Dead-time distortion - Revision history

Tero K: Text replacement - "{{param|PWM}}" to "PWM"

2015-08-28T19:55:37Z

Text replacement - "{{param|PWM}}" to "PWM"

Tero K: Text replacement - "\[\[([A-Z]{2,3})\]\]" to "{{param|$1}}"

2015-08-28T19:53:06Z

Text replacement - "\[\[([A-Z]{2,3})\]\]" to "{{param|$1}}"

Tero K at 20:21, 13 August 2013

2013-08-13T20:21:48Z

Tero K at 20:21, 13 August 2013

2013-08-13T20:21:35Z

Tero K at 21:24, 24 June 2013

2013-06-24T21:24:55Z

Tero K at 16:12, 24 March 2013

2013-03-24T16:12:31Z

Tero K: image to lfet

2012-06-25T16:03:31Z

image to lfet

Tero K: changed to multiple image template

2012-06-24T20:29:55Z

changed to multiple image template

Tero K at 20:25, 24 June 2012

2012-06-24T20:25:52Z

WikiAdmin at 12:18, 3 May 2012

2012-05-03T12:18:36Z

@@ Line 1: / Line 1: @@
-Dead time distortion (DTD) is a type of cross-over distortion caused by dead-time state of PWM power stages. The problem is present in all {{param|PWM}} output drives. The longer dead time used, the more significant distortion becomes.
+Dead time distortion (DTD) is a type of cross-over distortion caused by dead-time state of PWM power stages. The problem is present in all [[PWM]] output drives. The longer dead time used, the more significant distortion becomes.
 ==About dead-time==
 Dead-time is a blanking time period (upper & lower transistors in off-state simultaneously) of half-bridge power stage. Both transistors are switched off for short period of time to prevent both transistors conducting simultaneously thus causing a short circuit from supply to ground.
@@ Line 44: / Line 44: @@
 ===Dead time distortion===
-These graphs show actual distortion on sinusoidal motor currents when {{param|PWM}} frequency was 17.5 kHz and dead-time length 2 µs. No countermeasures were taken to reduce distortion.
+These graphs show actual distortion on sinusoidal motor currents when [[PWM]] frequency was 17.5 kHz and dead-time length 2 µs. No countermeasures were taken to reduce distortion.
 Notice the current dips in otherwise sinusoidal signal. There are 6 dips per sine cycle because in this experiment the test was done on a 3 phase motor which has 3 sine currents with 60 degree phase angle differences. Only one phase is displayed but distortion of two remaining phases will induce dips also in the neighbor phases.

@@ Line 1: / Line 1: @@
-Dead time distortion (DTD) is a type of cross-over distortion caused by dead-time state of PWM power stages. The problem is present in all [[PWM]] output drives. The longer dead time used, the more significant distortion becomes.
+Dead time distortion (DTD) is a type of cross-over distortion caused by dead-time state of PWM power stages. The problem is present in all {{param|PWM}} output drives. The longer dead time used, the more significant distortion becomes.
 ==About dead-time==
 Dead-time is a blanking time period (upper & lower transistors in off-state simultaneously) of half-bridge power stage. Both transistors are switched off for short period of time to prevent both transistors conducting simultaneously thus causing a short circuit from supply to ground.
@@ Line 44: / Line 44: @@
 ===Dead time distortion===
-These graphs show actual distortion on sinusoidal motor currents when [[PWM]] frequency was 17.5 kHz and dead-time length 2 µs. No countermeasures were taken to reduce distortion.
+These graphs show actual distortion on sinusoidal motor currents when {{param|PWM}} frequency was 17.5 kHz and dead-time length 2 µs. No countermeasures were taken to reduce distortion.
 Notice the current dips in otherwise sinusoidal signal. There are 6 dips per sine cycle because in this experiment the test was done on a 3 phase motor which has 3 sine currents with 60 degree phase angle differences. Only one phase is displayed but distortion of two remaining phases will induce dips also in the neighbor phases.

