Design considerations for a PWM controlled low voltage disconnect (LVDC)

Abstract

Valve Regulated Lead Acid (VRLA) batteries have been used in telecommunication power systems for over a decade and with them has followed demands on the handling of batteries at low voltages. Devices connected in series to the system are often incorporated to disconnect the batteries from the load in the event of a near deep discharge. This paper covers the design considerations for one such device that improves reliability through the use of Pulse Width Modulation (PWM) techniques. By choosing a low voltage contactor and regulated PWM input, a voltage range covering both 24V and 48V systems can be achieved that greatly improves efficiency and reduces thermal stress, hence reducing the size of critical components. Detailed analysis of the total system reliability and EMC issues are also presented.

Development of a new IC-controlled interchangeable AC and DC contactor

“…A less voltage will be imported on the excited coils to supply the suitable electromagnetic force for the making process of the conductor. Comparison to the conventional conductor with the single source for the exciting coils, the research by Walcott [12] points out that the power consumption can be reduced by 86% if the pulse-width modulation (PWM) is implemented as the voltage control method for the exciting coils of the conductor. And, the consumption of power will save up to 30-60% due to the smaller radius of copper used for the less power consumption case.…”