28-01-2018, 04:14 PM
(28-01-2018, 02:33 PM)boater sam Wrote: He glued the diodes on.
What is not mentioned is the polarity of the diodes, are they in series or parallel?
Must try this sometime.
There is a note that the current was seen to reduce with an applied load, this is normal with series wound universal motors up to a point and with squirrel cage motors. We had fan units that needed a restriction in the ducting to reduce the running current, perverse but true.
Not really perverse Sam, the load for a fan is the air it has to move, restrict the air flowing into the fan and you reduce the load and therefore the current.
People often misinterpret the increased revs on a vacuum cleaner motor when the pipe becomes blocked as a sign of increased load, however it is the decreased load that in fact is causing the motor to over speed, this could easily be proven by a check on the current being drawn actually dropping, just as would be the case with a synchronous motor in your example.
The reason that a vacuum cleaner motor is likely to be destroyed quite quickly when abused like this is because not only will the revs cause unsafe levels of centrifugal force, but also the normal vac motor relies upon the gale of cooling air to allow it to produce its insane power levels.
Andy.
