transformer sizing
- Thread starter matlark
- Start date
Transformers 101
Actually, there is no "Fudge Factor". A Transformer is one of the things that you can count on for 100% ampacity, for 100% duty cycle.
If you have a 600va load, you will never get there with a 500va transformer.
What is your application? 500va is only 1/2 amp at 120vac.
If you are working on ONE machine, buy a transformer with spare capacity. If you are engineering a purchase for 10 or more machines, then you must understand your load, and size the transformer for adequate capacity, and economics in design.
Actually, there is no "Fudge Factor". A Transformer is one of the things that you can count on for 100% ampacity, for 100% duty cycle.
If you have a 600va load, you will never get there with a 500va transformer.
What is your application? 500va is only 1/2 amp at 120vac.
If you are working on ONE machine, buy a transformer with spare capacity. If you are engineering a purchase for 10 or more machines, then you must understand your load, and size the transformer for adequate capacity, and economics in design.
Andy6
Member
A 500VA transformer CAN supply more than rated, possibly 600VA or more, but only for very short amounts of time. The amount of time depends on the cooling you can provide and the overload VA you are trying to get.
But in anycase, building from new, always err on the side of caution and upsize. You never know who will come along later and start adding more loads to a maxed out transformer.
But in anycase, building from new, always err on the side of caution and upsize. You never know who will come along later and start adding more loads to a maxed out transformer.
My experience is that while power transformers will generally have a fairly conservative rating small control transformers do not. In addition it is quite common for people to install these transformers without really considering the cooling requirements. Deliberately overloading this type of transformer for long periods of time is a recipe for a fire.
As the rating is VA (Volts x Amps) the performance is relative to the Power factor of the AC load.
the Idea of doing load calculations is to protect your transformer.
As you excede the VA ability of the transformer you create other problems.
Apart from the fire risk, a 600 Watt load is not 600 VA, so why would you attempt to use a 500 VA Transformer
the Idea of doing load calculations is to protect your transformer.
As you excede the VA ability of the transformer you create other problems.
Apart from the fire risk, a 600 Watt load is not 600 VA, so why would you attempt to use a 500 VA Transformer
Mark Snodgrass
Member
Actually, 500va is just a hair over 4amp (4 x 120 = 480) and it is 1A on the 480V side
Tell my local power company that. They engineer pole-mount transformers to run at 150% capacity.
i'm assuming its because they are oil filled transformers. Whenever they do pad mounts, they spec them for their rated loads.
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