Member postings for Clive Steer

I think I did say that the PAT test does NOT cover the tests needed to prove product electrical safety compliance.

It's been some time (13 years) since I last had to read and design products to comply with the Machinery and EMC directives but as far as I recollect IEC 61010 was to do with product electrical safety. The specifications may not mention earthing per se as this is only one way of achieving electrical safety. A double insulated device doesn't need an earth and a lathe may be classed as such if the motor and associated electrical system are installed in such a way that a failure of insulation or clearance will not result in an accessible conductive part becoming live. However when the lathe is installed in a factory or workshop another assessment is needed to ensure the product remains safe to use and earthing may be needed and two earths one of which can be visually inspected helps maintain safety compliance which may be defined by the Factory Act or other electrical safety requirements.

Clive S

To cover another point that was made regarding earth wires. Earth wires shouldn't carry anything other than fault currents and then only for the time needed for supply disconnection. If it is then it is a supply connection intended or otherwise. There are complications where a supply wire is bonded to an earth wire eg neutral to earth and early electrical standards or lack of standards caused dangerous situations. This could arise if one bit of kit was connected to another bit of kit made to a different standard. All wires, just like any aircraft propeller, should be treated as live until proven otherwise and electrocution isn't an appropriate method of testing.

Clive S

The requirement for two earth usually applies for industrial equipment and a lathe, although being used in a domestic environment, is still industrial. A usual the requirements are written in such a way that they do not necessarily describe the solution just the needed requirement. So the requirement may specify the need for a "fault disconnection device" known to me and others as a fuse. If you look on the back of some equipment you'll see the the normal IEC 3 pin connector for the mains power and close by a threaded post with a earth symbol next to it. This is for the second earth wire. A lot of domestic devices don't need a second earth because there are no exposed conductive parts that can be touched by a "Standard finger".

The second earth on a industrial machine may be via the metal conduit the supply comes through and if there is a flexible section there should be a seperate earth wire wrapped around the flex tube in case it gets stretched and becomes disconnected.

The normal PAT test does not cover the electrical tests needed to prove product compliance.

Check out IEC 61010 and IEC 60204-1 if you can't get to sleep at night.

Clive S

Maybe electronics equipment is becoming too reliable and the tin whiskers helps give them a finite life so you can buy the next model.

Clive S

There are several different ways of providing emergency stop depending on the nature of the emergency.

If there is a mechanical/operator entanglement emergency the machine may need to be stopped as quickly as possible which may require a mechanical brake or an inverter to apply regenerative braking. Having an eStop that removes power from the inverter prevents regenerative braking.

However if there is an electrical emergency such as fire or electrocution, then an eStop that removes all power, is appropriate.

An inverter eStop will trip the inverter and will require power to be cycled to reset it or a dedicated input used as a reset.

In a complex machine a risk assessment and FMEA will govern what/who handles an emergency stop and how it is handled.

Modern electrical safety requirements requires any device made of a conductive material (metal) to be earthed whether there is electrical power connected to the device or not. The thinking here is that the device could become live if a device with an undetected fault came into contact with it. So for instance a steel central heating radiator in your house is required to be earthed. This is normally provided by the copper pipes but with the increasing use of plastic pipe and fittings earth continuity may be lost and supplementary earthing is needed.

An electrical machine such as a lathe would normally have two independent earth connections with one that can be visually checked for presence. The thinking here is that a single failure, ie broken earth wire, should not cause a machine to become unsafe and no special equipment is needed.

Domestic dwellings now have to have a residual current trip device (earth leakage trip) but there are many that have not been upgraded so good earthing practice is always wise and you can't have too many belts and braces.

Clive S

I have just concluded my experiment which proves my thinking was incorrect and winding "polarity" is important. With one phase winding reversed the motor vibrated and had very low torque.

I will give myself a serious talking to.

So Colin, as has already been said by others, the wires joined to form the "star" point can be regarded as starts.

Clive S

I believe that a standard 3 phase motor is a symmetrical machine so winding "polarity" shouldn't be important but I stand to be corrected.

However for a 2 speed 3 phase motor, using a Dahlander winding configuration, winding "polarity" is important as the flux coupling from each winding interact to change the stator pole pattern from 2 pole (Hi Speed) to 4 pole (Lo speed). The special winding arrangement is also the reason why a Hi Volts 2 speed motor cannot be changed to a Lo Volt motor in the same way Star can change to Delta.

I will experiment with a 3 phase motor I have to check if my thinking is wrong.

Clive S

Colin

Your list of steps to take is correct. Probably the most difficult task will be doing the retying to hold the wires in place as threading through a cord can be tricky. However if you just snip the original loops but initially leave them in place and you may be able to use them to pull new thread through. However you can use small thin cable ties instead.

From what I can see from your pictures you will probably find three wires, sleeved in yellow, emerging from the coils on the outer rim of the windings. Another three wires will emerge from their respective windings nearer the centre.

