Hoist instalation - 3 phase to single phase

COL said:
My extension leads are made up from flex that has 2.5 mm Sq conductors which is the same size as the wiring to your GPO's. If you purchase hardware store extension leads you may suffer from voltage drop issues because most of these are either 0.75 or 1.00 mm Sq conductors.
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Correction on my extension leads the 10 amp ext leads (10 & 20 mtetres long) that I made up have 1.5 mm Sq conductors and the 15 amp ext lead has 2.5 mm Sq conductors (10 metres long)

If you would like to make your own leads up with bigger conductors than what is available from the hardware store, go to your local electrical wholesaler where you can buy flex in all sizes by the metre and also the socket and plug ends and make your own. Also you can custom make the length you require.
 
15A leads with transparent plug and socket already fitted, suitable to be tested and tagged, are builder's equipment, at the appropriate retailers.

Bunnings carries a long one.
 
COL said:
Voltage does not determine the speed of an AC electric motor, the lower the voltage the more current that will be drawn. What governs the speed of AC electric motors is number of poles in the motor and the frequency of the AC power.

My extension leads are made up from flex that has 2.5 mm Sq conductors which is the same size as the wiring to your GPO's. If you purchase hardware store extension leads you may suffer from voltage drop issues because most of these are either 0.75 or 1.00 mm Sq conductors.
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Yes I know this, voltage drop will massively increase the current. They will be slower as they will need to either turn the pump slower (gearing) or the pump must be smaller so the 2hp motor can turn it. So either way, smaller motor == slower hoist.

Possibly given the limited amount of time a hoist motor runs for, you don't burn them out running them with considerable voltage drops.... By the time the motor gets even remotely warm from the higher current, you have let the button off as the hoist is as high as it will go ?
 
Actually single phase motors that are not heavily loaded run quite happily on some reduced voltage if not excessive. That is what those 'power saving' boxes did that were the rage a while back; electronic chopping the supply a bit. It does improve the PF of the system to run a voltage that matches the load better. :rolleyes: Obviously an overload and excessive low voltage will not improve the motor performance.

But go to third world countries and see how their power is supplied with 50 houses retro supplied from one original supply and half a mile from the 'mains' sometimes!! They do work ! Who pays the bill is another question :cool:
Jaahn
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jaahn said:
Actually single phase motors that are not heavily loaded run quite happily on some reduced voltage if not excessive. That is what those 'power saving' boxes did that were the rage a while back; electronic chopping the supply a bit. It does improve the PF of the system to run a voltage that matches the load better. :rolleyes: Obviously an overload and excessive low voltage will not improve the motor performance.

But go to third world countries and see how their power is supplied with 50 houses retro supplied from one original supply and half a mile from the 'mains' sometimes!! They do work ! Who pays the bill is another question :cool:
Jaahn
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There not only power line wires, there are phone lines mixed up in that lot as well, just to make it a bit more interesting.
 
I had a look, my hoist motors are 3hp.
As previously stated they work fine on the end of a 20m, 10 amp lead.🤷‍♂️

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DoubleChevron said:
Wow .... You're running that on long 10amp leads, and your not popping the house breakers :eek:
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No, and the 20m lead is on a reel and the reel has built in circuit breakers, which don't trip either.
Keep in mind my heaviest vehicle weighs just on 2 tonne, so the pump is only working (and therefore drawing less current) at 1/2 of the hoist's 4 tonne capacity
 
Greenpeace said:
No, and the 20m lead is on a reel and the reel has built in circuit breakers, which don't trip either.
Keep in mind my heaviest vehicle weighs just on 2 tonne, so the pump is only working (and therefore drawing less current) at 1/2 of the hoist's 4 tonne capacity
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When you think about it .... a hoist never starts against a load .... unless you let the button on/off while its lifting ....
 
Greenpeace said:
I had a look, my hoist motors are 3hp.
As previously stated they work fine on the end of a 20m, 10 amp lead.🤷‍♂️

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DoubleChevron said:
Wow .... You're running that on long 10amp leads, and your not popping the house breakers :eek:
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DoubleChevron said:
When you think about it .... a hoist never starts against a load .... unless you let the button on/off while its lifting ....
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The current on the name plate is FLA so the motor is obviouly drawing less current than the protection devices or Mr Greenpeace would have tripping problems
 
COL said:
The current on the name plate is FLA so the motor is obviouly drawing less current than the protection devices or Mr Greenpeace would have tripping problems
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I've had problems with welders and compressor tripping circuit breakers. In a shed you need to change htem for the "slow" type tripping breakers, that way the startup currents of a motor starting, or striking an arc doesn't pop them. At my parents place I remember putting insulation tape onto the breaker to hold it on so I could weld and run the compressor :clown: the wiring was very beefy to the shed, but the circuit breakers weren't any good back then.
 
DoubleChevron said:
I've had problems with welders and compressor tripping circuit breakers. In a shed you need to change htem for the "slow" type tripping breakers, that way the startup currents of a motor starting, or striking an arc doesn't pop them. At my parents place I remember putting insulation tape onto the breaker to hold it on so I could weld and run the compressor :clown: the wiring was very beefy to the shed, but the circuit breakers weren't any good back then.
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Most standard breakers are "C" curve, for motor starting "D" curve are better

Here is a little explanation of the different curves for miniture cicuit breakers

 
DoubleChevron said:
The house was built in the 80's, so I don't think the circuit breakers with various curves were available at the time :confused:
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That is probably not true. These starting problems have been around since Eddison and Tesla. It would not have taken long to sort that out. SloBlow fuses were around for a long time too for the same reason. ! Three phase motors used star /delta changeover switch gear to reduce the startup surge. I had a 70HP pump motor starter fail to change over and shorted them together on startup. That blew the main building 800A fuse instead of just dimming the lights as usual. Not a popular boy but we had experienced electricians in the place to get it back on line again. And put a new starter on as well.

We think some things are new design ideas, but I worked in a Uni lab that was built new in the late '60s and the whole building was wired with inbuilt earth leakage devices in the original switch boards. Not as compact as new ones but worked just as well and were still original. They played havoc with the computers that people left switched on as was recommended 25 years ago. Hmm !

When I worked up in PNG 50 years ago we were in a big town, Madang, and I had in my workshop, a commercial welder that I had wired to run on single phase. It worked OK and could do solid welding if required. But I checked the voltage at the power point if i had to do some heavy work and put it off if the voltage was much below ~200V. It was seldom close to 240 but sometimes quite a bit over. Madang had a diesel generator in the town running during the day and a constant hydro power supply from the mountains.

When the governor fell of the hydro turbine one night the voltage got to about 400 and the cycles to about double before the local supply engineers chart recorder gave up. That blew a lot of TV s, video recorders and fridges that were on at the time. The local fridge repair man was flat out replacing the big fridge compressor motors on the wharf drive-in fridges, with diesel motors to save the frozen food in them. Home fridges were not important. The distribution system was not as protected or voltage controlled as down here.
Jaahn
 
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Back to the hoist. Although a VFD is likely able to do the job for possibly half the price of a single phase replacement pump, I would still go for the new pump as I think the VFD adds an unnecessary complexity that from some experience with these type of converters on trains, also possibly adds an unreliability.
 
These things have come a long way. I do not have one (yet) but I do follow a few of machininst channels on utube who run all sorts of things with heavy loads on chinese VFDs with absolutely no problems and they have done so for a while. In actual fact, if you had a three phase setup at home, it would be more complicated than a VFD. This does away with all the contactors and such, which would be expensive to replace if they went. The ability to run motor speed control with the VFD is an added bonus in a machine shop situation.
 
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