{"id":8444,"date":"2021-08-05T12:00:57","date_gmt":"2021-08-05T20:00:57","guid":{"rendered":"https:\/\/www.linquip.com\/blog\/?p=8444"},"modified":"2025-08-28T02:32:11","modified_gmt":"2025-08-28T10:32:11","slug":"separately-excited-dc-motor","status":"publish","type":"post","link":"https:\/\/www.linquip.com\/blog\/separately-excited-dc-motor\/","title":{"rendered":"Separately Excited DC Motor"},"content":{"rendered":"<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_82_2 counter-hierarchy ez-toc-counter ez-toc-grey ez-toc-container-direction\">\n<div class=\"ez-toc-title-container\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">Table of Contents<\/p>\n<span class=\"ez-toc-title-toggle\"><a href=\"#\" class=\"ez-toc-pull-right ez-toc-btn ez-toc-btn-xs ez-toc-btn-default ez-toc-toggle\" aria-label=\"Toggle Table of Content\"><span class=\"ez-toc-js-icon-con\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">Toggle<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #999;color:#999\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewBox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #999;color:#999\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewBox=\"0 0 24 24\" version=\"1.2\" baseProfile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/span><\/a><\/span><\/div>\n<nav><ul class='ez-toc-list ez-toc-list-level-1 ' ><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/www.linquip.com\/blog\/separately-excited-dc-motor\/#What_is_a_Separately_Excited_DC_Motor\" >What is a Separately Excited DC Motor?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/www.linquip.com\/blog\/separately-excited-dc-motor\/#Equations_of_Voltage_Current_and_Power_for_a_Separately_Excited_DC_Motor\" >Equations of Voltage, Current, and Power for a Separately Excited DC Motor<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/www.linquip.com\/blog\/separately-excited-dc-motor\/#Operating_Characteristics_of_a_Separately_Excited_DC_Motor\" >Operating Characteristics of a Separately Excited DC Motor<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/www.linquip.com\/blog\/separately-excited-dc-motor\/#Speed_Control_of_a_Separately_Excited_DC_Motor\" >Speed Control of a Separately Excited DC Motor<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/www.linquip.com\/blog\/separately-excited-dc-motor\/#Speed-Torque_Characteristic_of_a_Separately_Excited_DC_Motor\" >Speed-Torque Characteristic of a Separately Excited DC Motor<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"https:\/\/www.linquip.com\/blog\/separately-excited-dc-motor\/#Applications_of_Separately_Excited_DC_Motor\" >Applications of Separately Excited DC Motor<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-7\" href=\"https:\/\/www.linquip.com\/blog\/separately-excited-dc-motor\/#Download_separately_excited_dc_motor_PDF\" >Download separately excited dc motor PDF<\/a><\/li><\/ul><\/nav><\/div>\n<p>What is a Separately Excited DC Motor? Like other motors, these devices also have both rotors and stators. Stator refers to the static section of the device, which contains the field windings. The rotor is the rotating armature which consists of armature coils or windings. A separately excited DC motor includes some field coils similar to that of shunt-wound type. The name shows the structure of this type of motor. Typically, in other DC motors, the armature coil and the field coil are both powered from a single source. The field of them does not require any separate excitation. However, in a separately excited DC motor, a separate supply is used to excitation both the armature coil and the field coil.<\/p>\n<p>These motors, like other DC motors, feature both a stator and a rotor. The field windings make up the stator, which is the static element of the motor. The rotor, on the other hand, is the moving armature, which is made up of armature windings or coils. The field coils of a separately stimulated dc motor are comparable to those of a shunt wound dc motor. The name alludes to how this sort of engine is built.<\/p>\n<p>Separately excited DC motors are available from a variety of <a href=\"https:\/\/www.linquip.com\/suppliers-companies?category_id=31&amp;cn=dc-motors\"><strong>Suppliers and Companies<\/strong><\/a>, as well as various manufacturers and distributors, and there are several \u00a0<a href=\"https:\/\/www.linquip.com\/industrial-directories\/31\/dc-motors\/for-sale\"><strong>Separately Excited DC Motors for Sale<\/strong><\/a> on Linquip. There is a complete list of Separately excited DC motor services on the Linquip platform that covers all OEM fleets. Please call \u00a0<a href=\"https:\/\/www.linquip.com\/experts?category_id=31&amp;cn=dc-motors\"><strong>Separately Excited DC Motor Experts<\/strong><\/a> in Linquip to learn more about how to connect with a diverse group of <a href=\"https:\/\/www.linquip.com\/suppliers-companies\/service-provider?category_id=31&amp;cn=dc-motors\"><strong>Service Providers<\/strong><\/a> who consistently deliver high-quality products.