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Post by coalfire on Aug 17, 2008 21:02:52 GMT -5
I was wondering what hertz did they use underground in the U.K.? I know in the states we use 60hz.
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Post by dazbt on Aug 18, 2008 2:01:32 GMT -5
I was wondering what hertz did they use underground in the U.K.? I know in the states we use 60hz. UK was (or is) 50hz, which created one or two exciting moments when mining machinery manufacturers in the UK exported 50hz motors to the US ........... by mistake of course.
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Post by John on Aug 18, 2008 6:31:46 GMT -5
Just means a motor will run at a higher speed, other than that, it wouldn't do any harm to a motor or even a transformer come to that. All the Heliminers, Joy shuttle cars etc came with the US wound 60hz rated motors on that I worked with in Australia. In that case they run slower, as Australia is on the 50hz per sec standard too. Motor windings are motor windings, ie 2,4,6 or 8 pole. "Sync speed" for a two pole AC squrrel cage motor is 3000rpm, "slip speed" is 2950rpm. of 50 hz, I forget the sync and slip speed at 60hz, but will be over 3000 rpm.
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Post by dazbt on Aug 18, 2008 6:40:31 GMT -5
Just means a motor will run at a higher speed, other than that, it wouldn't do any harm to a motor or even a transformer come to that. All the Heliminers, Joy shuttle cars etc came with the US wound 60hz rated motors on that I worked with in Australia. In that case they run slower, as Australia is on the 50hz per sec standard too. Motor windings are motor windings, ie 2,4,6 or 8 pole. "Sync speed" for a two pole AC squrrel cage motor is 3000rpm, "slip speed" is 2950rpm. of 50 hz, I forget the sync and slip speed at 60hz, but will be over 3000 rpm. Lot more to think about than the effect on electric bits and bobs though John ....................... what about peripheral output speeds, hydraulic pump speeds .......... increased oil flow volumes etc?
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Post by John on Aug 18, 2008 8:39:56 GMT -5
Faster machines Daz. ;D
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Post by coalfire on Aug 18, 2008 9:14:14 GMT -5
O.K. 50hz. Most of the Motors Ive seen as in belt drives and even shuttle car motors have on their i.d. tag 50/60 hz so I don't think 10 cycles per second slower would have a great affect on performance.
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Post by John on Aug 18, 2008 9:37:47 GMT -5
O.K. 50hz. Most of the Motors Ive seen as in belt drives and even shuttle car motors have on their i.d. tag 50/60 hz so I don't think 10 cycles per second slower would have a great affect on performance. I used to know how to calculate the sync and slip speed of AC motors, time alas has got to my cranium! at 50hz, the sync speed of a 2 pole motor is 3000rpm, 4 pole motor 1500rpm, 6 pole motor is 1000 rpm, 8 pole motor 750rpm. Slip speeds are around 10% less than the sync speeds. I'd say at a rough guess sync speed of a 2 pole 60hz motor would be around 3400rpm, 4 pole 1800rpm, 6 pole 1150rpm, wouldn't be too far off.
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Post by billsharp03 on Sept 17, 2008 10:11:04 GMT -5
Frequency f = number of "pairs" of poles "p" x Speed "n" / 60
f = p x n / 60 or n = f x 60 / p or p = f x 60 / n
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Post by garryo on Mar 15, 2009 8:38:39 GMT -5
The question of electrical in frequency in mines (all types) is interesting. Generally countries that were developed or colonised by European nations including the UK use 50Hz while countries under the influence of the USA use 60Hz, however there are some notable exceptions these include Canada 60Hz, Japan which uses both 50 and 60Hz depending on which island your on, the Broken Hill area of NSW in Australia uses 40Hz as did parts of Kalgoorlie in Western Australia until the grid came along then they changed to 50Hz. Talking to an electrician from Bisbee a copper mine in Arizona who told me that some old mines in that area used 25Hz, he reckoned that if you went to a hill out of town you could see the an irritating flicker on the lights.
He also reckoned they used steam powered TVs !
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Post by tonys on Feb 18, 2011 11:36:26 GMT -5
25Hz was very common for rectification purposes up to about the 1950’s when rotary converters and mercury arc rectifiers were phased out. Just to add to the confusion much of it would be 6 phase! A 50Hz motor will run a bit hotter on 60Hz and not be as efficient.
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Post by Sam from Kent on Feb 18, 2011 12:50:59 GMT -5
Mercury Arc Rectifiers that takes me back, we had them on the pit bottom loco chargers.