← Older revision		Revision as of 20:21, 13 August 2013
Line 54:		Line 54:
	[[Category:Technology]]		[[Category:Technology]]
	[[Category:Glossary]]		[[Category:Glossary]]
		+	[[Category:Argon features]]

@@ Line 53: / Line 53: @@
 The bottom image shows the exactly same experiment with the one above but this time [[Argon (servo drive)]] dead time correction was turned on. Notice how dips almost completely disappear and PWM duty cycle setpoint shows more sine-like waveform.
 [[Category:Technology]]
 [[Category:Glossary]]

@@ Line 9: / Line 9: @@
 Description of the image:
 # Schematic: typical single phase half-bridge PWM power output consisting two transistors and an inductive load (inductor). In 3 phase motor drives there are 3 pcs of this kind of circuits excluding inductor (which is replaced by a motor coil).
-# Desired load voltage waveform: the distortion free waveform [[Reference signal|reference signal]] on load that we would want to see.
+# Desired load voltage waveform: the distortion free waveform [[setpoint signal]] on load that we would want to see.
 # PWM to top transistor: PWM signal that is controls when the top side transistor is in conductive state.
 # PWM to bottom transistor: PWM signal that is controls when the bottom side transistor is in conductive state.
@@ Line 19: / Line 19: @@
 ==Distortion effects==
-[[File:Torqueripple w deadtime distortion.png|300px|thumb|Measured torque ripple as function of time when motor is rotating. Torque [[Reference signal|reference]] was constant so in ideal case this curve would be flat but instead it shows significant drops in torque periodically. No DTD distortion correction was used.]]
+[[File:Torqueripple w deadtime distortion.png|300px|thumb|Measured torque ripple as function of time when motor is rotating. Torque [[setpoint signal|setpoint]] was constant so in ideal case this curve would be flat but instead it shows significant drops in torque periodically. No DTD distortion correction was used.]]
 Some of most notable motion control problems caused by DTD:
 * Unwanted ripple in torque that may reduce motion smoothness
@@ Line 36: / Line 36: @@
 | image1    = Currentripple w deadtime distortion.png
 | alt1      = Before dead time correction
-| caption1  = No distortion correction. Top graph: phase current reference and achieved current. Bottom graph: PWM duty cycle reference
+| caption1  = No distortion correction. Top graph: phase current setpoint and achieved current. Bottom graph: PWM duty cycle setpoint
 | image2    = Currentripple w deadtime correction2.png
 | alt2      = After dead time correction
-| caption2  = [[Argon (servo drive)]] distortion correction enabled. Top graph: phase current reference and achieved current. Bottom graph: PWM duty cycle reference
+| caption2  = [[Argon (servo drive)]] distortion correction enabled. Top graph: phase current setpoint and achieved current. Bottom graph: PWM duty cycle setpoint
 }}
 ===Dead time distortion===
@@ Line 48: / Line 48: @@
 Notice the current dips in otherwise sinusoidal signal. There are 6 dips per sine cycle because in this experiment the test was done on a 3 phase motor which has 3 sine currents with 60 degree phase angle differences. Only one phase is displayed but distortion of two remaining phases will induce dips also in the neighbor phases.
-Also notice how PWM duty cycle reference from drive [[Torque controller|torque/current controller]] jumps up/down trying to compensate dead time errors. However, no current controller alone is fast enough to completely eliminate current ripples.
+Also notice how PWM duty cycle setpoint from drive [[Torque controller|torque/current controller]] jumps up/down trying to compensate dead time errors. However, no current controller alone is fast enough to completely eliminate current ripples.
 ===Distortion elimination===
-The bottom image shows the exactly same experiment with the one above but this time [[Argon (servo drive)]] dead time correction was turned on. Notice how dips almost completely disappear and PWM duty cycle reference shows more sine-like waveform.
+The bottom image shows the exactly same experiment with the one above but this time [[Argon (servo drive)]] dead time correction was turned on. Notice how dips almost completely disappear and PWM duty cycle setpoint shows more sine-like waveform.
 [[Category:Technology]]
 [[Category:Drive features]]
 [[Category:Glossary]]

@@ Line 29: / Line 29: @@
 ==Measurements==
 {{multiple image
-| align     = right
+| align     = left
 | direction = vertical
 | width     = 300
@@ Line 37: / Line 36: @@
 | image1    = Currentripple w deadtime distortion.png
 | alt1      = Before dead time correction
-| caption1  = Distortion correction disabled. Top graph: phase current reference and achieved current. Bottom graph: PWM duty cycle reference
+| caption1  = No distortion correction. Top graph: phase current reference and achieved current. Bottom graph: PWM duty cycle reference
 | image2    = Currentripple w deadtime correction2.png
@@ Line 43: / Line 42: @@
 | caption2  = [[VSD-XR]] distortion correction enabled. Top graph: phase current reference and achieved current. Bottom graph: PWM duty cycle reference
 }}
 These graphs show actual distortion on sinusoidal motor currents when [[PWM]] frequency was 17.5 kHz and dead-time length 2 µs. No countermeasures were taken to reduce distortion.

← Older revision		Revision as of 12:18, 3 May 2012
Line 42:		Line 42:
	[[Category:Technology]]		[[Category:Technology]]
	[[Category:Drive features]]		[[Category:Drive features]]
		+	[[Category:Glossary]]