<\/p>\n<p style=\"text-align: center;\"><span style=\"text-decoration: underline;\"><a href=\"https:\/\/www.linquip.com\/industrial-directories\/31\/dc-motors\/for-sale?utm_source=blog&amp;utm_medium=content&amp;utm_campaign=CRO&amp;utm_term=&amp;utm_content=for_sale\" target=\"_blank\" rel=\"noopener\"><span style=\"font-size: 14pt;\"><strong>\u21d2 View a List of DC Motors for Sale and Their Suppliers \u21d0<\/strong><\/span><\/a><\/span><\/p>\n<h2><span class=\"ez-toc-section\" id=\"What_is_a_Separately_Excited_DC_Motor\"><\/span><strong>What is a Separately Excited DC Motor?<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>As the name presents, in the case of a separately excited DC motor, the main supply is given separately to the armature and field windings. The major distinguishing fact in these forms of DC motor is that the armature current does not move across the field windings as the field winding is powered from a separate external supply of DC. From the torque equation of motors, we know that:<\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: center;\"><span class=\"katex-eq\" data-katex-display=\"false\"> T_{g} = {K}_{a} \\phi {I}_{a} <\/span>\n<p>&nbsp;<\/p>\n<p>So, the torque, in this case, can be changed by modifying the field flux (\u03c6), independent of the current of the armature (I<sub>a<\/sub>). The figure below presents the separately excited DC motor.<\/p>\n<figure id=\"attachment_8445\" aria-describedby=\"caption-attachment-8445\" style=\"width: 408px\" class=\"wp-caption aligncenter\"><img decoding=\"async\" class=\"size-full wp-image-8445\" src=\"https:\/\/www.linquip.com\/blog\/wp-content\/uploads\/2021\/05\/1-separately-excited-dc-motor_Reference-electrical4u.com_.gif\" alt=\"Separately Excited DC Motor\" width=\"408\" height=\"272\" title=\"\"><figcaption id=\"caption-attachment-8445\" class=\"wp-caption-text\">What is a Separately Excited DC Motor (Reference: <strong>electrical4u.com<\/strong>)<\/figcaption><\/figure>\n<p>Here, the field coil is powered from a separate DC voltage supply, and the armature coil is also powered from another source. Armature voltage supply may be variable but, an independent fixed DC voltage is applied to induce the field coil. Therefore, those coils are electrically separated from each other, and this junction is the main feature of this type of motors.<\/p>\n<h3><strong>Definition of a Separately Excited DC Motor<\/strong><\/h3>\n<p>Direct current motors have been using to provide the field of adjustable speed controllers for over a century; they are still the most applicable option if a controlled electrical drive working over a wide velocity level is specified.<\/p>\n<figure id=\"attachment_18553\" aria-describedby=\"caption-attachment-18553\" style=\"width: 548px\" class=\"wp-caption aligncenter\"><img decoding=\"async\" class=\"size-full wp-image-18553\" src=\"https:\/\/www.linquip.com\/blog\/wp-content\/uploads\/2021\/08\/10-Separately-Excited-DC-Motor-Reference-alibaba.com_.jpg\" alt=\"\" width=\"548\" height=\"380\" title=\"\" srcset=\"https:\/\/www.linquip.com\/blog\/wp-content\/uploads\/2021\/08\/10-Separately-Excited-DC-Motor-Reference-alibaba.com_.jpg 548w, https:\/\/www.linquip.com\/blog\/wp-content\/uploads\/2021\/08\/10-Separately-Excited-DC-Motor-Reference-alibaba.com_-300x208.jpg 300w\" sizes=\"(max-width: 548px) 100vw, 548px\" \/><figcaption id=\"caption-attachment-18553\" class=\"wp-caption-text\">Separately Excited DC Motor Reference <strong>alibaba.com<\/strong><\/figcaption><\/figure>\n<p>This is because of their excellent performance features and control properties; the only essential drawback is the mechanical commutator which reduces the speed and power of the motor, maximizes the inertia and the axial length, and needs too periodic maintenance than the other types. The commutator is removed with alternating current motors, supplied by variable frequency static power converters, but the cost can be increased because of their complexity.<\/p>\n<p>This is one of the main reasons why new AC controllers could not quickly supplant DC types, once the semiconductor technology had significantly improved.<\/p>\n<p>The principle of a DC motor performing in steady-state is assumed to be known, but let us discuss some basic facts below.