CONTROL OF ELECTRIC MOTORS

Reversible Drives using Choppers

Reversible Drives using Choppers: Using two quadrant choppers a reversible drive can be achieved, because this combination allows reversal of both current and voltage of the motor termi­nals. We can get a regenerative reversible drive. The motor can operate in all four quadrants. A scheme of a Reversible Drives using Choppers is shown in Fig. […]

Reversible Drive using Field Reversal

Reversible Drive using Field Reversal: A Reversible Drive using Field Reversal can be realised as shown in Figs. 4.83 and 4.84. In Fig. 4.83, the armature is fed from a two quadrant converter with change over mechanical contactors in the field, which is also fed from a two quadrant converter. In the process of reversal […]

Reversible Drive using Dual Converter

Reversible Drive using Dual Converter: It is possible to reverse both voltage and current of the load using a dual converter. The current reversal is very fast in this case as the system is static without the mechanical output. A Reversible Drive using Dual Converter can be operated in either circulating current mode or circulating […]

Reversible Drive using Armature Current Reversal

Reversible Drive using Armature Current Reversal: A schematic of a reversible drive using contactors to reverse the Armature Current Reversal for reversing the rotation is shown kin Fig. 4.81. The contactors F1 and F2 are provided for rotation in the forward direction, whereas R1 and R2 in the reverse direction. This arrangement reverses the current in […]

Reversible Drives using Phase Controlled Converters

Reversible Drives: When speed control in both forward and reverse directions is required a Reversible Drives is used. In several applications the speed reversal may be required very frequently in which case a regenerative reversal may be advantageous. The drive is very efficient as the kinetic energy of rotating parts is returned to the supply. […]

Chopper Fed DC Drives

Chopper Fed DC Drives: The variable voltage to the armature of a dc motor for speed control can be obtained from a dc chopper which is a single stage dc to dc conversion device. The voltage variation at the load terminals can be obtained by using either current limit control or time ratio control. In […]

Methods to Leading Power Factor

Methods to Leading Power Factor: We have seen that a phase controlled converter requires reactive power for control and commutation. The harmonics do not contribute to the active power loading but they contribute to the reactive loading of the line. Because of these the line power factor is poor. A semi converter has been found […]

Three Phase Drives

Three Phase Drives: Single phase drives discussed in the previous section are employed for low and medium powers. When the power of the drive is very large the three-phase converter is preferred for supplying the load. As has been described early that increase in the number of pulses of the output voltage improves the performance. […]

Single Phase DC Series Motor Drives

Single Phase DC Series Motor Drives: In the Single Phase DC Series Motor Drives the field is connected in series with the armature. The field current is the same as the armature current. The schematic of a Single Phase DC Series Motor Drives fed from a phase controlled converter is shown in Fig. 4.62. DC […]

Single Phase Separately Excited DC Motor Drives

Single Phase Separately Excited DC Motor Drives: The circuit arrangement of a Single Phase Separately Excited DC Motor Drives Drives fed from a single phase controlled converter is shown in Fig. 4.56. The block 1 can be any one of the single phase converters. Half wave drives: The Single Phase Separately Excited DC Motor Drives […]

Commutation in DC Motor

Commutation in DC Motor: Commutation and commutator wear and tear of the dc motor must be given due consideration when the motor operates on solid state converters. Spark-less commutation must be aimed at. The reactance voltage and dynamically induced voltage in the coil undergoing commutation affect the rate of change of current in the coil. […]

Performance of DC Motors Operating on Phase Controlled Converters

Performance of DC Motors Operating on Phase Controlled Converters: The nature of the output voltage and output current of a phase controlled converters impains the performance of the dc motor operating on these con­verters. The output of the converter is in the form of pulses. The average voltage is superimposed by an ac ripple which […]

DC Motor Basic Machine Equation

DC Motor Basic Machine Equation: When dc voltage is applied to the armature of a dc motor with its field excited by dc, a torque is developed and the armature rotates. It accelerates to a speed at which the emf induced in the armature conductors balances the applied voltage and the following DC Motor Basic […]

Starting Methods of Synchronous Motor for LCI

Starting Methods of Synchronous Motor for LCI: It has been pointed out that a Starting Methods of Synchronous Motor for LCI, even though complicated in its construction, has an advantage that it can provide the necessary reactive power required by the inverter, except at low speed. Among all the drives possible with synchronous motor, Starting […]

Current Source Inverter with Forced Commutation

Current Source Inverter with Forced Commutation: Current Source Inverter with Forced Commutation – As has already been discussed, the disadvantages of machine commutation are (a) limitation on the speed range (b) the machine size is large and due to overexcitation it is underutilised. CSI with individual commutation for feeding synchronous motor. 1.used for providing commutation […]

Current Source Inverter Fed Synchronous Motor Drive

Current Source Inverter Fed Synchronous Motor Drive: A synchronous motor draws a stator current which is independent of stator frequency when V/f and E/f are maintained constant and armature resistance is neglected. The motor also develops constant torque. The flux also remains constant. Therefore, by controlling the stator current of a synchronous motor we can […]

Three Phase Synchronous Motor Fed From Cycloconverter

Three Phase Synchronous Motor Fed From Cycloconverter: DC link converter is a two stage conversion device which provides a variable voltage, variable frequency supply. Variable voltage, variable frequency sup­ply can be obtained from a cycloconverter which is a single stage conversion equipment. The power circuit of a Three Phase Synchronous Motor Fed From Cycloconverter is […]

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