DC Motor Starting amps

[mjg204]

My question is, the amps on the nameplate of a DC motor,is that what it runs at? and do the amps spike on start up of that motor?Thanks in advance.

 

[Buhsman]

Hi, the amperage on the name plate is FLA(Full load amps), the amperage while running can very depending on the load. If the current exceeds the FLA, then you could possibly have the wrong size motor, or you have a mechanical falure somewhere in the system.

Yes, on start up the current will "spike up", this is called inrush current and it will be higher than the name plate FLA.

Best Regards
Buhsman

 

[jbartos]

Suggestion: The DC motor starting amps depend on the motor starting arrangement. The motor starting inrush current may be substantially reduced by soft starting devices.
The motor nameplate or full load rated current is not supposed to be exceeded to protect the motor against damages and premature aging.

 

[etom]

the nameplate amps is the full load rated, and is also accompanied by a service factor.
The load and the applied voltage( and accel/ decell time of a drives ramp will determine the "spike amps"
The current will become larger the faster you wish to accel the motor, ...or the heavier you load it. Most Dc motors can take 200% Ia for about 60 sec, but it will depend on the commutation ability of the motor, and brush loading. As long as there is no sparking , you are " black" and within the overload rating of the motor.
THIS DOES NOT INCLUDE THE THERMAL LIMITS...and you must not do it for very long.
It is not uncommon for rolling mil and crane motors to have curent limit and the Timed overloads set upwards of 200%-250% rated amps.It all depends on the motor, application , drive rating, and cooling.