It doesn't really matter what are start and finishes of the windings provided you can identify each of the three individual windings so you can connect them in true delta configuration. The marking is only required to ensure the motor will rotate in the right direction when connected to a 3 phase supply but if it doesn't swapping any two phase wires will make it rotate in the opposite direction.

If you'd like to PM me I'll give you my phone number and I can talk you through the process as you do it. If you can make a FaceTime or Zoom call I can watch you do it and comment.

Clive S

Hi Colin

I think I can see 6 tails from the windings sleeved in yellow. Three, will be combined to form the star point but will have no other connection. The other ends will be connected to each of the red wires.

The down side is that to convert you have to cut the tie threads find the start point and connect a wire to each of the wires and then retie. You can use soft solder for the joins but it is better to use crimps as these won't let go if the motor or wire get overheated on overload. Just copy how the current joints are made and extra insulation sleeving is applied.

Clive S

I don't think any of the people running cannabis farms have any problems with meters, smart or otherwise.

However, if everyone had a smart meter and the electricity suppliers monitor the power being supplied by each sub-station/transformer they would easily be able to narrow down where the "leak" was. This applies to gas and water as well but I'm not so sure the water companies want to know where their leaks are.

Also be wary of the situation with TV licences in that those addresses without a licence became the target of suspicion.

I'm not sure now who the "supplier" is. Is it the company I pay money to for my power and do they "own" the smart meter and have control over it. If I move "suppliers" do they then "own" the meter. Also if they cut me off they won't receive the benefit of my solar panel power. Maybe they'll only cut me off on cloudy days.

CS

I'm not sure why people appear to be so resistant to the fitting of a smart meter given that they are not that smart but only allows more detailed information about your energy usage and the more good information you have the better you are able to make good decisions. The user can use the info to reduce their bills, if they have a mind to, and the supplier gets a better understanding of domestic usage. They could provide more flexible charging providing finer granularity and hopefully persuade people to spread the load more evenly which helps both user and supplier.

CS

With electricity prices are going up will the energy companies pay more for the electricity generated by solar panels. I think not and I think the same pricing policy as vehicle fuel will apply for other energy sources in as much that when crude goes up the price at the pump reflects this immediately but when crude comes down the same doesn't happen.

I think the term "Smart meter" is typical 1984 speak and when 2G/3G gets turned off they revert to manual mode.

It'll be nice to get back to the good old days when you had to break the ice on the toilet first thing in the morning.

CS

I concur with Howard .

Iron oxide (rust) is very hard and an abrasive in itself (rouge) so more damage can be done to the slip gauge if removal is done mechanically. So use phosphoric acid or another mild acid to soften the rust and scrub with a tooth brush. When hardened steel, and I believe slip gauges are, become rusty the rust may form along weakness lines in the crystal lattice so appears as strands or small pockets. Once the rust is softened with the acid and scrubbed check, under a microscope, to see if the rust has gone and if not gently use a pointed stylus to pick it out. Better to use several short acid/scrub sessions than leaving them in the acid too long. Also make sure you dry the gauges after each acid/scrub/rinse session as a film of rust can quickly form. Be sure to clean the slip gauges in isopropyl alcohol or another degreasing fluid as the rust may have formed under the layer of protective oil the gauges should have on them. The oil can soak into the rust making the action of the acid less effective. Cleaning the gauges in a ultrasonic tank may also help liberate stubborn rust but check this on the worst affect gauge before doing it to the rest.

All said and done slip gauges are essential for the Gods of Precision but not so much for us mortals of imprecision.

Clive

Colin

If the motor is wired for star and cannot be altered easily it will run on Lo Volts 3 phase but develop a quarter of the torque but probably sufficient for testing. The speed will be right whatever voltage the motor is feed with except for a more slip at the reduced torque.

Clive

Colin

Although more modern motors have 6 terminals and usually brass jumper link some early motors had just 4 terminals. Each of the wires from the windings, there should be 6 in total, will be identified either by colour or some other form of marking. Note down what the connections are at the moment for use later.

For 380/420V (Hi Volts star connection) three wire from the winding would be connected to one terminal to form the star point and each of the other ends of the 3 windings would be connect to a single terminal to which the three phase supply is connected. This is most likely the connection arrangement you have at the moment.

For 220/240V (Lo Volts Delta connection) operation the three windings are connected effectively in a ring. So the end of one winding is connected to the start of the next winding.

However how does one know what are the start and finish of each winding if the motor doesn't have a circuit diagram on the terminal box cover. The three wires connected to the common star point , if connected for Hi Volts, are likely to be the finish of each winding.

So begin by isolating each wire from the star point and then use an ohm meter to find the match start of each winding and note the colour.

Clive Steer

Over several nights my wife and I would hear something large scrabbling about in the house and closer inspection in some hard to get to places revealed rat dropping. I did some research about rats and getting rid of them but didn't want to use traps or poison. The research suggested that rats would go out during the day to scavenge for food and then find somewhere warm and safe during the night. The only thing I needed to do was find out how they were getting into the house and particularly the wall cavity. It turns out that the hole, through which our power cable enters the house had been uncovered when our front drive was relaid and not closed afterwards. We closed this entry point during the day and have never had the rats return.

