The electric car motor controller takes the input from the batteries and in most cases, turns it into three-phase alternating current which is supplied to the electric motor.

This is only the basic job of the motor controller. The controller takes information from the accelerator pedal which tells the controller how much power to supply to the motor. The electric car motor controllers are the brains of the electric car.

The controller has many jobs to do and because of this, it uses an electronic chip which is programmed with certain information. If a powerful motor is used with a battery pack capable of powering the motor to its fullest capabilities, it’s quite possible to damage the transmission system if the accelerator is opened fully and suddenly, but the controller is programmed to prevent this excessive torque.

If a fault occurs in the motor or electrical circuits, or the motor overheats for example, the controller can shut down the system until the fault is rectified, saving the vehicle from any further damage.

The controller also prevents the batteries from being over-charged and tells the motor when the minimum voltage is available from the batteries. The battery minimum voltages are often misunderstood. It is a big mistake to take power from the battery right down to the point when nothing more can be taken. If this is done, damage to the batteries can result preventing them from becoming fully charged in future and shortening their life, so minimum battery level checking is a very important feature.

It is also responsible for accepting the signals from the Drive / Neutral / Reverse switch do provide the correct power to the motor for these functions. The controller can also prevent the motor from turning the wrong way when the car is stopped on an incline. For example, if the car is in Drive, and it is stopped on an upward incline, the controller senses this and will not let the motor turn in the opposite direction. This has the effect of assisted hill start or hill-hold.

The controllers for DC motors are different. The controller does not change the input DC voltage to AC three-phase, but instead, regulates the voltage supplied to the motor depending on the setting of the accelerator.

If the controller detects a fault, it can be queried electronically by an electric car engineer to allow the engineer to see the problem and hence it is an excellent assistant in diagnosing faults.