SolarJackets - Motor Controller Group
Programmable Motor Controllers
Motor controllers range in complexity from simple switches operated manually (ie switch on cordless electric drill) to highly sophisticated programmable motor controllers which may be found in electric vehicles. They are used to control features such as RPM or torque and protect motors from conditions that may damage it such as overheating or too much current. This paper analyzes a few state-of-the-art, commercially available motor controllers, the underlying theory of motor controller operation, and summarizes the implementation of controllers in regard to electric vehicles.
Commercially available motor controllers
Some of the key specifications that vary between controllers include the minimum and maximum operating voltage and peak current. The Zilla Z2K-EHV can handle up to 2000 Amps and has a voltage of 72 to 348 Volts with a peak power of 640,000 watts  and its cost is $4675  . Other motor controllers specifically for brushless DC (BLDC) motors with various specifications and features vary in cost from $399 to $2699 but are suited to significantly lower maximum voltage and peak current than the Z2K-EHV . Since every motor controller has significantly different features (ie warranty, number of microprocessors, software interfaces, number of inputs) , it is difficult to gauge whether this is “reasonably” priced without knowledge of the Voltage or current flowing from the battery. Should the maximum power flowing from the battery be significantly below what the Z2K-EHV can handle, this would obviously eliminate Z2K-EHV from further consideration. The Performance Motion Devices MC73110 motor controller IC  is an alternative and appears to have a promising API (ie allows development of application with C/C++) to the above but it does not list the peak current or max voltage that it can supply to the motor. According to the listing, it appears to come as just the IC without the analog circuitry.
Underlying Technology of Motor Controllers
As stated earlier, different motor controllers can have more or less functions or features depending on its complexity. All motor controllers have the same primary function however. This function is to regulate the power flowing from the battery to the motor in response to user input to the acceleration pedal . The acceleration pedal is connected to a potentiometer which controls how much voltage is sent to the motor. If the driver doesn’t push the pedal at all, the potentiometer allows zero voltage to the motor. If the pedal is floored, the max operable voltage is sent to the motor with a duty cycle of 100 percent. Otherwise, pulse width modulation is used to obtain an average voltage somewhere between zero and the max voltage . For example, pushing the pedal halfway down would yield a square wave with a duty cycle of 50% and, thus, an average voltage of half the max voltage. The frequency of the pulse sent to the motor in most DC motor controllers is usually larger than 15,000 Hertz making it outside of the range of human hearing and thus virtually silent.
Implementation of Motor Controller
All of the motor controllers researched seem to come as kits with each their own manual and software-hardware interfaces and parts. The manuals also describe how to assemble the parts and connect the controller to the motor. The biggest challenge thus appears to be to program the controller to maximize the efficiency of the motor and all other features to be controlled. Additional microcontrollers and/or sensors may be required to obtain additional feedback data and measurements from the motor to further increase efficiency as well.
 Café Electric LLC. Owner’s Manual for the Zilla Motor Controller Package with Hairball 2 Interface. [Online]. Available: http://cafeelectric.com/downloads/HB202.pdf
 Café Electric LLC. [Online web page]. Available: http://cafeelectric.com/shop/index.php?main_page=index&cPath=1
 Kelly Controls LLC. [Online web page]. Available: http://www.kellycontroller.com/120v-brushless-kblkbl-ikhbhp-controllers-c-23_43.html
 Performance Motion Devices. MC73110 Motor Control IC datasheet. Available: http://www.pmdcorp.com/downloads/MC73110_Motor_Control_Chip_Datasheet.pdf
 Integrated Publishing. Nuclear Power Fundamentals. Electrical Science Fundamentals Handbook (Volume 4 of 4). Motor Controllers. Available: http://www.tpub.com/content/doe/h1011v4/css/h1011v4_127.htm
 M. Brain, “How Electric Cars Work”, [Online article] (27 March 2002) Available: http://auto.howstuffworks.com/electric-car2.htm#
 N. Kruschandl, “Solar Car Anatomy – Motor and Drivetrain” [Online web page]