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Post by John on Feb 18, 2011 15:52:53 GMT -5
Mercury Arc Rectifiers that takes me back, we had them on the pit bottom loco chargers. Joy had DC shuttle cars that used static mercury arc rectifiers too. Some DC winders also used those type of rectifiers. In both cases they had to be mounted inside steel cabinets or in rooms.
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Post by John on Feb 18, 2011 15:57:30 GMT -5
25Hz was very common for rectification purposes up to about the 1950’s when rotary converters and mercury arc rectifiers were phased out. Just to add to the confusion much of it would be 6 phase! A 50Hz motor will run a bit hotter on 60Hz and not be as efficient. They run a lot faster too Tony. All the American made machines we used in Australia used standard off the peg motors, Heliminers, Joy Miners and shuttle cars. Some things were modified to our FLP standards as US Explosion Proof doesn't measure up to either NSW or UK standards.
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Post by Sam from Kent on Feb 18, 2011 17:05:37 GMT -5
Talking about DC Winders, we had Koepe winders that were DC and I remember there was a motor at the back opf the engine room which hd to be running first before the Koepe could work as the power needed to directly start the Koepe would have drained the National Grid. Did not really understand much about it
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Post by John on Feb 18, 2011 17:22:44 GMT -5
Talking about DC Winders, we had Koepe winders that were DC and I remember there was a motor at the back opf the engine room which hd to be running first before the Koepe could work as the power needed to directly start the Koepe would have drained the National Grid. Did not really understand much about it It was a motor generator set Sam, called the Ward-Leonard system. You have a three phase motor driving a DC generator that is used to drive the winding engine. The driver controls how much field current is applied to the generator fields to control the winder speed. It is much more efficient for speed control than a slip ring winding engine motor. Now days DC winders are the norm with thyristor electronic controls instead of the old Ward Leonard system.
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Post by Sam from Kent on Feb 18, 2011 17:30:10 GMT -5
I vaguley remember the name Ward Leonard. I remember it had a big tank full of water and you wound a handle which lowered fins into the water to alter the resistence on start. We also used these on the pit bottom pumps. We had 1100 H.P. motors on the pumps
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Post by John on Feb 18, 2011 17:45:26 GMT -5
I vaguley remember the name Ward Leonard. I remember it had a big tank full of water and you wound a handle which lowered fins into the water to alter the resistence on start. We also used these on the pit bottom pumps. We had 1100 H.P. motors on the pumps Wrong system Sam, slip ring motors use resistance inserted into the rotor windings to start them up slowly and keep starting current down. Most use switched "stepped" dry type resistors, like conveyors or large compressors. The Cable Belt we had at Clifton used stepped resistor banks. When they used slip ring motors for winders, they used a liquid and wound the blades of the starter in when the winder was initiated, the liquid was called an electrolyte and had some sort of alkaline in it. Been too long since I worked on those type of starters/controllers, but I think it was soda ash. The more the blades entered the electrolyte the less resistance the faster the motor operated. Of course on winders the blades were wound in and out by an electric motor controlled by the drivers control lever. Ward-Leonard system is a three phase motor directly mechanically coupled to a large DC generator whose output is coupled through a large DC contactor to the winding engine. To control speed, the drivers controller is coupled to the field windings of the generator and applies excitation to them to form a magnetic field. The more excitation, the more power, the faster the winder operated. Very simple but pretty inefficient by todays standards.
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Post by Sam from Kent on Feb 18, 2011 18:23:07 GMT -5
From what I remember, there was no connection between the controils from the winder to the water tank. Whn the motor was started up, the fins were out of the water and the fins were wound into the water by a handle fitted to the resistance unit, then the motor ran at a constant speeed when it was running. Never did understand how the winder was controlled from that
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ken
Trainee
Posts: 46
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Post by ken on Feb 20, 2011 2:11:04 GMT -5
The starter was just used to run up the motor generator set. Winding control was part of the Ward Leonard system. where a small change in field current of generator caused a large change output. Some of the liquid starters on the surface had copper contacts which made when the dippers were at the bottom which made effectively a zero resistance in the slip ring circuit. At Easington they had Ward Leonard Illigner systems which used a synchronous motor for the generator set. The MG set had two generators and the winding engine two motors. These were Met/Vic machines. Rarely gave any trouble. they had massive commutators on them I suppose they could not make machines like that now. Neither the skills nor equipment. Ken
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Post by John on Feb 20, 2011 8:06:33 GMT -5
Ideal place to have a synchronous motor Ken, plus they like steady loads!
