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Motor Drives

The document discusses different operating modes of DC motors, including motoring, regenerative braking, dynamic braking, and plugging. It then covers single-phase DC motor drives that can operate the motor in different quadrants by changing the firing angle (α) to vary the supply voltage (Va) and field voltage (Vf). Single-phase half-wave, semiconverter, and full-converter drives are compared in terms of the quadrants they can operate in and their output voltage waveforms.

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Abir Lovesick
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86 views21 pages

Motor Drives

The document discusses different operating modes of DC motors, including motoring, regenerative braking, dynamic braking, and plugging. It then covers single-phase DC motor drives that can operate the motor in different quadrants by changing the firing angle (α) to vary the supply voltage (Va) and field voltage (Vf). Single-phase half-wave, semiconverter, and full-converter drives are compared in terms of the quadrants they can operate in and their output voltage waveforms.

Uploaded by

Abir Lovesick
Copyright
© Attribution Non-Commercial (BY-NC)
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
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DC Motor Drives

How a DC Motor Works

How a DC Motor Works

Brushes

F = IL B

Operating Modes
In variable-speed applications, a dc motor may be operating in one or more of the following Modes Motoring Regenerative braking Dynamic braking Plugging

Motoring Mode

Back emf, Eg is < supply voltage Va Both Ia and If are positive Developed torque meets load demand

Regenerative Braking Mode

Motor acts as a Generator Eg becomes > supply Voltage Va Ia becomes negative Kinetic energy of the motor is returned to the supply

Dynamic Braking

Replace the supply voltage with a resistor Power dissipated in the resistor rather than given back to the source

Plugging

Reverse the armature terminals while running Va and Eg act in the same direction Ia is reversed, producing braking torque

Four-Quadrant Operation

Single-Phase DC Drive

Change Va by changing firing angle Inductor Lm is a smoothing Inductor to prevent discontinuous current

Armature Reversal

Field Reversal

Single-Phase Half-Wave Converter Drive

Va =

Vm (1 + cos a ) 2 0 a Vm

Vf =

0f

(1 + cos f )

Quadrant of Operation

Waveform Summary

Single-Phase Semiconverter Drives

Va =

Vm

0 a Vf = Vm

(1 + cos a )

0 f

(1 + cos f )

Quadrant(s) of Operation

Semiconverter one quadrant converter One polarity of output voltage and current

Waveform Summary

Single-Phase Full-Converter Drives

Quadrant(s) of Operation

Full converter two quadrant converter Output voltage polarity can be positive or negative Output current has one polarity

Single-Phase Dual-Converter Drives

Dual converter can operate in all four quadrants Output voltage and current can be positive or negative

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