The most basic form of switching DC motor controller is the DC chopper. It consists of a single silicon switch, a freewheeling diode, some capacitors for filtering out current spikes and electronics for controlling the switch.
Controller Diagram
The main switch is turned on and off at a high frequency, typically 15-20kHz. When the switch is on, current starts to increase in the motor since the battery is now connected across it. When the switch is off the motor current flows through the freewheeling diode. Motor resistance and diode losses causes the motor current to decrease towards zero Amps.
By adjusting the amount of time the switch is on versus the amount of time the switch is off the current flowing in the motor can be controlled. The torque the motor outputs is proportional to the current flowing through it. What this means for my EV is that I can control acceleration by controlling the on time of the switch.
IGBTWhile browsing through the local surplus store, I came across a number of IGBT modules rated at 400A and 600V. I decided to buy two and base my controller around them.
IGBT motor controller
The modules are quite suitable since they contain a full half bridge with freewheeling diodes. By clamping the upper IGBT in off state I end up with the main switch and diode I need for my motor controller all in one neat low inductance package, well two actually.
I opted to use two IGBT modules in parallel since I'll need about 400A to accelerate from a standstill. While the modules are rated at 400A, a single module would quickly overheat due switching and conductance losses. Using two gives me more margins and twice the surface area to dissipate the heat.
HeatSink
Speaking of heat; a decent heat sink is absolutely vital to keeping the IGBTs cool and happy. I found a large surplus heat sink online at surplus sales of Nebraska.
They also had some IGBT mountable snubber capacitors that I decided to get. These mount directly to the IGBT modules eliminating stray inductance which could otherwise cause IGBT destroying voltage spikes.
snubber
You make it sound so simple.
Do you have a more detailed description like schematics so I cn duplicate it fo my EV-project?
// Lots of Love from Sweden.
I too would like a more detailed description of the IGBT motor controller. Looks like a simple and affordable solution, but some more details as to connections/which terminals to use/hookup to throttle, etc. would be very helpful. And how well is it performing for you?
Thanks.