<\/p>\n<h3><strong>Working Principle of a Separately Excited DC Motor<\/strong><\/h3>\n<p>A schematic cross-section across a two-pole DC motor is presented in the next figure, including the fixed stator S and the cylindrical rotor, introduced as armature A. Once rotor and pole shoes are always connected in order to decrease the iron wastes caused by the varying magnetic flux, the rest of the stator is laminated just in huge machines, when the device is needed to perform with fast varying torque and speed or once a static power converter with greatly distorted currents and voltages is used as the power supply.<\/p>\n<p>The basic poles (M and P) are connected with the field windings, moving the field current i<sub>e<\/sub> which runs the main flux across the rotor and stator. A closed armature coil is set in the axial slots of the rotor and combined with the commutator bars; it is provided by the brushes and the commutator produces the armature current i<sub>a<\/sub>. This generates a distributed ampere-turn (mmf) wave, fixed in the space and rotated in the direction of the quadrature axis, orthogonal to the basic axis, so that maximum output torque for the armature current can be created.<\/p>\n<p>In the case of the great distance in the quadrature direction, the resulting armature flux is much smaller than the basic flux. It can be decreased even further by setting compensating coils in the axial slots on the pole shoes and arranging them in series with the armature. Their opposing ampere-turn stops the quadrature field induced by the armature and eliminates the undesired armature reaction, which otherwise wants to distort the even distribution of the main flux under the poles across the circumference of the rotor.<\/p>\n<figure id=\"attachment_8446\" aria-describedby=\"caption-attachment-8446\" style=\"width: 784px\" class=\"wp-caption aligncenter\"><img decoding=\"async\" class=\"size-full wp-image-8446\" src=\"https:\/\/www.linquip.com\/blog\/wp-content\/uploads\/2021\/05\/2-Cross-section-a-and-schematic-circuit-b-of-a-DC-machine.jpg\" alt=\"Separately Excited DC Motor\" width=\"784\" height=\"532\" title=\"\" srcset=\"https:\/\/www.linquip.com\/blog\/wp-content\/uploads\/2021\/05\/2-Cross-section-a-and-schematic-circuit-b-of-a-DC-machine.jpg 784w, https:\/\/www.linquip.com\/blog\/wp-content\/uploads\/2021\/05\/2-Cross-section-a-and-schematic-circuit-b-of-a-DC-machine-300x204.jpg 300w, https:\/\/www.linquip.com\/blog\/wp-content\/uploads\/2021\/05\/2-Cross-section-a-and-schematic-circuit-b-of-a-DC-machine-768x521.jpg 768w, https:\/\/www.linquip.com\/blog\/wp-content\/uploads\/2021\/05\/2-Cross-section-a-and-schematic-circuit-b-of-a-DC-machine-696x472.jpg 696w, https:\/\/www.linquip.com\/blog\/wp-content\/uploads\/2021\/05\/2-Cross-section-a-and-schematic-circuit-b-of-a-DC-machine-619x420.jpg 619w\" sizes=\"(max-width: 784px) 100vw, 784px\" \/><figcaption id=\"caption-attachment-8446\" class=\"wp-caption-text\">Cross-section and Schematic Circuit of a Separately Excited DC Motor (Reference: <strong>electrical-tutorials.com<\/strong>)<\/figcaption><\/figure>\n<p>Compensating coils are popular only on huge machines or converter-fed devices for heavy-duty cases such as steel-mill or traction drives. Compensated DC motors can tolerate higher overloads than uncompensated forms. The armature current may increase much quicker and greater current harmonics are acceptable without detrimental influences on the commutation, i.e. sparking of brushes. This is too important if the motor is supported by a static converter.<\/p>\n<p>The commutating poles (C and P), installed between the main poles and also carrying the armature current, have the main task of locally varying the field in the neutral place, in order to obtain rapid and spark-free commutation. This is performed by producing an appropriate voltage in the armature coil temporarily reduced by the brushes.<\/p>\n<p>The principle of commutation is very simple, where the closed armature section of a two-pole DC motor is generally performed, providing the brush positions at two consecutive instants of time. Generally, when the feeding points of the winding are switched by the relative movement of the brushes to the next commutator bars, the commutating winding is immediately short-circuited, whereas the current is inverted.<\/p>\n<p>Because each winding, being embedded in slots covered by iron, presents some inductance, the commutation is a constant process that takes a finite time; this restricts the speed at which the device can perform without excessively sparking brushes. Visit <a href=\"https:\/\/www.youtube.com\/watch?v=dJxTjJ3XBVE\" target=\"_blank\" rel=\"noopener\">here<\/a><\/p>\n<h3><strong>What Is the Advantage of Separately Excited Dc Motor?