Monthly Discussion
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Wireless / Micro at an Affordable Cost
The RCM4400W and RCM4510W based on the Rabbit 4000 microprocessor, offers customers greater freedom to develop with wireless Ethernet / Wi-Fi or wireless ZigBee / 802.15.4 as their communication link in their Industrial Control, RTU or Building Automation applications. For limited time RCM4400W and RCM4510W development kits are available at a price of $199USD regularly priced at $299USD. Get yours today! MasTec will add GST, shipping and handling to these prices of $50NZD on these units. Total $340NZD +GST to get started playing micro and wireless games. Offer stops end of Sept
linkThis month we are going to discuss UPS specifications.
You need to be very careful in reading the specifications on UPSs.
The main buying criteria for a UPS is how much power can it put out and secondly how long can it do this.
Take for example how manufacturers spec their UPSs. The biggest game is in the VA rating. If they can make that high, it makes the UPS look like it is strong and can support a big load.
For example a 1700VA UPS may actually be a 850 watt UPS with a PF of .5. (power factor)
For example a 1700VA UPS may actually be a 1000 watt UPS with a PF of .6. (power factor)So if you take the same UPSs, 1700VA unit, and rearrange the spec a little,
The 1700 speced at .5PF now with a PF of .7 it really is a 1200VA UPS.
The 1700 speced at .6PF now with a PF of .7 it really is a 1400VA UPS.Which would you buy the 1700 or the 1400 or the 1200, well actually they are the same UPS just speced differently.
So ask the question. Most of our UPSs are speced at .7 PF these days, but some like the low cost IPs and Titans are still at .6 PF
Next we look at batteries and runtimes.
Many of these over speced UPSs fail in runtime also because they have lower battery capacity, just to keep the price down. Batteries make up about 30% of the cost of the UPS and putting a little battery in, will save some dollars.
So for instance, take a typical quasi sinewave UPS, one of our Titan 2000VA UPSs which has qty four 12VDC 9 amphr batteries. This is 430 watthrs of battery ( 12*9*4) actually very hard to get the batteries to be fully 100% charged and they deteriate with age, so lets say 400watthrs are so called available or stored in the lead. It all changes when you load the batteries as you will see in the calculations next.
So if we take a 2000VA UPS like this and load it up to its 1200 watt limit, how much time do you get? Well only about 20-25% of the energy in the batteries will come out before the battery reaches the turn off level of 10.5VDC, if you are very lucky, so we have 100 watthrs and the inverter is usually 85% efficient if you are lucky, so really only 85 watthrs can come out as AC. Runtime is 85/1200*60minutes or 4 minutes and that is on new batteries, give them a year or two and you are down to 2-3 minutes, certainly not enough time to shutdown a server.
So if we take the same 2000VA UPS and load it up to its 600 watt limit, how much time do you get? Well only about 30-35% of the energy in the batteries will come out before the battery reaches the turn off level of 10.5VDC, so we have 120 watthrs and the inverter is usually 90% efficient if you are lucky, so really only 110 watthrs can come out as AC. Runtime is 110/600*60minutes or about 10.0 minutes and that is on new batteries, give them a year and you are down to 7-8 minutes, certainly enough time to shutdown a medium server running at 400watts probably about 15 minutes.
That probably amazes you, if you are not a technical person but those are the hard facts, I could show the battery graphs. The amazing thing is this, it is like as if the battery has shrunk on you, were did all that stored energy go to. Well it is still in the battery but the voltage of the battery is too low for the UPS to run and it can't be extracted. Note if you drop a battery voltage down to low on discharge it will only last a few cycles of charge - recharge so it is a compromise of sucking the battery dry and battery lifetime.
So the general rule for light weight UPSs like IP, Blazers, Titans and all those other models out there, is to load them lightly and you get longer runtimes.
Just looking at battery charts for these small SLA batteries tell you they do not like putting out high currents before they reach the terminal shut off voltage.
That is why if you compare say a Titan 2000VA UPS to a Gamatronic, TrippLite, Soltec or Alpha 2000VA there is a huge difference. These UPSs all have battery capacities of greater than 700 watthrs and are more efficient and runtimes under heavy load is much longer, but the cost is higher.
Ask our staff to help with all of this and get what you require to do a good job.
Hope this helps.
************************************************************* MasTec has been publishing this newsletter each month but you may have noticed we have not mailed out on it for the last 3-4 months now.
It is not that we have forgotten you, we have been extremely busy moving AC~DC Power next door and setting this all up again.
We have everything in place again, server, mail and website also accounting and database, so it is business as usual for AC~DC Power Ltd.
We are encoraging distributors and sub distributors to buy from AC~DC Power Ltd now.
All Sales -- Administration
Saera Tui All Sales -- Management
Rob Maskell Instrumentation Sales
Loyal Noronha AC & DC Power Sales
Dhara Pandya General Sales
Mancy Gaonkar Dealers Sales,
Jeannie Murdoch Liason Officer for Product Development
Rob Maskell (Please send Jeannie Murdoch in Marketing any updates on company details, any new staff members etc)
Winner of the Soltec 400VA UPS for June was Jack Farley, Congratulations Jack.