Here is a list of all the postings Michael Briggs has made in our forums. Click on a thread name to jump to the thread.
|Thread: Why mostly manual cars in UK|
Re auto drivers with their foot on the brake in a queue. I have had automatics from Audi, Bmw and now VW, all with electronic handbrakes. The brake lights come on when the car applies the handbrake and you can't turn them off.
|Thread: Suggestions to pack round DC motor so bracket holds|
+1 Emgee, I like simple effective solutions.
|Thread: Inverters and stop switches|
Hello Dave, by "the exceptions" I meant that there are VFDs that are capable of having the load switched while the drive is running, large and small.
The point I would like to make clear to the forum is that the type of VFDs we generally have in our workshops when at rest and powered are unlikely to start due to failure of internal control circuit but are not safe. I recommend that when you are setting up a job on the faceplate for example, you isolate the power. I don't isolate for everything, that is my choice.
SOD with due respect, I haven't spotted that VFD's are not all equal, I have worked with them for the last 40 years.
I am pleased it makes some sense to you, I will do my best to respond to any questions you have to anything that doesn't make sense.
I can Robert :
Bread dough mixer with a 90 Kw motor. The risk assessment required a category 4 safety system, a VFD powered up and stopped is not safe enough to meet HSE requirements. You can of course isolate the supply making the system safe but the VFD was not rated for the required 10 power cycles per hour. The solution was disconnection of the motor from the VFD. The machine was guarded (mandatory) but locked until the VFD brought the motor to a standstill and then was isolated from the VFD so the VFD could remain powered up and the system made safe.
Reverse operation on startup, lock access gates engage VFD connection to drive then start the VFD.
Outcries from the forum "what has that got to do with my machines", perhaps not a lot, a VFD at rest and powered up is unlikely to start by its own accord but it is possible. So when I am setting up on the faceplate for example I isolate the lathe.
For some time there have been VFDs available with a safe off facility that can make the VFD safe while powered up but no need for that in my workshop.
Hope that makes sense,
Edited By Michael Briggs on 08/11/2019 21:31:37
A switch between a VFD and the motor does not risk damaging the drive provided that it is only opened or closed when the drive is at standstill though there are exceptions. In industrial installations is not uncommon for a drive to be ramped down to standstill and then disconnected from the VFD output.
An "emergency stop button" wired in series with the regular stop button is just another stop button. I normally stop my machines with the stop button and the VFD ramps down to standstill. I have emergency stops on my machines, they isolate power from the VFD. Fortunately I have not had to use them, but if I do I know the machine will stop even if the VFD control has failed.
|Thread: 'Bristol Handles'|
If you can source a female lever with the required handle length, is is a simple task to make a shaft to convert from a larger thread to M4 and loctite it place. Michael
|Thread: portable LED floodlight , power source ?|
If possible I would put it back together with the original electronics and measure the operating voltage. Alternatively connect a variable voltage power supply and increase the voltage to an acceptable level of brightness, taking care not to cook it. Michael
|Thread: MIDLANDS MODEL ENGINEERING EXHIBITION|
At the Harrogate shows the arc stand was always busy. When they initially reduced their presence it was a machine only stand so it is unlikely that the cost of transporting machines was an issue.
|Thread: VFD Instructions|
With the motor parameters correctly set you should get full motor protection.
|Thread: VFD and screwcutting|
I have had a look at the literature for Rockwell drives, the acceleration and deceleration times are defined as the time it takes to accelerate from rest to maximum speed or decelerate from maximum speed to rest, makes sense to me. Other manufacturers may have different ideas.
I did my own VFD setup which is similar to the Newton Tesla setup except that I have a separate jog button and an emergency stop that isolates the drive. I use the jog button for screw cutting and tapping, works well for me, the drive stops as soon as you release the button.
If a stop limit switch is triggered by the carriage then it will probably have to either be taken out of circuit or mechanically de-activated to allow you to reverse the drive back to the start of the thread.
|Thread: 3 Phase|
Sorry, hadn't looked at Bill's link, Michael
Davey, my Fobco drill has a similar motor, I would have to take the motor off to see the motor plate. The lid of the terminal box shows how to connect for high and low voltages. It is probably the same as your motor :
|Thread: Why does the micrometer have a second knurled segment|
Photo finish Paul, let’s call it a draw
That’s a new one to me Alan, I thought the second knurled grip was to provide additional functionality as a G clamp.
|Thread: Locking Levers|
I sourced metal handles for my grinding rest from WDS as referenced by George. Excellent quality and they didn't break the bank.
|Thread: good service Arc eurotrade|
I rate Arceurotrade as a reasonably good supplier, I have had problems on two occasions. The first was with a ball bearing collet nut that felt like it was full of sand, it was replaced promptly.
The second instance was when I purchased two pairs of Stevenson’s 10 20 40 blocks. One of the blocks was manufactured with a hole considerably out of alignment. When I spoke to them about the problem I was told that they would not replace such a low cost item (£16) but I could return it for a refund which I did. I did not receive a refund for the return postage on either occasion.
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