Motors

[Knobhead]

The ones we had for the ID fans were about 20 years old. I had one of the thyristor packs fail, I was near it when it went. When we opened the panel we were expecting a charred mess but no the only thing was a blown fuse. That is what I’d heard. Changed the fuse and it’s thyristor pack and it ran perfectly afterwards.

The fuse went in spectacular style, the thyristor tested perfectly?

View attachment 14226View attachment 14227

 

[DurhamSparky]

Hi tony, on one of our sites we are running the supply fans for cooling at 120% and 45% above the working Limit of the supply fuses and thyristor. Every 2-3 months we have to replace the lot. Occasionally the supply cable melts and that gets changed as well.... Oh and the cab door is fully open as to keep temp down

Madness but cheaper than upgrading the whole system.......

 

[Knobhead]

I'll bet it's not that cheap either.

 

[DurhamSparky]

Yes, costs us approx 200-300 for replacement parts, (fuses we change more regular weekly)

Upgrade the system for additional capacity and improved running efficiency = £5.4million

We are upgrading in the next 12 months as part of the phase 3 improvements which will see data storage at the site increased by 40% and power increase from grid upped to silly levels.

Nedl currently pulling new 300mm Hv supply cables in directly from the sub station 15 miles away. With a secondary supply coming in from another site. That's costing £15million alone.

So until then we have to live with repairs!!! Lol

 

[Knobhead]

Kramer speed control

This is a somewhat bizarre method of controlling the speed of a slip-ring motor. I’ve worked on them up to 2500HP, RoB2, has I think worked on bigger drives.

View attachment 14587
The motor starts as a normal motor using the liquid starter. Contactors 1 and 3 close and the motor runs up to speed using the liquid starter. Once at full speed the shorting contactor 2 closes.
The motor can then work like this or the speed can be controlled. For speed control contactor 4 closes and the inverter synchronises to the transformer. Contactor 2 and 3 then open, all the current from the slip-rings is then fed via the inverter and transformer to the incoming supply. Slowing the speed raises the ring voltage at the same time reducing the current. Reducing the current allows the slip of the motor to increase thus slowing it. This excess power feeds back in to the supply. I’ve watched one of the 2500HP (1865KW) feeding back up to 750KW in to the system.
The transformer has a six phase primary Star and Delta with a delta secondary DSd.
These are now superceded by MV VSD’s. these come with their own headaches such as 11KV water cooled inverters.

View attachment 14588View attachment 14589
This fuse was out of a Kramer drive. It near gave me heart failure when it blew, but the drive just carried on as if nothing had happened!

 

[Bobster]

There now all nicely packed into one plug and play 27tonne inverter. No liquid starter needed. Massive air conditioning units needed fitting though it chucked some heat out.

Ill try and dig some photos of it, not sure if I ever took any.

When using them to power more than one drive, the regenerated power is shared along a dc bus, because
It runs at near unity power factor, it's pretty efficient.

 

[Knobhead]

There now all nicely packed into one plug and play 27tonne inverter.

The Chinese will soon clone them, all packaged in a suitcase.

 

[Bobster]

So a little on DC drives for a wet Sunday afternoon.

[TABLE="width: 563"]
[TR]
[TD]Shunt-Wound Motors - This type of motor runs practically constant speed, regardless of the load. It is the type generally used in commercial practice and is usually recommended where starting conditions are not usually severs. Speed of the shunt-wound motors may be regulated in two ways: first, by inserting resistance in series with the armature, thus decreasing speed: and second, by inserting resistance in the field circuit, the speed will vary with each change in load: in the latter, the speeds is practically constant for any setting of the controller. This latter is the most generally used for adjustable-speed service, as in the case of machine tools.

The shunt motor is probably the most common dc motor used in industry today. Components of the shunt motor are the armature, labeled A1 and A2, and the field, labeled F1 and F2. The coils in the shunt field are composed of many turns of small wire, resulting in low shunt field current and moderate armature current. This motor provides starting torque that varies with the load applied and good speed regulation by controlling the shunt field voltage. If the shunt motor loses it’s field it will accelerate slightly until CEMF rises to a value sufficient to shut off the torque producing current. In other words, the shunt motor will not destroy itself if it loses its field, but it won’t have the torque required to do the job it was designed for.
Some of the common uses of the shunt motor are machine shop lathes, and industry process lines where speed and tension control are critical.

