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Jun 15, 2017 4:51 pm
Jun 15, 2017 4:51 pm
Subject: Re: LG 45 wiper motor amperage/wattage
Hi Bill,
A motor draws a much higher current at start up ( "inrush current" ) this only last momentarily and dies away to the normal running current as the motor reaches running speed, to be honest I am not sure what would happen to a DC brush motor with this PWM device...I found some info on the web, take a look at this link:
http://www.electronics-tutorials.ws/blog/pulse-width-modulation.html
As I understand it, with a DC motor the PWM effectively reduces the effective voltage at the terminals and hence the motor runs slower. Power = voltage X current so with less voltage the current will increase unless the load on the motor is proportionally reduced.
I see your argument about running slower for half the time, then motor should do less work at a lower velocity and also power =
work / time but I suggest the actual load on the motor is largely from the friction resistance from driving the cable mechanism and that part of the load is not directly related to velocity especially when cold, due to the grease lubrication for the cable and gears hence the load will not be proportional to the speed.
I believe the current may well increase.
Coming back to running too fast, on reflection this seems odd. Have you checked the voltage at the terminals as the wiper motor may be getting more than 12 volts, perhaps the voltage regulator on your car is not working correctly?
Hope the above helps
Bill
Hi Bill,
A motor draws a much higher current at start up ( "inrush current" ) this only last momentarily and dies away to the normal running current as the motor reaches running speed, to be honest I am not sure what would happen to a DC brush motor with this PWM device...I found some info on the web, take a look at this link:
http://www.electronics-tutorials.ws/blog/pulse-width-modulation.html
As I understand it, with a DC motor the PWM effectively reduces the effective voltage at the terminals and hence the motor runs slower. Power = voltage X current so with less voltage the current will increase unless the load on the motor is proportionally reduced.
I see your argument about running slower for half the time, then motor should do less work at a lower velocity and also power =
work / time but I suggest the actual load on the motor is largely from the friction resistance from driving the cable mechanism and that part of the load is not directly related to velocity especially when cold, due to the grease lubrication for the cable and gears hence the load will not be proportional to the speed.
I believe the current may well increase.
Coming back to running too fast, on reflection this seems odd. Have you checked the voltage at the terminals as the wiper motor may be getting more than 12 volts, perhaps the voltage regulator on your car is not working correctly?
Hope the above helps
Bill