<\/strong><\/h3>\n<p>Compared to self-excited DC generators, separately excited DC generators have a number of benefits. It has a broad range of output voltage and can function in stable conditions with any field excitation. The primary downside of these generators is that having a separate excitation source is quite costly.<\/p>\n<figure id=\"attachment_18556\" aria-describedby=\"caption-attachment-18556\" style=\"width: 487px\" class=\"wp-caption aligncenter\"><img decoding=\"async\" class=\"size-full wp-image-18556\" src=\"https:\/\/www.linquip.com\/blog\/wp-content\/uploads\/2021\/08\/10-Separately-Excited-DC-Motor-advantages-Reference-alibaba.com_.jpg\" alt=\"\" width=\"487\" height=\"404\" title=\"\" srcset=\"https:\/\/www.linquip.com\/blog\/wp-content\/uploads\/2021\/08\/10-Separately-Excited-DC-Motor-advantages-Reference-alibaba.com_.jpg 487w, https:\/\/www.linquip.com\/blog\/wp-content\/uploads\/2021\/08\/10-Separately-Excited-DC-Motor-advantages-Reference-alibaba.com_-300x249.jpg 300w\" sizes=\"(max-width: 487px) 100vw, 487px\" \/><figcaption id=\"caption-attachment-18556\" class=\"wp-caption-text\">Separately Excited DC Motor advantages Reference <strong>alibaba.com<\/strong><\/figcaption><\/figure>\n<h2><span class=\"ez-toc-section\" id=\"Equations_of_Voltage_Current_and_Power_for_a_Separately_Excited_DC_Motor\"><\/span><strong>Equations of Voltage, Current, and Power for a Separately Excited DC Motor<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>In a separately excited DC motor, field and armature windings are excited to form two various DC supply voltages. In this motor, we have<\/p>\n<ul>\n<li>Armature current I<sub>a<\/sub> = Line current = I<sub>L<\/sub> = I<\/li>\n<li>Back emf developed:<\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n<p style=\"text-align: center;\"><span class=\"katex-eq\" data-katex-display=\"false\">E_{v} = V-I{R}_{a}<\/span>\n<p>&nbsp;<\/p>\n<p>where V is the main voltage and R<sub>a<\/sub> is the armature resistance.<\/p>\n<ul>\n<li>Power is drawn from the main source:<\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n<p style=\"text-align: center;\"><span class=\"katex-eq\" data-katex-display=\"false\">P=VI<\/span>\n<p>&nbsp;<\/p>\n<ul>\n<li>Mechanical power developed (Pm) = Power input to the armature \u2013 power wasted in the armature<\/li>\n<\/ul>\n<h2><span class=\"ez-toc-section\" id=\"Operating_Characteristics_of_a_Separately_Excited_DC_Motor\"><\/span><strong>Operating Characteristics of a Separately Excited DC Motor<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>Both in <a href=\"https:\/\/www.linquip.com\/blog\/shunt-dc-motors\/\">shunt-wound<\/a> and separately excited types, the field is supported from a regulated voltage, so that the field current is fixed. Thus, these two motors have identical speed-armature current and torque\u2013armature current features. In a separately excited DC motor, the flux is assumed to be constant.<\/p>\n<h3><strong>Speed \u2013 Armature Current (N \u2013 I<sub>a<\/sub>) Characteristics<\/strong><\/h3>\n<p>We know that the speed of a motor is related to the back EMF\/flux i.e. E<sub>b<\/sub> \/ \u03c6. Once the load is increased, back EMF and flux reduce because of the armature resistance reduction and armature reaction respectively. However, back EMF reduces more than flux, so that the speed of the motor slightly drops with the load.<\/p>\n<h3><strong>Torque \u2013 Armature Current (\u03a4 \u2013 Ia) Characteristics<\/strong><\/h3>\n<p>Here torque is related to the flux and armature current. Regardless of the armature reaction, flux is fixed and torque is related to the armature current I<sub>a<\/sub>. T\u2013 I<sub>a<\/sub> feature is a straight line passing across the origin. From the curve, we can understand that a large current is required to start heavy loads. So, this form of motor does not start on heavy loads.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Speed_Control_of_a_Separately_Excited_DC_Motor\"><\/span><strong>Speed Control of a Separately Excited DC Motor<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>The speed of this type of DC motor is determined by the following methods:<\/p>\n<ul>\n<li><strong>Field control:<\/strong> Reduction of the field increases the speed of the device while improving the field causes reduction in the speed. Speed regulation of this type of motor can be obtained by controlling the field. Field voltage control is applied by changing the voltage at the field circuit while keeping armature terminal voltage fixed.<\/li>\n<li><strong>Field rheostat control:<\/strong> Here a variable resistance is arranged in series form with the field coil. Therefore, the speed is determined by means of flux variation. Reluctance control is also used by variation of the reluctance of the magnetic circuit of the device.