Never thought about the skills of making DC motors must now be gone. When I left the board in 68, I went to work for J Jones Rewinds as an electrical fitter. They were one of two premier rewind firms who did a lot of NCB work. The other was Wilson Ford Rewinds, I spent a couple of years with them too overhauling both rotating and static machines, switchgear etc. We had some very highly skilled armature winders at both companies. It was a treat to watch how a very large armature was wound, a job a machine cannot yet do.
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Post by tonys on Feb 22, 2011 5:57:55 GMT -5
There was a Ward Leonard system that used a slip ring motor to drive the generator with a large flywheel placed in between.
The system I was reading about the flywheel was 11 tons. Once the motor was up to speed the grids in the liquid starter were backed off slightly allowing the motor speed to drop under load.
When the winder started the flywheel gave up energy to assist the motor to absorb the peak currents. On stopping the winder used regenerative braking and the flywheel absorbed the energy. If you drive a motor it will generate.
This was used where the supply was a bit weak.
I’ll try and find the details of the system I was reading about, it came from an accident enquiry report about an over wind.
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Post by tonys on Feb 22, 2011 7:31:43 GMT -5
Found it!
General Electric
Winding motor 1,200/2,040 hp 53.7 rpm 425V 2260/4000A 900/1700 KW 425V generator Flywheel 11¼ tons Motor 900/1800 hp 3.3KV slip-ring 1000/820 rpm Depending on load Combined liquid starter and slip regulator
As you can see the generator motor output is lower than the winding motor output, the short fall being made up by the flywheel
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Post by John on Feb 22, 2011 13:24:37 GMT -5
How long ago was that Tony?? As it seems a little "ancient" by that I mean, doesn't sound like an NCB setup.
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Post by tonys on Feb 22, 2011 16:35:23 GMT -5
Installed 1929
You say you worked for Wilson Ford. I met Blaze Ford when we had problems at Stanton Iron Works with a 2000hp motor. He was helpful, but it took me another 6 weeks to get to the bottom of the problem.
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Post by John on Feb 22, 2011 17:03:45 GMT -5
That explains it, pre electrical grid, would have been state of the art back then to cope with power line "sag".
I think the majority of mid 60's NCB pits were supplied with two main HT feeders, one in use all the time, second as back up should the first fail.
I've worked on some old equipment in my time, but I think the oldest gear was some oil cooled transformers we had when I worked in Australia. My district transformers had slate insulators on the 400 volt circuit breakers!!! They must have dated back to the 1930's or earlier, surprising they were still in good working order after all those years.
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Post by John on Feb 22, 2011 17:04:54 GMT -5
That explains it, pre electrical grid, would have been state of the art back then to cope with power line "sag".
I think the majority of mid 60's NCB pits were supplied with two main HT feeders, one in use all the time, second as back up should the first fail.
I've worked on some old equipment in my time, but I think the oldest gear was some oil cooled transformers we had when I worked in Australia. My district transformers had slate insulators on the 400 volt circuit breakers!!! They must have dated back to the 1930's or earlier, surprising they were still in good working order after all those years.
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Post by Sam from Kent on Feb 22, 2011 17:47:07 GMT -5
I think that the 2 HT feeders were in use all the time with connectors in the main surface substation and pit bottom sub station capable of connecting accross, but in normal working they were both left open
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Post by John on Feb 22, 2011 18:21:53 GMT -5
But what your supply was and what you used was far lower Sam. probably 130Kv plus transformed down in the main switch yard to either 3.3Kv or 6.6Kv in latter years.
Last pit I worked at was supplied with 66Kv to our switchyard and transformed down to 11Kv for the underground feeder, which fed our main breakers underground, then sent to the various districts and transformers. We used 415v conveyor drives, 1.1kv equipment on the longwall, and development was 1kv continuous miners and 415volt shuttlecars.
The drift winch was DC thyristor controlled at around 400 volts radio controlled.
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Post by Sam from Kent on Feb 23, 2011 4:24:11 GMT -5
Yes it was transmitted at 3.3kV into the districts and then stepped down to 550 v at the face (but latterly it was down to 1100v at the face)
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Post by John on Feb 23, 2011 7:50:16 GMT -5
I think the newer bigger horsepower faces are at 3.3Kv now.
I know way back, we had 3.3Kv heliminers and the boss wanted to go the whole hog and have 6.6Kv miners, Inspector wouldn't be in on it and cited our record for "pulled" cable ends. They were controlled from Belmos KFG 3.3Kv "GEB's"
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