Posts on Jan 1970

UPS Systems Upgraded

All MCS hosted services are now running on a double conversion power system. Better voltage = happier servers. MCS completed the upgrades last night to replace an aged line interactive system. What’s the difference between a line interactive and double conversion UPS you may ask. Well, it all comes down to cleanliness of power delivered to the equipment.

A line interactive UPS will normally just pass through whatever power is coming from your utility. If your utility delivers 124 volts, that is what is getting passed to your equipment. In the event of a power outage, the UPS has to sense the outage and then quickly replace that power with power from its battery. This causes and issue because the time in between the power going out and the UPS batteries kicking in, you are left with no power being delivered to you equipment. This is a very short window, measured in milliseconds, and most servers will have enough charge in their power supply capacitors to buffer through the outage. Sometimes though, a server might have a strained power supply, or the UPS takes a little bit too much time to kick in and this will end up with the server starved or power and it will reset. Also, since these UPS systems pass through power they are not a good fit for use with generators. Generators generally produce dirty power that can possibly damage sensitive equipment.

A double conversion UPS is much different. These devices will constantly use their internal batteries to output clean voltage within a specific range. So, 124 volts from your utility company go into the UPS and 120 volts come out to your servers. Also, since these devices are on-line all the time, in the event of a power loss there is no loss of power to the equipment. The battery will simply start to drain and not be recharged via utility power. On-line double conversion UPS devices are also better suited for use with a standby generator. When the generator kicks in, dirty power with nasty looking squared of sin waves goes in and clean power comes out thanks to the battery conditioning. These devices have a downside though. They are more expensice to purchase and to operate. Since power is not being passed through directly, more total power is consumed to power the same loads leading to a little increase on the power bill. Also, since the batteries are being used all the time, they wear out more quickly then a line interactive system and require replacement sooner.

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