Summary
The contactor economizer is used to lower the standby consumption of the solar car. It minimizes the required amount of energy through the contactor, just enough to keep the contactor connected. This is done by using Pulse Width Modulation (PWM) and meanwhile we monitor the amount of current used to keep the contactor connected. This innovation can be used in any scenario where a contactor is used, to optimize power consumption for every contactor used in the system.
Detail
To achieve this innovation, we need to disconnect the battery pack for savety reasons. This way the solar car is completely disconnected from the rest of the electrical system. For this purpose a mechanical separator must be used. The mechanical seperator we call a contactor. The contactors are electrically controlled so that the safety system in the car can act when needed. Heavy relays are used because the amount of current that flows out of the battery pack is relatively high. A small amount of current is needed to activate the contactors. Only a very small amount of power is consumed whenever the car is in standby mode. Compared to this the contactor consumes too much power, which is why we want to optimize this power consumption. The relay requires less current to stay connected than it needs to connect at first. So whenever the contactor is connected we can decrease the current and with it the power consumption of the connector. It is important to not decrease the amount of current too much, so that the contactor can not disconnect when we do not want it to. Decreasing the current can be done by using a resistance in the circuit. However, a resistance always cause a loss of energy, so this is not the best solution to our problem. That is why we use Pulse Width Modulation to reduce the current in the most efficient way as possible. We call this the contactor economizer.
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