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Re: (ET) Hybrid Electrak?



On 1/15/2011 10:35 AM, Banks, Michael J. wrote:
I was under the impression, that using the tractor while charging was a
bad thing.

That depends on the charger. There are a couple of circumstances where using a charger on a running EV could cause damage.

- The noise from the charger could damage control electronics or simply cause it to be confused. The battery does act as a nice filter for lower frequency disturbances though. - The charger cannot react quickly to load changes(0). EVs will produce rapid load changes. The worst case is probably going from full torque to zero torque(1). All of a sudden the voltage will rise as the current is diverted to the battery. This could damage the control, the charger or the battery if not limited. A near fully charged battery will be more of a problem in this case.
        - It would also play havoc with any charger's end of charge 
determination.

However given a good clean DC source with a good fixed maximum voltage with a fast response there is no reason to expect a problem. A PM motor rotating at a fixed (or strictly limited maximum) speed is almost ideal for this.

Robert

0 - This is part of the reason that you'll often see chargers say the charger must be off before disconnecting the battery, they cannot react to the sudden load change quickly enough.

1 - Even worse is on an EV with regen when you go from full torque in one direction to full torque in the other. Imagine the following scenario. Vehicle takes 200A from the bus in full acceleration, battery provides 100, charger provides 100. The vehicle then switches to full regen returning 200A to the bus. The battery has now one from sourcing 100A to sinking 300A (100A charger, 200A regen). Now regen and accel currents will not often be this symmetric but it should be obvious that dramatic changes in current at the battery are possible complicating the charger's needed response.

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