We know on undervoltage an ac motor will tend to draw overcurrent. But this should be due to the frequency factor, with frequency acting as a set point for the speed. But is this applicable to dc motor, which doesnt have such set point, and hence in a dc motor current should be proportional to voltage right?
At decrease voltage than designed for, motor will draw much less present day. and characteristic much less torque, much less rpm, and much less skill output .regardless of the incontrovertible fact that maximum DC vehicles use the rotation to tension a cooling fan, overheating should not be a difficulty see you later as motor is popping. Motor ought to run for a jiffy, on greater voltage see you later because of fact the insulation, and brushes can stay to inform the story the voltage. best subject is that of heat dissipation. greater voltage ability greater present day, and so greater warmth. Motor has a thermal mass and it will take fairly time for factors to warmth up and insulation to start to soften (there is likewise thermal resistance between factors, meaning one area could get too warm in the past yet another has even began to warmth up). must be available to apply a chopper tension to coach the motor on/off quickly. the job cycle (share of time motor is on for) regulates the common skill, and that still will alter the heating. collectively as the motor is way less effective while fed with the aid of a chopper (greater heating than on authentic DC ), chopper drives are in many instances used for speed administration, and if this is already there, it may desire to be trivial to enforce an common heating limiter AFIK batteries are consistently DC output. won't be in a position to work out how a battery could desire to be made to at as quickly as output AC (ie without DC to AC converter), yet one among these theoretical battery could desire to be fairly smart/thrilling
In a DC motor, speed is proportional to voltage and current is proportional to load torque. If the voltage is reduced, the speed will tend to drop. With most loads, the torque required will be the same or less at lower speeds. That would mean the current could stay the same or go down. There are loads that require higher torque at reduced speeds, but I believe that such loads require a motor control system that would regulate the current or otherwise determine the effect of insufficient available voltage. PS1 If the voltage applied voltage to a DC motor is reduced, the motor does not lose the capability to produce torque. It will operate at a lower speed, and the current might increase somewhat, but it won't stall and draw high current like an AC motor would. However, if the load increases and causes the motor to stall, the motor will draw high current unless the power supply limits the current by reducing the voltage.
DC or AC doesn't matter. All motors draw high current on starting and it drops as they generate counter EMF. Big motors may have to be started incrementally. Small motors can handle the load but only for seconds. Low voltage is a problem either way. If a motor can't start and run, it can't generate counter EMF and becomes a pure resistance load. Since most motors have low resistance when stalled, they tend to burn. They all do that, AC or DC. If you can't get the motor turning fast enough, it'll burn. It isn't about frequency factor as much as about getting the motor to run fast enough to generate counter EMF. This is a problem at campgrounds where people burn out air conditioning units in their trailers because the voltage is too low after coming through the campground lines. It would be the same if it was DC.