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Series-Wound DC Motors - This type of motor speed varies automatically with the load, increasing as the load decreases. Use of series motor is generally limited to case where a heavy power demand is necessary to bring the machine up to speed, as in the case of certain elevator and hoist installations, for steelcars, etc. Series-wound motors should never be used where the motor cab be started without load, since they will race to a dangerous degree.

Components of a series motor include the armature, labeled A1 and A2, and the field, S1 and S2. The same current is impressed upon the armature and the series field. The coils in the series field are made of a few turns of large gauge wire, to facilitate large current flow. This provides high starting torque, approximately 2 ¼ times the rated load torque. Series motor armatures are usually lap wound. Lap windings are good for high current, low voltage applications because they have additional parallel paths for current flow. Series motors have very poor speed control, running slowly with heavy loads and quickly with light loads. A series motor should never drive machines with a belt. If the belt breaks, the load would be removed and cause the motor to over speed and destroy itself in a matter of seconds.
Common uses of the series motor include crane hoists, where large heavy loads will be raised and lowered and bridge and trolley drives on large overhead cranes. The series motor provides the starting torque required for moving large loads. Traction motors used to drive trains are series motors that provide the required torque and horsepower to get massive amounts of weight moving

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Compound-Wound DC Motors - A combination of the shunt wound and series wound types combines the characteristics of both. Characteristics may be varied by varying the combination of the two windings. These motors are generally used where severe starting conditions are met and constant speed is required at the same time

When comparing the advantages of the series and shunt motors, the series motor has greater torque capabilities while the shunt motor has more constant and controllable speed over various loads. These two desirable characteristics can be found in the same motor by placing both a series field and shunt field winding on the same pole. Thus, we have the compound motor.
The compound motor responds better to heavy load changes than a shunt motor because of the increased current through the series field coils. This boosts the field strength, providing added torque and speeds.
If a shunt coil is added to a series motor at light loads (when a series motor tends to over speed) the added shunt field flux limits the top speed, eliminating self-destruction.
Common uses of the compound motor include elevators, air compressors, conveyors, presses and shears. Compound motors can be operated as shunt motors by disconnecting the series field. Many manufacturing process lines are designed this way. The reason being that, most off the shelf motors are compound motors, and the series field can always be connected later to provide additional torque, if needed.
Compound motors can be connected two ways, cumulatively and differentially. When connected cumulatively, the series field is connected to aid the shunt field, providing faster response than a straight shunt motor. When connected differentially, the series field opposes the shunt field. Differentially connected compound motors are sometimes referred to as “suicide motors,” because of their penchant for self destruction. If perhaps, the shunt field circuit were to suddenly open during loading, the series field would then assume control and the polarity of all fields would reverse. This results in the motor stopping, and then restarting in the opposite direction. It then operates as an unloaded series motor and will destroy itself. Differentially connected motors can also start in the opposite direction if the load is too heavy. Therefore, it is seldom used in industry[/TD]
[/TR]
[/TABLE]

 

[Silly Sausage]

What has happened here?
All the pictures and diagrams have gone! :-(

 

[Sparky Ninja]

What has happened here?
All the pictures and diagrams have gone! :-(

cause and effect mate.

 

[Silly Sausage]

cause and effect mate.

Really! :speechless:

Well bugger me!

 

[Geordie Spark]

Really! :speechless:

Well bugger me!

I'm sure Harness69 will oblige ....... if you ask nicely

 

[Silly Sausage]

Ferk Off!

Anyway, I think it's no more, probably permanently shafted on a 20 foot scaff pole.

 

[Geordie Spark]

Ferk Off!

Anyway, I think it's no more, probably permanently shafted on a 20 foot scaff pole.

Well we can always hope ....... :devil:

 

[Knobhead]

Designs, Patents and Copyright Act 1988.

The simple reason all drawings have been removed is purely down to the current situation on certain boards. Any drawings I post in future on any board (both UK or international) will be held on a hosting site. This is to protect my rights under the Designs, Patents and Copyright Act 1988.
To restrict access to copyright material both written and illustrative infringes both the Designs, Patents and Copyright Act 1988 and the Data Protection Act.