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# A Relay Circuit for Wide Range of AC Line Input

IP.com Disclosure Number: IPCOM000014105D
Original Publication Date: 1999-Sep-01
Included in the Prior Art Database: 2003-Jun-19
Document File: 2 page(s) / 45K

IBM

## Related People

Malik, R: AUTHOR [+2]

## Abstract

Problem Server systems and other critical applications require continuous operation without any downtime. This requirement is generally met by using redundant AC sources and AC/DC power supplies. The power system which consists of more than one power supply in parallel is powered by at least two line cords where one of the AC line cord is connected to the main AC line while the other is connected to a motor generator (M-G) set via uninterruptable power system (UPS). When main AC line drops, the relay K drops to the default connection and the UPS starts providing power to the system. When AC returns, the relay K switches to the main AC line contacts and thus the power is always made available to the system without any system interruption. The available commercial relays are either for 90-137V or 160 -265 Vac input application. It means that the systems have to be configured either for 90-137V or 180 -265V AC input. This becomes a problem for systems that are designed to operate over the wide range of AC input (90 -265V). Problem Solved Figure 1 shows the relay arrangement to switch from one AC source to another. The relay K in Figure 1 can be used either for 90-137V or 180-365V AC input.

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A Relay Circuit for Wide Range of AC Line Input

Problem

Server systems and other critical applications require continuous operation without any downtime. This requirement is generally met by using redundant AC sources and AC/DC power supplies. The power system which consists of more than one power supply in parallel is powered by at least two line cords where one of the AC line cord is connected to the main AC line while the other is connected to a motor generator (M-G) set via uninterruptable power system (UPS). When main AC line drops, the relay K drops to the default connection and the UPS starts providing power to the system. When AC returns, the relay K switches to the main AC line contacts and thus the power is always made available to the system without any system interruption. The available commercial relays are either for 90-137V or 160 -265 Vac input application. It means that the systems have to be configured either for 90-137V or 180 -265V AC input. This becomes a problem for systems that are designed to operate over the wide range of AC input (90 -265V).

Problem Solved

Figure 1 shows the relay arrangement to switch from one AC source to another. The relay K in Figure 1 can be used either for 90-137V or 180-365V AC input.

The circuit in Figure 2 describes the principle of using the same relay for 90-265 Vac. A resistor Rx is switched in and out of the coil winding of the relay to adjust the current through the winding. The resistor Rx can be switched in and out of the circuit by the switch S1 connected across Rx. The switch S1 could be a manual or electronic switch. S1 is closed for 90-137...