Thread: Crazy idea?
View Single Post
Old 12-11-2015, 07:38 PM   #8
JohnnieB
Techno-Nerd
 
JohnnieB's Avatar
E-Z-GO
 
Join Date: Jun 2011
Location: West Virginia
Posts: 19,654
Default Re: Crazy idea?

Quote:
Originally Posted by Helirich View Post
So why do people buy a 500 amp controller if there is no benefit over a 275?
Tangible benefits are received from controllers over 275A.
With a 500A controller, a series wound DC traction motor will produce 82% more low end torque than it will with a 275A controller and with a 600A controller is will produce about 120% more low end torque. However, top speed does not increase with a higher ampacity controller.

The net result is that you can haul/tow a heavier load and that you can accelerate from a standstill faster and that the cart can climb a steeper hill without stalling the motor.

However, once the motor is spinning above the RPM at which it cannot draw more than 275A, there is little performance difference between a 275A, 500A, 600A or 2,000A controller, other than the higher ampacity controllers are less likely to overheat when worked hard.

I don't have a Torque vs RPM curve for a stock series motor, but I do have one for an aftermarket motor and the principle is the same even though the specific RPM and torque numbers are not the same.

Connected to a 48V battery pack, the unnamed motor can draw 526A and produce about 80ft/lb of torque at about 1,000RPM
Same motor connected to same battery pack can only draw 408A and produce 60ft/lb of torque at about 1,250RPM.
Same motor connected to same battery pack can only draw 291A and produce 40ft/lb of torque at about 1,575RPM.
Same motor connected to same battery pack can only draw 231A and produce 30ft/lb of torque at about 1,800RPM.

At some RPM between 1,575 and 1,800, this motor cannot draw more than 275A, so below that RPM there is a significant performance difference with a higher amp controller and above that RPM, there isn't.

FWIW: The motor in the example has over 15HP (About 11.5 @36V) while a stock series motor is only about 2.5HP.

Since this motor can draw over 500A at low RPM, a 600A or larger controller is needed to obtain maximum performance from it. A 500A controller is about all a stock series motor can handle and about 450A is max for a PDS motor.
JohnnieB is offline   Reply With Quote