<\/li>\n<li><strong>Armature control methods:<\/strong> Speed regulation of a separately excited DC motor by armature control may be achieved by any one of the following methods: a) Armature resistance control (Here, the speed is determined by changing the source voltage to an armature. Typically, a variable resistance is used in the armature to change the armature resistance), b) Armature terminal voltage control that is used to change the voltage in the armature circuit.<\/li>\n<\/ul>\n<h2><span class=\"ez-toc-section\" id=\"Speed-Torque_Characteristic_of_a_Separately_Excited_DC_Motor\"><\/span><strong>Speed-Torque Characteristic of a Separately Excited DC Motor<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>The main formulation of a speed-torque Characteristic of a separately excited DC motor whose armature, including a total of Z con\u00adductors, is wound for 2P poles (the brushes separate the winding into 2 parallel paths), is<\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: center;\"><span class=\"katex-eq\" data-katex-display=\"false\">{V}_{a} = E+{I}_{a}{r}_{a}<\/span>\n<p>&nbsp;<\/p>\n<p>Where E is the back emf of the armature obtained by<\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: center;\"><span class=\"katex-eq\" data-katex-display=\"false\">E=\\frac{\\phi ZN}{60}\\frac{2P}{2a}={K}_{e}\\phi N={K}_{t}\\phi \\omega<\/span>\n<p>&nbsp;<\/p>\n<p>where \u03c9 is the angular speed introduced as<\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: center;\"><span class=\"katex-eq\" data-katex-display=\"false\"> \\omega=\\frac{2\\pi N}{60}<\/span>\n<p>&nbsp;<\/p>\n<p>and K<sub>e<\/sub> and K<sub>t<\/sub> are constants.<\/p>\n<figure id=\"attachment_8447\" aria-describedby=\"caption-attachment-8447\" style=\"width: 230px\" class=\"wp-caption aligncenter\"><img decoding=\"async\" class=\"size-full wp-image-8447\" src=\"https:\/\/www.linquip.com\/blog\/wp-content\/uploads\/2021\/05\/3-Separately-Excited-DC-Motor-structure.png\" alt=\"Separately Excited DC Motor\" width=\"230\" height=\"221\" title=\"\"><figcaption id=\"caption-attachment-8447\" class=\"wp-caption-text\">Separately Excited DC Motor Structure (Reference: <strong>electrical-tutorials.com<\/strong>)<\/figcaption><\/figure>\n<p>From the above equation, we get<\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: center;\"><span class=\"katex-eq\" data-katex-display=\"false\">N=\\frac{{V}_{a}-{I}_{a}{r}_{a}}{{K}_{e}\\phi }<\/span>\n<p>&nbsp;<\/p>\n<p>The torque produced by the device is given by<\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: center;\"><span class=\"katex-eq\" data-katex-display=\"false\">{T}_{d}=\\frac{1}{2\\pi }2P \\phi \\frac{{I}_{a}}{2a}Z={K}_{t}\\phi {I}_{a}<\/span>\n<p>&nbsp;<\/p>\n<p>Substituting for I<sub>a<\/sub> in the last formula, we have<\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: center;\"><span class=\"katex-eq\" data-katex-display=\"false\">N=\\frac{{V}_{a}}{{K}_{e}\\phi }-\\frac{{T}_{d}}{{K}_{t}{K}_{e}{\\phi }^{2}} {r}_{a}<\/span>\n<p>&nbsp;<\/p>\n<p>Once T<sub>d<\/sub> is zero, the corresponding speed N<sub>0<\/sub> is the no-load condition. The motor speed reduces as the torque increases causing a drooping characteristic. The speed-torque diagrams are presented below. These diagrams clearly demonstrate a speed reduction of 2 to 3% as the torque changes from no-load to full load.<\/p>\n<p>In DC motors, the armature MMF reacts to the field MMF. This behavior is introduced as the armature reaction. Once the effects of the armature reaction are removed, the flux per pole of the device is constant and is independent of power.<\/p>\n<p>In standard construction, the brushes are located in the neutral zone. The armature reaction, though cross magnetizing, can be resumed by demagnetization because of the saturation. The effect of demagnetization on the field because of the armature flux is too obvious and shown in the figure below. The speed reduction from no-load to full load reduces, improving speed control.<\/p>\n<figure id=\"attachment_8448\" aria-describedby=\"caption-attachment-8448\" style=\"width: 380px\" class=\"wp-caption aligncenter\"><img decoding=\"async\" class=\"size-full wp-image-8448\" src=\"https:\/\/www.linquip.com\/blog\/wp-content\/uploads\/2021\/05\/4-speed-vs-torque-Reference-electrical-tutorial.com_.png\" alt=\"Separately Excited DC Motor\" width=\"380\" height=\"302\" title=\"\" srcset=\"https:\/\/www.linquip.com\/blog\/wp-content\/uploads\/2021\/05\/4-speed-vs-torque-Reference-electrical-tutorial.com_.png 380w, https:\/\/www.linquip.com\/blog\/wp-content\/uploads\/2021\/05\/4-speed-vs-torque-Reference-electrical-tutorial.com_-300x238.png 300w\" sizes=\"(max-width: 380px) 100vw, 380px\" \/><figcaption id=\"caption-attachment-8448\" class=\"wp-caption-text\">Speed vs. Torque in a Separately Excited DC Motor (Reference: <strong>electrical-tutorial.com<\/strong>)<\/figcaption><\/figure>\n<p>The effect of external resistance in the armature circuit is presented in the figure below. Speeds in the level of zero to main speed may be achieved. With an appropriate amount of R, very slow speeds are feasible at the cost of efficiency.