206
Chapter Nine
Throttle Ramp Shaping Throttle ramp shaping affects the PWM output response relative to the throttle position. The more ramp shaping the throttle circuitry has, the more control the operator has over low speed (see Figure 9-9).
Plug Braking This feature uses the dc electric motor to slow the vehicle down, much like regenerative braking, but without placing energy back in the batteries. The current is routed back into the dc motor armature, creating a braking force. Note: Plug braking is not recommended for on-road EVs. The plug-braking feature is intended for materials handling and low-speed, low-load applications only. Plug braking can be completely eliminated by not attaching a power cable to the A2 terminal on the controller and the A2 terminal on the dc motor (see Figure 9-9).
Basic DC Motor Controller Circuitry Layout Figure 9-12 provides you with a glimpse at the basic working and functional controls contained within the controller. Speed control is achieved by what is called the throttle potbox (Figures 9-10 and 9-11). The potbox has a standard variable 0- to 5-kΩ resistance. The 0- to 5-kΩ resistance is standard for most motor controller throttle controls (a 5-kΩ pot wired as a two-terminal rheostat). A Curtis PMC potbox or any 5-kΩ pot will work fine. For controllers with other input options, you can use other optional throttles for the vehicle. See Chapter 11 for accessories.
Basic DC Controller Vehicle Wiring Layout Figures 9-13 through 9-16 display the most basic of wiring and layout of components for your EV conversion. This is only a sample, and your wiring may differ depending
Figure 9-10 Potbox (Curtis PB-6). (www.curtisinst.com.)