Spindle moulder

[cutting42]

It makes me think that to old saw about a 3-phase "horse" being bigger than a single-phase "horse" might have some truth to it - at least in terms of starting torque.
Scrit

Hi Scrit

Single phase induction motors can definately have a lower starting torque. There is a type of single phase called "shaded pole" where part of each pole field there is a copper shield which helps provide the moving field to drive the motor round. This has little effect on the final speed and ultimate power but does result in low starting torque. 3 phase does not need to be shaded hence has 100% torque at 0 revs.

 

[ProShop]

John

Thanks for taking the time to add to the debate. I find your comments about steel vs. alloy tenoning discs particularly interesting, especially in light of having been on 3-phase myself for very many years now. It makes me think that to old saw about a 3-phase "horse" being bigger than a single-phase "horse" might have some truth to it - at least in terms of starting torque.
Scrit

I went today to see a fellow woodworker who is all 3 phase machinery and took some of my blocks to try, and yes there is a big difference between a single phase horse power and a 3 phase horse power. The 3 phase spun up so easily. I always thought there might be some difference but............:shock:.

So all my future bets on the national will be on 3 horses & not on a single horse

 

[RogerS]

I had to hold the start in longer than I would really wish to.

John..can you please expand a little on what you mean? Is there an interlock on the SM that is speed dependent?

Thanks

 

[ProShop]

Roger,

It's just the difference between induction motors & brush motors.
I'm not an expert here, but in my simple laymans terms, induction motors have a low start up torque compared to brush motors, so when you press the start button on my machine you engaging a capacitor to assist the motor to spin up when it has a load on, when it reaches a certain speed another capacitor kicks in and then it gets to full speed. Were only talking a couple of seconds or so here. If I use a small alloy block you just press start like starting say a drill for instance, it's instant.

So when I have a heavy block in the moulder you have to hold the start button in until it reaches full speed, when I tried a really big block I was holding the start button in for a few seconds and you could see & hear the motor really struggling to get up tp speed and a couple of times it would simply trip out. so on my 4 hp machine there is a limited to the size of block I can realistically use, I say size. but it's a weight/mass issue really.

 

[RogerS]

Thanks, John. Does this tie in with the contactor block (NVR on/off switch) on the start/stop panel holding in? I did have a sense that it only energised and locked in once the motor was up to speed but my enquiries along this line were poo-poo'd. Your comments suggest that my intuition was perhaps right...??

 

[Freetochat]

Thanks, John. Does this tie in with the contactor block (NVR on/off switch) on the start/stop panel holding in? I did have a sense that it only energised and locked in once the motor was up to speed but my enquiries along this line were poo-poo'd. Your comments suggest that my intuition was perhaps right...??

This is a feature of most Felder/Hammer single phase machines. I have it on all my machines. It was explained as assisting on power surge on startup (4 hp motors). After hitting the stop button, a few seconds later you can hear the capacitors clicking over. Usually it takes about 4 or 5 seconds on my machines. Just need to wait for the click before doing a restart.