<\/p>\n<figure id=\"attachment_8449\" aria-describedby=\"caption-attachment-8449\" style=\"width: 372px\" class=\"wp-caption aligncenter\"><img decoding=\"async\" class=\"size-full wp-image-8449\" src=\"https:\/\/www.linquip.com\/blog\/wp-content\/uploads\/2021\/05\/5-speed-vs-torque-variable-resistance-Reference-electrical-tutorial.com_.png\" alt=\"Separately Excited DC Motor\" width=\"372\" height=\"278\" title=\"\" srcset=\"https:\/\/www.linquip.com\/blog\/wp-content\/uploads\/2021\/05\/5-speed-vs-torque-variable-resistance-Reference-electrical-tutorial.com_.png 372w, https:\/\/www.linquip.com\/blog\/wp-content\/uploads\/2021\/05\/5-speed-vs-torque-variable-resistance-Reference-electrical-tutorial.com_-300x224.png 300w, https:\/\/www.linquip.com\/blog\/wp-content\/uploads\/2021\/05\/5-speed-vs-torque-variable-resistance-Reference-electrical-tutorial.com_-80x60.png 80w, https:\/\/www.linquip.com\/blog\/wp-content\/uploads\/2021\/05\/5-speed-vs-torque-variable-resistance-Reference-electrical-tutorial.com_-160x120.png 160w, https:\/\/www.linquip.com\/blog\/wp-content\/uploads\/2021\/05\/5-speed-vs-torque-variable-resistance-Reference-electrical-tutorial.com_-265x198.png 265w\" sizes=\"(max-width: 372px) 100vw, 372px\" \/><figcaption id=\"caption-attachment-8449\" class=\"wp-caption-text\">Speed vs. Torque with Variable Resistance (Reference: <strong>electrical-tutorial.com<\/strong>)<\/figcaption><\/figure>\n<p>The speed-torque diagrams for a smooth change of the armature voltage are presented below. They move along the Y-axis (velocity axis) following variations in the armature voltage. The field winding of the device is supported by a separate supply.<\/p>\n<p>The smooth change of the armature voltage brings about speed adjustment in the zero to base speed level very efficiently. The device performs in a fixed torque mode. This method of sensing the speed of a separately excited DC motor employing variable voltage to the armature is used in different applications to control the amount of speed.<\/p>\n<figure id=\"attachment_8450\" aria-describedby=\"caption-attachment-8450\" style=\"width: 375px\" class=\"wp-caption aligncenter\"><img decoding=\"async\" class=\"size-full wp-image-8450\" src=\"https:\/\/www.linquip.com\/blog\/wp-content\/uploads\/2021\/05\/6-speed-vs-torque-variable-vlltage-Reference-electrical-tutorial.com_.png\" alt=\"Separately Excited DC Motor\" width=\"375\" height=\"298\" title=\"\" srcset=\"https:\/\/www.linquip.com\/blog\/wp-content\/uploads\/2021\/05\/6-speed-vs-torque-variable-vlltage-Reference-electrical-tutorial.com_.png 375w, https:\/\/www.linquip.com\/blog\/wp-content\/uploads\/2021\/05\/6-speed-vs-torque-variable-vlltage-Reference-electrical-tutorial.com_-300x238.png 300w\" sizes=\"(max-width: 375px) 100vw, 375px\" \/><figcaption id=\"caption-attachment-8450\" class=\"wp-caption-text\">Speed vs. Torque with Variable Voltage (Reference: <strong>electrical-tutorial.com<\/strong>)<\/figcaption><\/figure>\n<p>The effect of the field current change on the speed-torque feature is another method used for speed control. The field current is reduced to obtain speeds above the main speed when the armature voltage obtains its rated amount.<\/p>\n<p>The flux weakening mode is the best approach for constant power cases as the armature current may be maintained at its curtained amount. The torque also reduces in this mode. In the flux weakening method, the device cannot be utilized to drive fixed torque loads as the motor draws raised currents as the speed improves. This method is applied to achieve speeds in the range of base value to twice base one. The largest speed accessible by the flux weakening is restricted by commutation.<\/p>\n<p>The armature current can remain fixed in a full range of speeds from zero to twice base speed. The method used in this mode is feasible with shunt motors also through a variable amount of resistance in the field circuit.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Applications_of_Separately_Excited_DC_Motor\"><\/span><strong>Applications of Separately Excited DC Motor<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>A separately excited DC motor has industrial applications. It is typically used as an actuator. This form of motors is employed in trains and for automatic traction aims.