A common 400 Hz AC Power Supply Distribution System for CMS FEE. Authors C. Rivetta– Fermilab. F. Arteche, F. Szoncso, - CERN

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



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.



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



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



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.



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



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.



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 %



3.2 STEADY STATE VOLTAGE DISTURBANCE HARMONIC DISTORTION - Example - A

I1 I2



3.2 STEADY STATE VOLTAGE DISTURBANCE HARMONIC DISTORTION - Example A

In : one power converter Vn: 15 power converters /100mts AWG#8 - 13.3mm2



3.2 STEADY STATE VOLTAGE DISTURBANCE HARMONIC DISTORTION - Example B



3.2 STEADY STATE VOLTAGE DISTURBANCE HARMONIC DISTORTION - Example B

In : one power converter Vn: 15 power converters /100mts AWG#8 - 13.3mm2



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..)



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



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



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



5 GROUNDING

SENSITIVE LOAD



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)

Documents

A common 400 Hz AC Power Supply Distribution System for CMS FEE. Authors C. Rivetta– Fermilab. F. Arteche, F. Szoncso, - CERN