A common 400 Hz AC Power Supply Distribution System
for CMS FEE.
AuthorsC. Rivetta– Fermilab.
F. Arteche , F. Szoncso, - CERN
A common 400 Hz AC Power Supply Distribution System for CMS FEE.– 2 / 19
8th Workshop on Electronics for LHC ExperimentsCOLMAR - France, 9-13 September 2002
OUTLINE
1- System Description 2- Design - General Guidelines 3- Voltage Disturbances
–Steady State - Voltage Regulation–Steady State - Harmonics–Transient Voltage Disturbances–Voltage Sources
4- Over current protections 5- Grounding 6- Conclusions
A common 400 Hz AC Power Supply Distribution System for CMS FEE.– 3 / 19
8th Workshop on Electronics for LHC ExperimentsCOLMAR - France, 9-13 September 2002
1.SYSTEM DESCRIPTION
M-Gs convert 50 Hz mains to 400 Hz - 208 V - 3 phase Sub-detectors will be supplied by individual units. 3-phase distribution system between counting room and
periphery of the detector. Sub-detectors have proposed 2 different conversion units:
– Simple 3-phase rectifiers-filters & LV regulators– AC/DC conversion to 48V DC & DC-DC converters
3 phase rectifiers-filters & DC-DC converters will operate under neutron radiation and fringe magnetic fields.
A common 400 Hz AC Power Supply Distribution System for CMS FEE.– 4 / 19
8th Workshop on Electronics for LHC ExperimentsCOLMAR - France, 9-13 September 2002
1.SYSTEM DESCRIPTION400Hz Distribution at CMS
• Topology – Based on HCAL/EMU systems
150mts. 10-20mts.
MG-Yo Distr.Panel
AC-DC
AC-DC
AC-DC
208V/400Hz
Area 3Area 2
Area 1
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8th Workshop on Electronics for LHC ExperimentsCOLMAR - France, 9-13 September 2002
2.DESIGN - GENERAL GUIDELINES
Power quality distribution – Amplitude variations
Several forms - Duration: sub-cycle to steady state
– Waveform variations Distortion
– Unbalances No single-phase loads
– Frequency variations Characterisation of loads
-Characterisation of the environment.
IEEE Std 1100 - 1992
A common 400 Hz AC Power Supply Distribution System for CMS FEE.– 6 / 19
8th Workshop on Electronics for LHC ExperimentsCOLMAR - France, 9-13 September 2002
3.1 STEADY STATE VOLTAGE DISTURBANCE - VOLTAGE REGULATION
Distribution cable impedance much higher than 50 / 60 Hz– Non-ferrous conduits .– 400Hz especial cables.– Impedance drops up to
AWG #1 / 54mm2
Voltage drop in transformers and generators.– Generator can operate with
closed loop voltage regulators.
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8th Workshop on Electronics for LHC ExperimentsCOLMAR - France, 9-13 September 2002
3.1 STEADY STATE VOLTAGE DISTURBANCE VOLTAGE REGULATION - EXAMPLE
Group of loads
AWG 6 / 13,3mm2
AWG 8
8,36mm2
5mts 100mts 20mts
P1P2
+5%
P2 Load
+5%
Vn
-5%
No load
Full load
Gen P1
Vn
-5%
No load
Full load
P2 Load
A common 400 Hz AC Power Supply Distribution System for CMS FEE.– 8 / 19
8th Workshop on Electronics for LHC ExperimentsCOLMAR - France, 9-13 September 2002
3.2 STEADY STATE VOLTAGE DISTURBANCE HARMONIC DISTORTION
All CMS loads connected to the 400 Hz. system are non linear.– Generate harmonics current.
Harmonics currents imply:– Over-rating. – Voltage distortion
400 Hz. harmonic effects are more severe than 50/60 Hz. Voltage generators and static converters can produce good
quality sine waves - THD 3% Current harmonics can be reduced by filtering /compensation
or imposing restrictions to the load harmonics generation.
A common 400 Hz AC Power Supply Distribution System for CMS FEE.– 9 / 19
8th Workshop on Electronics for LHC ExperimentsCOLMAR - France, 9-13 September 2002
3.2 STEADY STATE VOLTAGE DISTURBANCE HARMONIC DISTORTION Loads are qualified by harmonic indices
– Strongly correlated to the severity of the harmonics effects. Recommended harmonics indices are :
– Individual and total voltage distortion .– Individual and total current distortion.