Clive

If anyone has motor/electrics problems on an old machine and especially those with a two speed motor I would recommend buying a modern 240V 3 phase induction motor and a VFD. However, having said that, I believe that there are some 3kW brushless DC motors available that have superior driving capabilities than an induction motor when operating at slow speed. Even if these motors are optimistically rated ie described as their peak rating rather than their continuous rating they are seriously powerful. Also, having permanent magnet rotors, rotor heating when operating at low speed and high torque isn't as big a problem as it is with an induction motor. Most induction motors are fully enclosed to prevent the spread of fire in the event of a motor overload and rely entirely on a shaft mounted cooling fan blowing air over external cooling fins. However at low speeds this would provide far less cooling so for continuous use at low speed a fixed speed electric fan should be used to cool the motor or use a much larger motor and use the VFD to limit the power it can provide.

Since the electronics of a VFD and a BLDC motor controller are virtually identical only the extra cost of a BLDC motor may be an issue. However their higher efficiency and their capability to produce high torque at low speed , I believe, gives the BLDC motor the edge. From an historical perspective DC motors have always been the favourite for traction applications and brushless motors will hasten their return.

Usually there is also a glass scale on the read head that produces a interference pattern with the main glass scale and I've have one of these becoming detached. I'm not sure you'll see the LED's light up as they are normally Infra-red but not sure what modern scales may use.

Clive

Hi Dell

The BLDC motor I use for powering a Geneva or WW watchmakers lathe is a DB59S0124035-A bought from Farnell stock number 250 7574 . The power supply, also bought from Farnell, is a 100 W 24V enclosed type stock number 379 0321 you will also need a 10k ohm potentiometer to provide the speed demand input to the BLDC controller.

The BLDC controller I've used is from eBay type ZS-X11H. This is a controller that has the interfaces needed to link with the Hall sensors of the DB59 brushless motor.

The downside of this "kit" is that it is not plug and play.

Although the Industrial Sewing machine motor "kit" is more powerful than a watchmakers lathe would need it is plug and play. The Jack sewing machine motor kit was bought off eBay from sewit4you at £99.

PM me for more info.

Clive

Dell

To power the Pultra I would recommend one of the Industrial sewing machine motor kits being offered on "the Bay" and especially the one made by Jack. The kit has a powerful ( 3/4 HP) brushless DC motor, with mounting components and includes the motor electronic drive unit similar in function to a VFD and all for circa £100. The kit is truly "plug and use" with no wiring up needed. The motor can be mounted in an under drive configuration, as it is usually fitted on a sewing machine, or behind the machine. Interestingly the Mardrive unit was originally designed and used on industrial sewing machines and I believe the stand the Pultra was offered on was also derived from the same.

I have my sewing machine motor mounted on a bracket just behind the headstock and have used a VB 8x375Li belt to couple it to the spindle pulley. There are pictures of my set up posted on the ME site. The motor can provide extremely high torque even at low speeds so a countershaft arrangement isn't really necessary. If an overhead drive arrangement for milling/gear cutting etc is needed then just buying a separate motor is probably easier and since the motor is so small , about 100mm cube, it could be mounted on the overhead drive column.

The only downside I have found so far is that speed control algorithm of the drive unit is designed for sewing machines and from the OFF position goes to a fixed low speed setting ( can be preset to between 100 and 200 rpm) before moving through to a linear speed control region that goes from the low speed setting to the max speed which can also be pre-set up to 4000 rpm. I've changed the motor pulley to a smaller one that matches the Pultra spindle pulley to limit the max spindle speed to 4000 rpm as the original motor pulley would have e driven it at 8000 rpm on max motor speed obtainable. I'm not sure what the max spindle speed is for a plain bearing Pultra but I'm sure the ball bearing head is rated to beyond 8k rpm.

Another feature of the motor drive unit is that it provides servo speed control so the motor can accelerate and decelerate to the set speed demand vey quickly and the speed doesn't vary much with load. Not much of an issue with a direct spindle drive coupling and collets but could be if using a high inertia countershaft system and a big chuck.

I've found that the Brushless DC are exceptional performers and have recently "upgraded" my Bergeon 30535 watchmakers lathe base and motor unit with a BLDC motor to replace the noisy, dusty and smelly brushed AC motor. The BLDC motor runs virtual silently and there is no smell of ozone or carbon dust generated by the arcing brushes as a plus. To do this I used a BLDC motor controller used for electric bikes and COTS 24V DC power supply module. All low voltage and safe to wire up and the EV bike controller is better in that it can control speed from zero to max speed in a single linear range.

I'm also thinking of doing the same to a Bergeon Multifix motor unit which is equally noisy and has very poor variable speed control which it does by moving the position of the brushes with respect to the stator.

There a some tiny 2kW ( 3HP ) BLDC motor available so I might try fitting one to my Colchester Chipmaster !!!

Clive