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Thursday, September 13, 2018

Magnetic Primary Resistant Starter

Magnetic Primary Resistant Starter is another method of reducing the starting current of a motor. It is applied to motors with moderate starting current.


Control Operation


Figures 10 (a) and (b) illustrate the power and control circuit respectively of a “Magnetic Primary Resistance Starter”.


Pressing the start push button will energize S contactor, TR timer. Contacts S (13-14) will close to maintain contact circuit. Contact S (1-2,3-4,5-6) will close and complete the circuit in figure 10 (a) from the three supply lines (L1,L2, and L3) down to contact S (1-2,3-4,5-6), O.L. (1-2,3-4,5-6), the 3 resistors R, and finally to the motor M. Motor M will start and reduce voltage since in it is in series 3 resistors R. See simplified illustration in figure 10 (d).

Magnetic Primary Resistant Starter
Illustrates the power circuit of the “Magnetic Primary Starter”.


After a few second, the .delay contacts TR (8-6) will closed to energize contactor R coil (A-B). This will close contact R (1-2,3-4.5-6), see figure 10 (a). With contacts R (1-2,3-4,5-6) closed, the 3 resistors R are by pass and the motor M is now connected directly to the 3 lines L1,L2, and L3. See simplified illustration in figure 10 (d).

Magnetic Primary Resistant Starter
Illustrates the control  circuit of the “Magnetic Primary Starter”.


Pressing the stop push button will de-energize contactor S and timer TR. Contacts S (13-14) and S (1-2,3-4,5-6)will open. The 3-phrase motor M will stop. Contacts TR (8-6) will open to de-energized contactor R. Contact R (1-2,3-4,5-6) will open to de-energized the contactor R. the circuit condition will bring to the one shown in figures 10 (a) and (b).

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Magnetic Primary Resistant StarterMagnetic Primary Resistant Starter


(a) Illustrates the power circuit of the “Magnetic Primary Starter”.
(b) Illustrates the control  circuit of the “Magnetic Primary Starter”.
(c) Motor in series with the 3 resistors at the starting.
(d) Motor directly connected to the supply line when it is already in the stable condition.

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