[Unknown]

How much speed can be increased of a dc motor with the help of field control method?
How much speed can be increased of a dc motor with the help of field control method?

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[Hamid]

In addition of mechanical limitation , there are some electrical limitation for speed variaion in dc motor as following items: Field Resistance Control The lower the field current in a shunt (or separately excited) dc motor, the faster it turns: and the higher the field current, the slower it turns. Since an increase in field current causes decrease in speed, there is always a minimum achievable speed by field circuit control. This minimum speed occurs when the motor

[Jean]

Dear Hamid, Thank you and congratulations for your blog and your expertise ! I would like to say that the speed increase of a DC motor through field working weakening is also limited by the armature reaction flux that becomes very significant versus the inductor decreased flux , distorting it and leading to speed and current instability at high velocity (even on compensated machines). I faced this phenomenon on hoisting machines working at constant power between 2.5~3.5 times their base speed .

[Hamid]

Dear Jean, Thank you very much for your good comment. Best Regards Hamid

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