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New or old style 3 phase motors?

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Andrew Tinsley06/06/2020 10:52:53
1109 forum posts

I have some unused Brook Crompton 3 phase motors still in their original boxes. They are probably 40 years old.

For inverter use, I seem to remember that these old style motors are not the best choice. Lower maximum operating temperature and prone to heating with the HF in the inverter supply. Modern motors are better equipped to cope so I am told.

Now I need a motor to power some kit and once installed, it will be very difficult to access. Do I buy a cheap TEC motor or use one of the Brook Crompton motors?

Which is more reliable on inverter power? Indeed are the cheaper TEC motors a good choice? They are Chinese made but with an English sales company

Thanks,

Andrew.

Emgee06/06/2020 11:12:16
1485 forum posts
217 photos

Andrew

If the Brook motors are dual voltage so can be connected in Delta for 220v working my choice would be use one, if it doesn't work as needed you will have lost nothing as the newly purchased VFD can be used on another motor of the same size.

Emgee

John Haine06/06/2020 11:16:47
3075 forum posts
162 photos

I use an old Brook 3 phase motor on my VMB with an inverter and it's just fine! Came star connected but all windings accessible through the terminals so delta connection was easy. I run it at up to 2100 revs (it's 4-pole @ 75 Hz) with no problems.

Clive Foster06/06/2020 11:45:28
2200 forum posts
73 photos

Andrew

In practical world probably nothing in it. Old motor issues with VFD's are more to do with thermal degradation of the insulation over many years of use than intrinsic engineering.

So long as you are sensible when it comes to speed range and loading I can't see any problems. Stick with the conservative ± 1/3 rd of nominal speed range, i.e. 2:1 variation near enough, and all should be fine. Especially if you use a decent brand self tuning vector drive inverter.

There are many parameters involved in the design of an electric motor with considerable scope for tweaking the performance and manufacturing cost.

TEC motors will be built to a decent, but economy range, industrial standard so they will be fairly straightforward design. Modern insulation will have higher rated operating temperature but its likely that design compromises for lower price point will lead to the innards running bit hotter than the old style Brook.

Motors specifically designed for VFD use are very different, more sophisticated, animals and correspondingly expensive. Mostly "inverter duty" just means there are some specifications for preferred speed range before your run into delivered power issues. 75 Hz maximum constant power speed is a common specification for such.

Clive

Andrew Tinsley06/06/2020 11:46:56
1109 forum posts

Thanks you both for that information, it looks as though the doomsayers re older motors may be too pessimistic. The motors are able to be connected in Delta, otherwise, I would not have asked!

Andrew.

mgnbuk06/06/2020 11:54:25
763 forum posts
60 photos

Modern motors have a much reduced clearance between the rotor & stator compared to older designs.

My previous employer built a number of special purpose CNC lathes for Brook Motors Honley plant (which produced the small motors), the specific aim of which was to machine the end plate locating spigots on the stator casing to be more accurately located with respect to the bore through the stator laminations to allow the reduction of the rotor clearance. The reduced clearance was apparently required to improve effieciency and give better operation with inverters. This was probably about 20 years ago so not really new, but newer than the OPs boxed old stock.

Incidently, according the published Brook information, motors that have been stored for more than (IIRC) a couple of years should have their bearings replaced before being put into operation - vibrations from the environment apparently cause the bearings to Brinell where the static balls have been sat & give noisey running and premature failure if not replaced before being put into service.

All of the Brook Motors manufacturing plants (the main plant was in Huddersfield, with smaller plants in Honley & Barnsley) closed over 10 years ago,

Nigel B.

Clive Foster06/06/2020 12:32:37
2200 forum posts
73 photos

As mgnbuk says there has been a steady evolution in motor design and build practice in the search for improved efficiency, lighter weight and lower cost fora given performance.

Little of which is greatly relevant to the fundamental operation of an ordinary type of motor. The modern one may be little more efficient but the old style one goes round just has well. But the electric meter may run faster.

One common disadvantage of the modern style build "energy star " et al motors in practice seems to be a shorter torque curve and lower overload capability. Decent old style motors seem to hang on much better if inadvertently overloaded. They slow down but keep turning whilst energy star et al breeds tend to stall out after significantly smaller speed drops. No doubt a complex matter of detail design, build standards and materials availability.

There is no doubt that a modern motor goes a lot better with a self tuning vector drive type VFD than with a more basic type. Old style still likes a vector type but the difference seems not to be so marked.

Clive

SillyOldDuffer06/06/2020 12:33:14
5746 forum posts
1211 photos
Posted by Clive Foster on 06/06/2020 11:45:28:

Andrew

In practical world probably nothing in it. Old motor issues with VFD's are more to do with thermal degradation of the insulation over many years of use than intrinsic engineering.

So long as you are sensible when it comes to speed range and loading I can't see any problems...

Clive

I looked into this and found there's another issue with old motors. It's that the rotor earths through the bearings. Doesn't matter with smooth mains 3-phase, but spiky VFD volts causes tiny sparks that gradually eat the bearings. The same spikes are bad for old-fashioned insulation, specially if the motor gets hot.

The bearing problem was fixed by better earthing circa 1970, but old insulation can't be improved and gets worse with age and poor storage. The best old motors are inferior to well made modern ones.

