How a DC Magnetic Motor Controller Works – Basic Troubleshooting of an older DC Motor Starter

As industrial facilities and manufacturing developed over the years, and so have the techniques we drive the machinery. By power, I am referring to the controlling or perhaps initiating movement to perform a meditation process. The key element here is the industrial motors themselves. Whether they are small, medium, or large, motors need being managed. They have for being started, stopped, and varied in overall speed for safety and also to properly perform their selected function. A motor rotating at unsafe speeds can be risky to personnel and dangerous to the machines to which they are connected. The motor controller is necessary to do just that. Influence of the startup and also the velocity to an appropriate speed, then the monitoring of the engine to make sure it’s operating within its power rating, and needless to say the stoppage of the engine.


For decades, a magnetic dc motor control was the best way to acquire the task finished. These sometimes complicated circuits composed of relays, contactors, timers, plus resistors are likely to be found anyplace there was an industrial electric motor. At the time, they had been technology which is brand new replacing drum controllers which often utilized the human element to manage a motor’s acceleration. on these controllers, an operator had the responsibility of switching on the motor along with bringing it up to its right speed utilising a handle connected to a drum of contacts. The more quickly the operator turned the deal with, the faster the motor accelerated. Operating speed for the motor may also be controlled making use of the handle by stopping at a certain position short of total deflection. Motors could be reversed making use of these controls by rotating the handle in the complete opposite course. Drum controllers relied too much on an operator’s tender touch to become safe and efficient. The dc magnetic controller very easily evolved into the established technique of motor control in its time.

The controlled acceleration of a dc motor along with its controlled top speed designed these controllers well suited for industrial machinery. The names Cutler Hammer, Allen Bradley, Westinghouse, and General Electric were synonamous with motor control. They all was comprised of similar circuitry but various manufacturers had their own improvements & idiocyncrasies. The motor is generally started and also stopped from a commonly open and typically closed push button assembly. This manages a relay commonly labeled CR, for control relay. The control circuit had also been interfaced with overload as well as overtemp contacts for shelter of the motor, the machinery, and man personnel. A primary contactor is indicated by an m contactor. motor control circuit diagram forward reverse pdf are intended with big present carrying contacts since they’re accountable for placing and disconnecting the primary circuit of the armature. As soon as the control circuit is energized, the accelerating of the engine is initiated using a series of resistors along with contactors. These contactors are labeled 1A, 2A, 3A, so forth. Accelerating contacts are opened and closed in accordance with the armature current draw in a number of controllers and by timers in others.

Another contactor referred to as FA contactor, or maybe area accelerating contactor, remained closed during the acceleration of the engine. This contact assures that detailed power is used to the shunt arena around the engine until it is operating for a continuous rate. It imay be also called the FF contactor, or maybe complete field contactor by certain makers. As soon as the electric motor has achieved its correct speed, the FF or FA contactor would open and speed control of the engine would be handed over to some rheostat. The rheostat might possibly be in set with the shunt field. By varying the current flow through the shunt field, motors might be controlled for speed. A few forms of shelter in these motor starters happen to be added in case of electric motor winding failure or too much mechanical loading. The FL contactor, or area loss contactor was typically created with line coil in sequence with the shunt field. An open in the shunt field circuit would bring about the subject loss contactor to start and turn off the control circuit acting much like pressing a stop button. The other form of protection would be as well as overload circuit. The OL contactor or even the OLX contactor ended up being used to monitor an overload condition. These contactors in addition would act as much like pressing a stop button. an overload generally senses too much current flow through the armature of the motor caused by inner motor winding shorts and opens, motor brush failure, a physical problem as a result of used motor bearings, or perhaps a technical failure in the device to that the electric motor is coupled.

Various other optional items added to these magnetic motor starters were components like external current meters for personnel to observe. A load meter is a good illustration of present day monitoring improved to show the load on the electric motor in time which is real on to the operator. There was also reversing options which made it possible for the course of the motor to be improved with a switch or perhaps by turning a mechanical handle. With a familiarity of magnetic dc motor starters along with fundamental electrical skills, troubleshooting the control circuits of any of these manufacturers becomes easier with experience because basic schematics and the idea from Cutler Hammer, Allen Bradley, GE, and Westinghouse were constantly similar.

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