I have dealt with many three phase and single phase dynamic braking
circuits, mostly in the 1-5 hp range and the number of phases on the motor
makes no difference, for braking ability.
The three phase braking circuits are more costly due to more contacts needed
to switch the load to the brake circuits. A simple SPDT switch will do for a
single phase saw.
The units I dealt with in 2000 ampere tapchangers typically used DC
injection (some were friction and some regenerative) and were set to time
out and allow the mechanism to coast onto a "top dead centre" position ready
for the next cycle. This could be made to stop "on the spot" if adjusted
this way but gave drift back to the brake initiating cam problems, at times
so the coast in was necessary. This would not be desirable to stop a machine
for a human usage.
Nah, there's nothing special about a three-phase motor that allows dynamic
That is what got me about 10 years ago and it wasn't a PM66. If was
an old Craftsman contractor's saw that I used to own. Shut the switch
of and started to walk away with a handful of small spaces I had just
cut off. I looked over my shoulder and noticed one on the table next
to be blade. In a brain-dead moment I over-reached the blade and got
nicked, to the bone, on a fingertip. Even the clunky old Craftsman
was still spinning down.
Stupid but it sure taught a lesson.
WOW! That is an exceptionally long time. I wonder if it is because of the
type belt that is used, not the typical v-belt rather the less resistant
That may be more to do with lighting. I recall 40 years ago my shop teacher
warning to be careful around the blade during spin down as it went and out
of phase with the floresent lighting. Basically working like an automotive
timing light. It did indeed appear to be paused a few times when shud town.
As it would slow to near in phase timing the blade would appear to go
backwards, stop, spin forward, etc. If the blade takes an exceptionally
long time to come to a stop the "in phase" periods with the lighting would
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.