This transformer is not a toy. It's not a travel accessory, as it weighs over 20 pounds.
Now I'm in the market for a used Hottop roaster. Since I'm now in the U.S., I'm going for a 110V Hottop. I've seen numerous references to the advantages of running a Hottop through a Variac or other voltage regulator. Here's my question:
Would it be advantageous to run the 110V Hottop through the transformer but set the transformer output to 110V (i.e., input 110V, output 110V). Would this not have the effect of regulating the voltage somewhat?
I don't have any voltage testing equipment, so I'm asking for an educated opinion.
Posted Fri Sep 6, 2013, 7:22am Subject: Re: Using a transformer as voltage regulator
All transformers are ratio devices. In other words, their output will be a ratio the input that depends on their windings and internal resistance. For a step up/down transformer, it's important to know what the input (i.e. line) voltage is. For transformer spec'd with a 110V primary, if your line voltage is something like 125 VAC (higher than specified line voltage is not uncommon), the output will be approximately 1.136x the nominal output specification (i.e 220VAC x 1.136). A similar calculation would exist if your line voltage was lower than spec but in the other direction.
I checked the website of your step-up tranny and it's not clear whether it includes any VR circuitry to mitigate this effect of your line voltage. Even so this won't accomplish what you can do with a variac unless your only goal is to feed the roaster a constant defined voltage. I haven't read all the threads on the Hottop, but I'm guessing that folks use a variac to control roast temperature more precisely than the Hottop's controls permit. In particular, it could be used to stretch out the roast by "starving" the heating elements. Your step-up won't provide this level of control.
At any rate, if you're going down this road, get a good multimeter. You'll want to know exactly what the VAC output of the variac at different rheostat settings.
Posted Fri Sep 6, 2013, 10:54am Subject: Re: Using a transformer as voltage regulator
When my 1500W Behmor is drawing full power my line voltage varies from 116V to 119V.
If I had a Variac, I could adjust it up to fluctuate between 119V to 122V. That might result in somewhat faster roasting and darker roasts with larger batch-size.
I think you understand it right: With a Variac you can move the whole range up or down …but you still will have the variation.
Voltage regulation would be more expensive.
If you were going to buy a multimeter, why don't you start off with a $20 Kill-a-Watt meter, which gives you voltage, current, watts and several other less-used variables, to a device plugged into it. I have a Fluke multimeter but …the Kill-a-Watt meter is much more convenient.
Yes. This is one reason to want well-designed power supplies with good isolation on all the things whose performance would be noticeably affected (computers, audio equipment, that big flat screeen, etc).
I think I will pony up for a multimeter. Most of my friends have them, and maybe I'd come across less like the liberal arts ditz that I am if I owned one of these.
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