These problems reduce the working life of old motors, but it only really shows when worked hard for long periods. As home workshop motors have comparatively easy lives I'd happily use an old motor in good nick. Might not be best practice but there's a good chance an old motor will last longer than me!

Dave

 

 

Edited By SillyOldDuffer on 06/06/2020 12:34:22

Pete Rimmer06/06/2020 13:47:32
707 forum posts
49 photos
Posted by Andrew Tinsley on 06/06/2020 10:52:53:

I have some unused Brook Crompton 3 phase motors still in their original boxes. They are probably 40 years old.

For inverter use, I seem to remember that these old style motors are not the best choice. Lower maximum operating temperature and prone to heating with the HF in the inverter supply. Modern motors are better equipped to cope so I am told.

Now I need a motor to power some kit and once installed, it will be very difficult to access. Do I buy a cheap TEC motor or use one of the Brook Crompton motors?

Which is more reliable on inverter power? Indeed are the cheaper TEC motors a good choice? They are Chinese made but with an English sales company

Thanks,

Andrew.

What size are your motors Andrew? I am looking for something suitable for my grinder, 1/2 to 3/4hp 3 phase and a NOS Brook Crompton would be ideal. If you had one you would sell I'dl abandon the single phase motor currently fitted in favour of a 3 phase motor and fit a VFD.

old mart06/06/2020 13:58:19
1740 forum posts
138 photos

I suppose it depends how wide a speed range you intend to run them at. 30-70Hz would be a fairly safe range, but very slow and the cooling fan does not work very well. There are supplementary fan units which are independently powered, but they are expensive. They would need to be convertible to delta to suit the most common 230V VFD's. The modern motors have different dimensions to the old ones. I had to change the mounts and the pulley bore for the new one I recently fitted.

Dave Halford06/06/2020 14:03:28
742 forum posts
6 photos

The only issue might be a new 1hp motor will use less current than an old one so you might need a 1.5hp VFD to run it.

Mike Poole06/06/2020 14:10:55
avatar
2572 forum posts
60 photos

Inverters have improved the waveform presented to the motors, some early inverters had very poor waveforms and produced a lot of noise and heat with the harmonics delivered to the motor. A decent modern inverter will give a motor a much easier time. Unless you have a use for the motors that you have I would run one and see if it runs happily. Inverters in the form of a UPS or power conditioner can be used to give a cleaner supply than the mains in some difficult environments.

Mike

Martin 10006/06/2020 15:32:42
262 forum posts
6 photos
Posted by mgnbuk on 06/06/2020 11:54:25:

All of the Brook Motors manufacturing plants (the main plant was in Huddersfield, with smaller plants in Honley & Barnsley) closed over 10 years ago,

Do you know where they are manufactured now?

mgnbuk06/06/2020 15:54:31
763 forum posts
60 photos

Do you know where they are manufactured now?

Not sure. They are owned by a Far Eastern company now & as far as I know the Huddersfield site is just a warehouse. Some of the manufacturing equipment was shipped out to Poland & there was also an Indian manufacturing plant.

A late friend of mine worked there from leaving school to being made redundant after (IIRC) 43 years when the die casting facility was moved to Poland. He had held various positions (including a long stint as an instructor in the in-house apprentice training school), but the last was as a manager in the die casting shop. His son & daughter both worked there as well, his son being a toolmaker who worked on producing the die casting tools for the Indian operation. This was supposedly to supply motors solely to the Far Eastern markets & not for import to the UK, but I don't think that stance lasted long.

The Brook companies had been owned by Hawker Siddeley for many years, but IIRC they were subject to a hostile takeover & it all went downhill from there - in the end the companies were sold to the Far Eastern owner (another motor manufacturer) for some nominal figure plus debts. IIRC the Huddersfield plant once employed around 700 people, but by the time my friend's daughter left there were only around 25.

Nigel B

Martin 10006/06/2020 19:08:40
262 forum posts
6 photos

Thanks for that Nigel.

I had thought they were still 'British' and with a pending purchase I would have chosen them over some 'unknown' brand. Strangely their offerings look very much like those of ABB

I have several 'Brook Crompton' motors dating up to the mid 1980's on various,bits of workshop machinery a few with Huddersfield on the rating plates and a few with Doncaster.

I turned up this about Brook Motors and Crompton Parkinson and their other factory that produced motors in Doncaster.

Era ends as Crompton Electric Motors prepares to close

1st September 2008

The company can trace its history back to Colonel Rookes Crompton’s original DC motors business formed in 1878, and the foundation of Brook Motors in 1904. In 1927, RE Crompton & Co merged with F & AE Parkinson to form Crompton Parkinson. which opened the Doncaster plant in 1946 to produce motors and light fittings. In 1967, Crompton Parkinson was acquired by Hawker Siddeley, which bought Brook Motors three years later, merging the businesses to form Brook Crompton Parkinson Motors in 1974.

In 1990, Hawker Siddeley added the GEC Electromotors small motors business to its portfolio, but the following year Hawker was itself acquired by BTR. In 1999, BTR merged its operations with Siebe to form Invensys and three years later the small motors business was sold to Tyco Electronics.

Tyco invested around £500,000 to expand into the DC motors business and to develop matching gearboxes. In 2005, it renamed the business Crompton Electric Motors. The company has continued to use the Crompton name under licence from Brook Crompton.

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