[Cassandra]

WWhy can a speed control not be used on a soft start router? I have a table mounted Craftsman single speed (25000 no-load) soft start router that I would like to slow down for using my 1 3/4" bits. Can I do it?

Hi:

A soft-start module is a speed control that modifies the voltage waveform to the motor. Adding a speed control module in series with the soft-start would most likely destory the soft-start, or at least prevent the soft-start from working. The speed controller and the soft-start module both expect a sine wave (remember trig in school?) on their inputs. The output of either module is a sine wave with chunks notched out.

Cassandra

 

[Cassandra]

Hi Cassandra:

A soft start motor starts from the "off" to full RPM gradually? The alternative is the motor will try to achieve full rpm instantly. On a more powerful router, this could pull the router right out of your hands. Am I right in my assumption?

Are they also called "capacitive start" or is that another way of achieving the same thing?

I do have a "capacitive start" 1/3 hp motor on my "V-Drum" sander and it is not variable speed and it seems to be "soft start."

Note the fixed speed Hitachi M12CS(?) I think has soft start.

Hi Ron:

A soft-start is usually a controller connected to the motor. The controller ramps the torque produced by the motor from a low value at turn-on to full torque. The torque is controlled usually by limiting the current drawn by the motor.

A "capacitive start" motor uses a capacitor to provide additional torque until the motor reaches a high-percentage of rated speed. This is done to get the motor up to speed faster -- the opposite effect from a soft-start controller.

By using a capacitive start motor, the manufacturer can use a smaller rated motor (lower power or hp), relying on the capacitive start to compensate for the smaller starting torque of the smaller motor.

Cassandra