Standards define limits based:– On loads size.– Characteristics of load groups.
Examples– Dedicated system:
Maximum individual frequency voltage harmonic = 2.5 / 3 % Maximum individual frequency current harmonic - Lower 4 %
A common 400 Hz AC Power Supply Distribution System for CMS FEE.– 10 / 19
8th Workshop on Electronics for LHC ExperimentsCOLMAR - France, 9-13 September 2002
3.2 STEADY STATE VOLTAGE DISTURBANCE HARMONIC DISTORTION - Example - A
I1 I2
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8th Workshop on Electronics for LHC ExperimentsCOLMAR - France, 9-13 September 2002
3.2 STEADY STATE VOLTAGE DISTURBANCE HARMONIC DISTORTION - Example A
In : one power converter Vn: 15 power converters /100mts AWG#8 - 13.3mm2
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8th Workshop on Electronics for LHC ExperimentsCOLMAR - France, 9-13 September 2002
3.2 STEADY STATE VOLTAGE DISTURBANCE HARMONIC DISTORTION - Example B
A common 400 Hz AC Power Supply Distribution System for CMS FEE.– 13 / 19
8th Workshop on Electronics for LHC ExperimentsCOLMAR - France, 9-13 September 2002
3.2 STEADY STATE VOLTAGE DISTURBANCE HARMONIC DISTORTION - Example B
In : one power converter Vn: 15 power converters /100mts AWG#8 - 13.3mm2
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8th Workshop on Electronics for LHC ExperimentsCOLMAR - France, 9-13 September 2002
3.3 TRANSIENT VOLTAGE DISTURBANCE Load related changes & switching events cause disturbances
between equipment and power source– Step loads.– In-rush currents.
Origin: Start-up transformers & Rectifiers with capacitive filters– Faults currents.
Origin: Short-circuit faults. Long duration: Several cycles of fundamental wave form. Impact :
– Complete loss of AC power.– Short term voltage variation.– Data up-set.
Design criteria– Reduce the transient energy ( Start-up systems, load sectioning..)
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8th Workshop on Electronics for LHC ExperimentsCOLMAR - France, 9-13 September 2002
3.4 VOLTAGE SURGES
Switching surges– Originated by fuses, circuit breakers and switches – Wave form - Fast rise time followed by damped oscillation
Sub-cycle voltage transients Impact depends on the severity of the transient and
equipment susceptibility.– Signal data disruption – Gradual hardware stress – Immediate hardware destruction
Design criteria– Transients voltage supressors in distribution system and
equipment
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8th Workshop on Electronics for LHC ExperimentsCOLMAR - France, 9-13 September 2002
4 OVER CURRENT PROTECTIONS
Appropriated co-ordination of current protections– Rating & Clearing Timing
50 / 60 Hz components has to be properly de-rated for 400Hz applications– Fuses are not appreciably affected – Thermal-Magnetic & Magnetic circuit breakers are
affected Magnetic circuit breakers & switchers must be
excluded from areas where exist magnetic field
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8th Workshop on Electronics for LHC ExperimentsCOLMAR - France, 9-13 September 2002
5 GROUNDING
Grounding is essential for safe and satisfactory performance of the complete system.
Characteristics – Low impedance path for the return of fault currents.– Low potential difference between expose metal parts to
avoid personal hazards. – Over-voltage control on sensitive electronics.– Should be compatible with the system performance and
noise, without compromising safety The grounding of the distribution system will follow the
general grounding rules imposed to CMS experiment
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8th Workshop on Electronics for LHC ExperimentsCOLMAR - France, 9-13 September 2002
5 GROUNDING
SENSITIVE LOAD
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8th Workshop on Electronics for LHC ExperimentsCOLMAR - France, 9-13 September 2002
6 CONCLUSIONS
Design considerations for quality power distribution of the CMS 400Hz distribution has been presented.
Further considerations– Better understanding of the impact of environment conditions
on protections, load performance, etc.– Definition of final system topology.
Definition of specifications based on voltage quality wave form and system reliability– System design specifications– Load specifications (Sub-detectors)