A~C Controller & Motor Technology Lowers the Total Cost of Ownership (TCO)

The key elements of the drive system of any electric vehicle are the battery, the speed controller and the motor.
Simple put the purpose of a motor speed controller is to take a signal representing the demanded speed, and to drive a motor at that speed. The electric vehicle power source is the lead acid deep cycle battery delivering direct current (DC) over a number of hours, batteries are typicall rated using amp/hours. The motor converts supplied curent into rotation to drive the vehicle.

Older electric vehicles use DC controllers and motors. These controllers have one major drawback, they consumed some of the available amps thus reducing the overall number of hours available to drive the motor. The DC motor also has a drawback in that it uses small brushes inside the motor. These carbon brushes are one of the least costly parts in an electic motor. On the other hand, they usually are the key part which delivers the durability ("life-time") and performance to the motor they are used in. The call out time and down time of the motor are the biggest cost factors with this type of motor.

The new generation A~C controllers take the DC current and convert it into alternating current (AC) and regulate this to the amount needed by the motor to reach the desired speed.
The A~C controller is a sophisticated microprocessor controlled device and can also contribute to lower operating costs via regenerative braking.
The motor when driven takes current from the battery and converts this to rotation, under braking this 'free wheel' rotation can be used to generate current that is put back into the battery, regenerative braking. A motor and a dynamo are in effect the same device.

The total cost of ownership can be expressed as:
COA + ( AMC + ARC ) x Y = TCO

COA = Cost of acquisition of the vehicle
AMC = Annual maintenance cost
ARC = Annual running cost
Y = Years of vehicle life

The A~C motor and controller combined have three major advantages over the DC controller and motor that will lower the total cost of a vehicle over its lifetime (TCO)

1) Batteries last longer between recharges as no power is lost within the controller.
2) Regenerative braking tops up the battery while working
3) Cost of maintenance, no brushes need replacing and no work time is lost waiting for, and during a service.

A major manufacturer produced the following data over a period of 2,500 hours of vehicle usage. This data does not include the savings from increased operating hours or regenerative braking as above.

	Petrol	Diesel	DC	A~C
Fuel / Energy costs	£4500	£4500	£720	£600
Maintenance cost	£2750	£2750	£2500	£1470
Total	£7250	£7250	£3320	£2070

This table illustrates how a petrol or diesel vehicle can have a lower COA but the cost of fuel and maintenance greatly increase the TCO after the sale.
An electric vehicle will have a relataively higher COA but the running and maintenance costs are much lower over the vehicle life.
The A~C vehicle has lower maintenance costs and lower running costs due the contribution from regenerative braking.


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