T7 US voltage requirements

[Blake]

Just ordered a T7 and it arrives tomorrow. Probably a stupid question but what are the voltage requirements for theT7 in the U.S.? 110v or 220v. I recognize I am showing my ignorance here. I will be able to support either in my home shop but the 220 will require a little more set up.

[Rob]

far as I'm aware US standard voltage is 110V 60Hz??

UK is 240V 50Hz

[Ken S]

Rob is correct. Some power tools with large motors are wired to work with 240 volts in the US, however, the T7 only draws 200 watts, and is well within the limits of 120 volts.

Just plug your new T7 in a standard power receptacle and you should be good to go.

Ken

[Blake]

Thank you guys, excited to get this tomorrow and begin sharpening the Tormek way. 

[Herman Trivilino]

far as I'm aware US standard voltage is 110V 60Hz??

UK is 240V 50Hz

Rob, we also have 220 volts available in all homes built or wired in the last 50 years or more. We use it for water heaters, kitchen ovens, clothes dryers, and central air conditioners. In the shop it's not unusual to find a 220 volt table saw or air compressor. Typically there are two hot wires, each at 110 volts, but 180 degrees out of phase. And it's at 60 Hz, of course. Commercial applications differ in that they will use a three phase transformer and typically get 208 volts from two of the three 110 volt legs. You have to be careful in that application because refrigeration compressors designed to run on 220 volts will quickly burn out when run on 208 volts.

The one thing I'd like to have is one of your 220 volt tea kettles. It would have to purchased there and then wired up here. Not sure if it would meet code, but a UK outlet for a tea kettle would make a nice conversation piece.

[Rob]

I've got a mate who emigrated State side manny years ago and the first thing he took after returning home for the first trip was a kettle. Culturally coffee is drunk more routinely than tea so he too struggled to find a decent kettle

I can always buy one and post for you. You could probably PayPal gift me the money??

[Ken S]

Herman and Rob,

I don't know that the fifty hertz vs sixty hertz would make any difference with a heating element. I would guess a simple adaptor from UK standard to US standard would do the trick. The lower US voltage should just take longer to heat. I have seen plug in tea kettles with standard US plugs.

Being a Neanderthal, I have used a gas range and a plain kettle for decades. i use a plastic Melitta filter holder and filter for coffee and just a tea bag for my wife's tea. It is inexpensive and it works every time.

As a telephone man, my work was a branch of electricity. One thing I found fascinating was the early standardization of electricity in North America versus in the UK. I recall that at one time, there were twenty seven different kinds of electrical power in the UK. North America standardized almost completely quite early. I say "almost" because different systems have persisted until to day in some very small pockets. Also, my great aunt gave me a typewriter many years ago which she used in an office building in Boston which had DC power, a rare holdover from Thomas Edison. It's a fascinating story.

Ken

[Herman Trivilino]

The lower US voltage should just take longer to heat.

Double the voltage and you get four times the power, so yes, it takes a lot longer to heat. That's why I like them better in the UK.

[Herman Trivilino]

I can always buy one and post for you. You could probably PayPal gift me the money??

Thanks for the offer, Rob. I'll take you up on it if I ever get around to running the wiring to my kitchen.

[Jan]

I don't know that the fifty hertz vs sixty hertz would make any difference with a heating element.

This apparently simple question takes us very quickly into deep waters, Ken. 

The frequency of the voltage causes power oscillations during the heating. The instantaneous power oscillation is double frequency of the voltage. Nevertheless the voltage frequency does not influence the speed of heating the water for your coffee, because the produced heat is proportional to the time averaged power. 

The voltage frequency and the number of poles define the synchronous speed of an induction motor. For example if the frequency is 60 Hz the synchronous speed for a 4-pole motor is 1800 RPM while for the frequency 50 Hz this speed is only 1500 RPM.

Slip causes that the real rotor speed of an asynchronous motor is lower. E.g. 1400 RPM instead of 1500 RPM for a 4-pole motor and 50 Hz frequency.

Jan

[Ken S]

Jan, I was a telephone man, not a motor man, therefore, I welcome your thoughts.

Herman, if I remember electrical theory correctly, power (watts)= electromotive force (volts) x current flow (amps). I recall current flow with 220 volts as half the flow with 110 volts. The lower current means less heat produced, but the power should be approximately equal. Please correct me if this is incorrect.

Ken

[Elden]

PIE

Power (watts) = I (amps) x E (volts)

[Herman Trivilino]

Herman, if I remember electrical theory correctly, power (watts)= electromotive force (volts) x current flow (amps). I recall current flow with 220 volts as half the flow with 110 volts. The lower current means less heat produced, but the power should be approximately equal. Please correct me if this is incorrect.

P=IV where P is power (in watts), I is current (in amps), and V is voltage (in volts). You are correct in that if two devices are consuming the same power, then the one with twice the voltage will have half the current. An example is a transformer. Assuming none of the power is used to increase the temperature of the device. So if you have a step up transformer that doubles the voltage it will cut the current in half.

In the case of the heating element in a tea kettle when we double the voltage we also double the current, assuming the heating element obeys Ohm's Law. Ohm's Law, often written as V=IR, asserts that if the resistance R is constant then the voltage is proportional to the current. Thus doubling V results in I becoming twice as large. Since P=IV, if we double both I and V then P quadruples.

In reality the resistance R of a heating element is not constant, it increases with temperature. If you have two identical tea kettles being used to make tea, one in London operating at 220 volts and the other in Houston operating at 110 volts, their heating elements would be at the same temperature. So it's a good approximation.

Anyway, I've witnessed it happening. I didn't measure the time but I did notice that the tea kettle in England made the water boil a lot faster. My wife was so enamored with our daughter's electric tea kettle in London that when we got back home she bought one. I warned her that it wouldn't work as well and as it turns out I was right.

[Jan]

Well explained, Herman. 
I am surprised that the kettle survived the London story.

Back to Ken's question:

I don't know that the fifty hertz vs sixty hertz would make any difference with a heating element.

Imagine we have two kettles.
One (US) is designed for 110 V, 60 Hz and the input power 1500W.
The other (UK) is designed for 220 V, 50 Hz and the same input power 1500W.

Which kettle will boil the water faster? Does the voltage frequency influence the time necessary to make the water boil? In my thinking there will be no time difference between those two kettles.

Jan

[Ken S]

Jan and/or Rob,

In the US, kitchen appliances (and power tools) usually have the design constraint of having to work on a 15 amp circuit without popping the breaker. That's why a "3 1/2 horsepower" router is not really that horsepower. I believe the euphemism is "developed horsepower".

With European power at 220 or 240 volts, the example 1500 watt tea kettle would only draw about 6.8 amps. Are the British tea kettles normally rated at around 1500 watts or would higher wattage units be typical?

What is the current load of a typical kitchen circuit?

Ken