Re: More drag racing questions (torque)

[Victor Tikhonov <vtikhono@lsil.com>]

Paul, you're missing the point!

The torque is proportional to current and before back emf limits you,
the current proportional to voltage, Ohm's law.

If you are telling me that dynamometer hooked to the stalled motor shaft
shows identical ft*lb torque value whether I apply 0.01V to it or 10V 
(unlimited current power supply), sorry, you are wrong.

They will rotate at different speeds, true but free rotating shaft has
no definition of torque. You can always (for DC motors) find such
rpms in these cases that at torque values are equal and call it 100%
or full, but that 100%'s are not comparable and have no meaning

There is no such thing as just 100% torque.

100 torque of your car is not the same as 100% torque of diesel loco,
even at the same rpm.

Paul G wrote:
> 
> >Is 100% torque at 5V is the same _ft*lb_value_  as 100% torque ft*lb
> >value at 1000V?
> 
> Yes, its full torque, as in all the torque the motor will ever make at the
> controllers current limit. For a Prestolite MTC-4001 that would be 64
> ft/lbs at 400 amps.
> 
> The difference will be the rpm. At 10 volts you might come out of current
> limit at 200rpm, at 100 volts perhaps 3200rpm
> 
> Oh, at 1000 volts most of the motors we use will make NO torque. Just
> commutator flashover and rapid spontanious dissasembly. Of course you will
> let all the smoke out of your inverters too <g>
> 
> Neon