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#### Duncan

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6,652 Posts
I'm running an 11 inch Hitachi motor with a P&S controller
I have been feeding it 1200 amps and 340 volts - I was hitting 6800rpm at the end of the 1/4 mile
Just doing a rebuild and increasing the maximum voltage to 390 volts plus changing the diff to cut the rpms by 14%

The motor is rated at 200 amps, 48 volts and runs at about 1400rpm in the forklift

One of my friends (Brian) is just building a drag bike
We have got a Chevy Volt battery pack (390 volts) and a Crown 11 inch motor
Brian has ordered a Zilla high voltage 2000 amp controller

Its looking good - but only a maniac (Brian) would ride a drag bike

#### Duncan

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6,652 Posts
Series motor voltage constraints is oddly enough the gap between commutation segments and corresponding flash over which erodes the comm bar and brushes super fast. Total voltage determines what current you can push and power made. In @Duncan 's case it might zorch if he ever gets to above 75% "on" in the duty cycle at low rpm.

Having said that, realize a motor is an inductive load. The faster it spins, the more back EMF is going to resist forward voltage with zero rpm having the highest current demands. Therefore, it is possible that motor may survive the + 300 volts at redline rpm.

Kostovs with added interpole magnets are tested to survive 300 volts but also have an 8 degree retarded comm timing and do not generate the same levels of HP to prevent zorching

500 lbs isn't that odd, Kostovs are 220 lbs and 500 is about the weight of a 7 liter gasoline engine
Hi Piotrosko
I hit 100% "load" at low rpms - but at low rpms that only needs a small voltage - so the controller only feeds the motor a small voltage

With a DC motor the three values are all linked - current, rpm and voltage

To get a high voltage you must have high rpm and high current - so at low rpm my controller can only feed a low voltage

So I can't "get to above 75% "on" in the duty cycle at low rpm" - unless the controller fails - in which case it will probably zorch the motor !