Help With Math, Calculating Total Amps

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Motor Gen sets

Yes the older models would be like combined-have some older electrical books that discuss them.I was thinking of the later models that had an induction(or synchronous motor for really large ones)Has anyone seen an elevator machine room?-You will find a M-G set there-they work really well in this application.most larger elevators have DC motors to drive the host mechanism for the car.Its said when the elevator car is descending-the elevator host motor is acting like a generator.The motor gen sets don't mind the voltage fed back into them and "cushions" the descent by acting as a active load for the host motor.Besides boiler rooms-elevator rooms are fascinating to me.Have enjoyed watching the quipment-on mid shifts you had to have work collegues take rides so you could watch the equipment.And vice versa.The elevator motors come as two types-direct drive traction-the motor is connected directly to the host capstan.Gear drive-the motor drives the elevator cable capstan thru a geared down gearbox-for even greater torque.Used on freight elevators.Passenger elevators use the direct drive traction system-for greater speed.the elevator motors are compound wound DC.New motors are permenent magnet DC with solid state control and recification systems.Would like to see one of those-but would miss the hum of the MG set and the clacking of the relays.If you can tour an elevator machine room-do so-you may be fascinated!!Sorry I drifted-another place where MG units are used.
Some of those are used as a UPS of sorts-years ago saw some Kato sets at Western Union relay site in Wash DC.Was in the coolest "art Deco" building.The units have 4 devices coupled together.--An induction motor running off the power line-A 300lb flywheel,and a DC Gen or motor-lastly a Deisel engine coupled by an overrunning clutch.the big advantage of this setup is TOTAL powerline isolation.Great for electroncs gear.No surges from the lines will get into it like with transformer-rectifier systems.Under normal use the AC induction motor powers the DC device and it charges a battery bank.the AC gen powers the equipment.If the line fails-the DC device can act as a motor and run from the batteries-again turning the AC generator and powering the equipment.As the batteries run down and if power hasn't been restored-the spinning flywheel helps start the Deisel motor and it will turn the AC gen-the DC device so it can recharge the batteries and run the equipment until the power goes back on.they said the Deisel engine could run for several days from the fuel they have.Was a very interesting setup-hadn't seen another like it.and it explains why they didn't have too many failures in their equipment.Even in this modern age MG's DO have some advantages.They could run loads that could be detrimental to SS supplies-and won't pass powerline surges.
 
I've got a Watts-Up meter. That's how I arrived at the numbers in my post on my fridge. Smarthome.com has them for $99.95. I have found them to be quite useful for measuring power consumption in appliances and for my job when troubleshooting!
 
Hi Robert

You just add the amperages.

The formula you are probably thinking of is for resistors in parallel:

total resistance is the reciprocal of the sum of the reciprocals of the individual resistors (in amps).
The reciprocal of a number is one over the number, eg reciprocal of 4 is 1/4.
the reciprocal of a fraction is to turn the fraction upside down, ie the reciprocal of 2/3 is 3/2.

Sorry but I'm not too good at typing this up, but I'll give it a go.

For example:

what is the total resistance of a 2 ohm resistor and a 4 ohm resistor in parallel?

reciprocals of 2 and 4 are 1/2 and 1/4.

add the reciprocals:
1/2 + 1/4 = 2/4 + 1/4 = 3/4

reciprocal of that is the answer:

reciprocal of 3/4 is 4/3 = 1 1/3.

So the answer is 1 1/3 ohms, or 1.33 ohms.

Chris.
 
Cool subway page!

This page is filled with THOUSANDS of pictures of the New York subway system, trains, and other lore. There's all sorts of technical information here too, including how the rail system was powered. Back in 1903 when the subway system was installed, there were a multitude of competing electrical companies (Remember Edison's DC, and Westinghouse's AC?) not to mention the fact that some neighborhoods didn't even have electricity yet. The New York subway system had to produce it's own power because of this. They chose 25hz AC just like larger electric trains were using to transmit it around the city, and converted it to DC in rotary converters to power the motors to in the trains. DC was much easier for speed control in multitude of stops of the urban system.

In the days before solid state recitifiers, AC was converted to DC using a device that looked similar to a giant generator, but what it used was a series of brushes that would "turn over" at the same frequency as the AC current, effectively converting it to DC. Take a look at the sub station pictures in the NYC subway.org site!

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nycsubway.org
 
another thought

Maybe you are thinking of power factor??

I'm not at all clear on power factor, but it plays around with the amps, meaning that amps in an AC circuit can be less than or more than you would expect.

MY very vague understanding: say a motor is 240 volt 480 watt. You would expect it to draw 2 amps.

(volts x amps = watts)

But the power factor of the motor can influence the amps draw.

I can explain it roughly if anyone would like but it can get a bit drawn out... basically it's to do with the AC volts and AC amps being out of phase, so that the simple equation doesn't work.

It becomes relevant when operating machinery on an inverter or a generator, you need to have a generator capable of more watts than the appliance to be used on it states on the name plate.

Anyway I'm getting out of my depth here...
chris.
 
Yes Robert Gizmo is correct

you just add the amperages together linearly. I was thinking of the resistances in parallel.

( Robert wanted me to post my correction so that everybody would know his hunch was correct ---OY! ThaT Boy!)

I was looking into cycloconverters last year for converting our 60 HZ into 50 HZ, they are big, expensive and ugly! I wanted to ship over a new induction cooktop from Europe BUT NOW I can just go to Sears and slap down my Sears card and BOOM BOOM DONE I've got new Induction.
 
AC to DC

"In the days before solid state recitifiers, AC was converted to DC using a device that looked similar to a giant generator, but what it used was a series of brushes that would "turn over" at the same frequency as the AC current, effectively converting it to DC."

That's the device that superseded the MG sets. They were what were refered to as rotary or "synchronus" convertors. These and MG sets were in use in San Francisco to power their streetcar and electric trolleybus system up into the 80's
 
Thanks Jon and everyone! OK now I know that when I'm running the Super Hot Cycle (or what ever I call it) I'll be using:

Unimatic Mechanism Pulsating = 6.5 Amps
Heater = 10.0 Amps
Recirculation Pump = 2.1 Amps

Total Max Amp Draw = 18.6.

Since the washer will be plugged into a 20 amp breaker that should be just fine for the 12 min wash period with occasional recirculating heated-soaks thrown in for another 8 or so minutes at 12.1 amps. The rest of the time will be a much lower AMP draw, as well as when I run warm and cool water cycles.

While the computer to run the washer will be plugged into a different outlet, I'm going to assume that computers probably draw very little amperage.
 
My Frigemore has a nameplate rating of 12A. I have run it through full cycles with a recording ammeter, and the max run amps would be about 6A with brief 9A surges.

Manufacturers are free to put whatever value they want on a nameplate. According to the National Electrical Code, 12A is the maximum load on a 15A circuit, and any appliance with a nameplate current exceeding 50% of the circuit rating needs a dedicated circuit.

Nameplate current of 12A is manufacturer warranty CYA.

Use a clamp-on ammeter with each machine. Take the highest running amperage of each, add them up, and then add 25% of the highest rating.
 

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