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Download_separately_excited_dc_motor_PDF\"><\/span><strong>Download separately excited dc motor PDF<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n<div class=\"su-button-center\"><a href=\"https:\/\/www.linquip.com\/blog\/wp-content\/uploads\/2021\/08\/linquip.com-Separately-Excited-DC-Motor.pdf\" class=\"su-button su-button-style-default su-button-wide\" style=\"color:#FFFFFF;background-color:#2D89EF;border-color:#246ec0;border-radius:12px\" target=\"_blank\" rel=\"noopener noreferrer\"><span style=\"color:#FFFFFF;padding:0px 30px;font-size:22px;line-height:44px;border-color:#6cadf4;border-radius:12px;text-shadow:none\"> Download PDF<\/span><\/a><\/div>\n<h3><b>Buy Equipment or Ask for a Service<\/b><\/h3>\n<p>By using Linquip RFQ Service, you can expect\u00a0to receive quotations from various suppliers across multiple industries and regions.<\/p>\n<p style=\"text-align: center;\"><strong><a href=\"http:\/\/linquip.com\/get-quote?utm_source=blog&amp;utm_medium=content&amp;utm_campaign=product_list&amp;utm_term=product_list&amp;utm_content=rfq\" target=\"_blank\" rel=\"noopener\">Click Here to Request a Quotation From Suppliers and Service Providers<\/a><\/strong><\/p>\n<p>&nbsp;<\/p>\n<p><strong><span style=\"font-family: georgia, palatino, serif;\"><em>Read More In Linquip<\/em><\/span><\/strong><\/p>\n<ul>\n<li><span style=\"text-decoration: underline;\"><strong><span style=\"font-family: verdana, geneva, sans-serif;\"><span style=\"font-size: 10pt;\"><a href=\"https:\/\/www.linquip.com\/blog\/working-principle-of-dc-motor\/\" target=\"_blank\" rel=\"noopener\">Working Principle Of DC Motor: 2025 Complete Guide<\/a><\/span><\/span><\/strong><\/span><\/li>\n<li><span style=\"text-decoration: underline;\"><strong><span style=\"font-family: verdana, geneva, sans-serif;\"><span style=\"font-size: 10pt;\"><a href=\"https:\/\/www.linquip.com\/blog\/dc-motor-efficiency\/\" target=\"_blank\" rel=\"noopener\">DC Motor Efficiency: Calculation: Formula &amp; Equation<\/a><\/span><\/span><\/strong><\/span><\/li>\n<li><span style=\"text-decoration: underline;\"><strong><span style=\"font-family: verdana, geneva, sans-serif;\"><span style=\"font-size: 10pt;\"><a href=\"https:\/\/www.linquip.com\/blog\/series-wound-dc-motor\/\" target=\"_blank\" rel=\"noopener\">What is a Series Wound DC Motor?<\/a><\/span><\/span><\/strong><\/span><\/li>\n<li><span style=\"text-decoration: underline;\"><strong><span style=\"font-family: verdana, geneva, sans-serif;\"><span style=\"font-size: 10pt;\"><a href=\"https:\/\/www.linquip.com\/blog\/dc-motors-vs-servo-motors\/\" target=\"_blank\" rel=\"noopener\">DC Motors vs Servo Motors: A Complete Comparison<\/a><\/span><\/span><\/strong><\/span><\/li>\n<li><span style=\"text-decoration: underline;\"><strong><span style=\"font-family: verdana, geneva, sans-serif;\"><span style=\"font-size: 10pt;\"><a href=\"https:\/\/www.linquip.com\/blog\/separately-excited-dc-motor\/\" target=\"_blank\" rel=\"noopener\">Separately Excited DC Motor<\/a><\/span><\/span><\/strong><\/span><\/li>\n<li><span style=\"text-decoration: underline;\"><strong><span style=\"font-family: verdana, geneva, sans-serif;\"><span style=\"font-size: 10pt;\"><a href=\"https:\/\/www.linquip.com\/blog\/difference-between-dc-motor-and-stepper-motor\/\" target=\"_blank\" rel=\"noopener\">The Difference Between DC Motor and Stepper Motor: Everything You Need To Know<\/a><\/span><\/span><\/strong><\/span><\/li>\n<li><span style=\"text-decoration: underline;\"><strong><span style=\"font-family: verdana, geneva, sans-serif;\"><span style=\"font-size: 10pt;\"><a href=\"https:\/\/www.linquip.com\/blog\/what-is-universal-motor\/\" target=\"_blank\" rel=\"noopener\">Universal Motor: a Simple Guide to Construction, Types and Working<\/a><\/span><\/span><\/strong><\/span><\/li>\n<li><span style=\"text-decoration: underline;\"><strong><span style=\"font-family: verdana, geneva, sans-serif;\"><span style=\"font-size: 10pt;\"><a href=\"https:\/\/www.linquip.com\/blog\/advantages-of-dc-over-ac\/\" target=\"_blank\" rel=\"noopener\">What are the Advantages of DC over AC?