tag:blogger.com,1999:blog-6161778274523938171.post1562849757058998035..comments2019-10-22T14:00:42.923-04:00Comments on Watt's Up?: Watts and volt-amperes ratings – what’s the difference and how do I choose an inverter based on them?GaryRhttp://www.blogger.com/profile/13342106993487479289noreply@blogger.comBlogger7125tag:blogger.com,1999:blog-6161778274523938171.post-7002882796824111982017-06-14T14:37:12.359-04:002017-06-14T14:37:12.359-04:00Hello Gary,
Its because I am trying to ensure I d...Hello Gary,<br /><br />Its because I am trying to ensure I don't overload a transformer, but the transformer is rated for 70VA and I want to put the loads on my transformer, but all of the loads are rated in W Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-6161778274523938171.post-88802144465006925772017-06-13T15:42:45.550-04:002017-06-13T15:42:45.550-04:00Hello Anonymous,
Using the device from a transfor...Hello Anonymous,<br /><br />Using the device from a transformer implies an AC input. So if the datasheet uses this scenario to specify the AC current at a specific AC voltage, the VA rating is simply the product of these two numbers. The rating of 20 W alone does not give you any insight into the VA rating (other than it is >= 20) since you don't know the power factor (pf) which could be anything from 0 to 1. Since the definition of pf = W / VA, then VA = W / pf, so for your example, VA = 20 / some number between 0 and 1. As I mentioned above, this will yield any number >= 20.<br /><br />I wonder why you want VA. Usually the VA number is used to calculate or estimate W and/or current, but you are already given those numbers, so you really don't need VA.GaryRhttps://www.blogger.com/profile/13342106993487479289noreply@blogger.comtag:blogger.com,1999:blog-6161778274523938171.post-73038986576919074042017-06-13T13:34:33.823-04:002017-06-13T13:34:33.823-04:00Hi,
Sorry to ask this question so much later aft...Hi, <br /><br />Sorry to ask this question so much later after this post, if I had a product that was rated for 20W but it can go both on AC or DC power, how would I determine the VA exactly for the product when the datasheet only gives the watts and the current if I was to put the device on a transformer?Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-6161778274523938171.post-55699050214533391452017-01-02T11:04:44.143-05:002017-01-02T11:04:44.143-05:00thanksthanksMahmoud Kasbanhttps://www.blogger.com/profile/01865452825666857389noreply@blogger.comtag:blogger.com,1999:blog-6161778274523938171.post-16329777706425551552015-07-06T15:51:03.574-04:002015-07-06T15:51:03.574-04:00Hello Anonymous,
I can assure you that the differ...Hello Anonymous,<br /><br />I can assure you that the differences between W and VA are not at all controversial like the PMPO vs RMS issue as it applies to the audio industry. W and VA each have clear, indisputable mathematical definitions. Please refer to this article I wrote back in 2012 for those definitions and more information: http://electronicdesign.com/energy/what-s-difference-between-watts-and-volt-amperes<br />GaryRhttps://www.blogger.com/profile/13342106993487479289noreply@blogger.comtag:blogger.com,1999:blog-6161778274523938171.post-25976800060717944332015-07-05T11:02:49.830-04:002015-07-05T11:02:49.830-04:00Sorry, but I still do not understand the differenc...Sorry, but I still do not understand the difference between VA and Watt. What is the difference between 'apparent' power and 'real' power? For me this should be the same for VxA=W... It looks like sales talk to me...? Like PMPO and RMS watts for audio... a sales gimmick. Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-6161778274523938171.post-73654101014401784852013-06-07T08:54:42.053-04:002013-06-07T08:54:42.053-04:00Thank you for info.Thank you for info.Devrim Baris Acarhttps://www.blogger.com/profile/11875901330530001421noreply@blogger.com