A is the maximum constant current it can withstand. The 250V is the maximum potential the insulation can withstand before breaking down and arcing to other metal components in the vicinity ( mounting plate etc)and / or arcing between the contacts.
Mark

[Sam Hough]

Well I asked two electrical engineers (with an MSc each) and they don't know why the switch doesn't melt

I think I'm going to move on with my life and just accept that it doesn't.

Thanks for all the help.

Cheers

Sam

[Armortek]

Sam

The switch operates a relay. The relay switches the power on and off and carries the load current. On our models the max current can go up to 80 amps for very short bursts. The 40 amp fuse can cope with this and so can the relay. On the very latest models with the Motion Control Module the main fuse is uprated to 60 amps and the max current can exceed 100 amps for very short bursts. This is why the new models out perform the older ones.

Those who fit a battery isolation switch should have all this mind, because such a switch should be rated at 100 amps, and will consequently be enormous.

Mark

[Sam Hough]

Thanks Mark,

I'm really losing my grip. I've not seen the relay in real life or on this drawing: http://www.armortek.co.uk/Forum3b/viewt ... 047#p51224

Is it the wrong drawing or am I reading it wrong?

I was trying to find a replacement switch and they are enormous

It obviously works I just get worried when I fail to understand it.

Thanks

Sam

[Sam Hough]

Assuming you are THE Mark: Many thanks for these great kits. Dad and I are really enjoying it.