Re: [CAD_CAM_EDM_DRO] Re: LARGE DC MOTOR speed control question

The capacitors of a straight rectified power supply will see 1.4 times the
input AC voltage, minus the voltage drop across the rectifiers. When the
voltage is loaded down an 120 volt input will result in a voltage that is
close enough to the 90 volt DC rating of a DC motor, and will operate OK,
also the 220 volt AC will operate the 180 volt motors. This is in the real
world usage's.
Most variable speed motor controllers for DC, use a SCR for the controlling
and switching/rectifying element, and the controls can be set for a maximum
speed, and this directly relates to maximum voltage the motor sees. Because
most variable supplies for smaller motors the DC voltage is half wave
rectified, and sags greatly under load. This is what makes the above
statements usable.
bill