<\/a><\/span><\/span><\/strong><\/span><\/li>\n<li><span style=\"text-decoration: underline;\"><strong><span style=\"font-family: verdana, geneva, sans-serif;\"><span style=\"font-size: 10pt;\"><a href=\"https:\/\/www.linquip.com\/blog\/difference-between-stepper-motor-and-dc-motor\/\" target=\"_blank\" rel=\"noopener\">A complete Guide to The Difference Between Stepper Motor and DC Motor<\/a><\/span><\/span><\/strong><\/span><\/li>\n<li><span style=\"text-decoration: underline;\"><strong><span style=\"font-family: verdana, geneva, sans-serif;\"><span style=\"font-size: 10pt;\"><a href=\"https:\/\/www.linquip.com\/blog\/dc-motor-working-principles\/\" target=\"_blank\" rel=\"noopener\">DC Motor Working Principles : The Most Compendious Reference<\/a><\/span><\/span><\/strong><\/span><\/li>\n<li><span style=\"text-decoration: underline;\"><strong><span style=\"font-family: verdana, geneva, sans-serif;\"><span style=\"font-size: 10pt;\"><a href=\"https:\/\/www.linquip.com\/blog\/compound-dc-motors\/\" target=\"_blank\" rel=\"noopener\">Compound DC Motors: Everything You Should Know About DC Compound Motors<\/a><\/span><\/span><\/strong><\/span><\/li>\n<li><span style=\"text-decoration: underline;\"><strong><span style=\"font-family: verdana, geneva, sans-serif;\"><span style=\"font-size: 10pt;\"><a href=\"https:\/\/www.linquip.com\/blog\/dc-motor-types\/\" target=\"_blank\" rel=\"noopener\">4 Different DC Motor Types and Their Applications<\/a><\/span><\/span><\/strong><\/span><\/li>\n<li><span style=\"text-decoration: underline;\"><strong><span style=\"font-family: verdana, geneva, sans-serif;\"><span style=\"font-size: 10pt;\"><a href=\"https:\/\/www.linquip.com\/blog\/shunt-dc-motors\/\" target=\"_blank\" rel=\"noopener\">Shunt DC Motors: An Easy-to-Understand Explanation of Working Principle and Components<\/a><\/span><\/span><\/strong><\/span><\/li>\n<li><span style=\"text-decoration: underline;\"><strong><span style=\"font-family: verdana, geneva, sans-serif;\"><span style=\"font-size: 10pt;\"><a href=\"https:\/\/www.linquip.com\/blog\/brushed-dc-motor\/\" target=\"_blank\" rel=\"noopener\">Brushed DC Motor: A Comprehensive Explanation of Working Principle, Parts, and Types<\/a><\/span><\/span><\/strong><\/span><\/li>\n<li><span style=\"text-decoration: underline;\"><strong><span style=\"font-size: 10pt;\"><a title=\"All About DC Motor Types and Their Applications\" href=\"https:\/\/www.linquip.com\/blog\/dc-motor-types\/\" target=\"_blank\" rel=\"noopener\">All About DC Motor Types and Their Applications<\/a><\/span><\/strong><\/span><\/li>\n<li><span style=\"text-decoration: underline;\"><strong><span style=\"font-size: 10pt;\"><a title=\"Shunt DC Motors: An Easy-to-Understand Explanation of Working Principle and Components\" href=\"https:\/\/www.linquip.com\/blog\/shunt-dc-motors\/\" target=\"_blank\" rel=\"noopener\">Shunt DC Motors: An Easy-to-Understand Explanation of Working Principle and Components<\/a><\/span><\/strong><\/span><span style=\"text-decoration: underline;\"><strong><span style=\"font-size: 10pt;\"><br \/>\n<\/span><\/strong><\/span><\/li>\n<li><span style=\"text-decoration: underline;\"><strong><span style=\"font-size: 10pt;\"><a title=\"Series Wound DC Motor\" href=\"https:\/\/www.linquip.com\/blog\/series-wound-dc-motor\/\" target=\"_blank\" rel=\"noopener\" data-schema-attribute=\"\">Series Wound DC Motor<\/a><\/span><\/strong><\/span><\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>What is a Separately Excited DC Motor? Like other motors, these devices also have both rotors and stators. Stator refers to the static section of the device, which contains the field windings. The rotor is the rotating armature which consists of armature coils or windings. A separately excited DC motor includes some field coils similar &#8230;<\/p>\n","protected":false},"author":10,"featured_media":8452,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"default","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","theme-transparent-header-meta":"default","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","footnotes":""},"categories":[12],"tags":[],"class_list":["post-8444","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-motor"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.linquip.com\/blog\/wp-json\/wp\/v2\/posts\/8444","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.linquip.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.linquip.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.linquip.com\/blog\/wp-json\/wp\/v2\/users\/10"}],"replies":[{"embeddable":true,"href":"https:\/\/www.linquip.com\/blog\/wp-json\/wp\/v2\/comments?post=8444"}],"version-history":[{"count":7,"href":"https:\/\/www.linquip.com\/blog\/wp-json\/wp\/v2\/posts\/8444\/revisions"}],"predecessor-version":[{"id":36622,"href":"https:\/\/www.linquip.com\/blog\/wp-json\/wp\/v2\/posts\/8444\/revisions\/36622"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.linquip.com\/blog\/wp-json\/wp\/v2\/media\/8452"}],"wp:attachment":[{"href":"https:\/\/www.linquip.com\/blog\/wp-json\/wp\/v2\/media?parent=8444"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.linquip.com\/blog\/wp-json\/wp\/v2\/categories?post=8444"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.linquip.com\/blog\/wp-json\/wp\/v2\/tags?post=8444"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}