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High Resistance Materials Tables

May 5, 2008 in Electrical, Reference

Liquids

20 C	OHM	-M
	min	max
Benzene	10¹¹	10¹²
Transformer oil	10¹⁰	10¹³
Gasoline	10¹⁰	10¹³
Castor oil	10⁸	10¹⁰
Acetone	10⁴	10⁵
Ethanol	10⁴	10⁵
Distilled water	10³	10⁴

Glass At High Temperature

200 C	OHM -M
Sodium Pyrex	2 * 10⁶
Potassium Pyrex	8 * 10⁹
Lead glass	2 * 10¹¹

Effect Of Contamination On Surface Resistivity

70% RH	CONTAMINATED	CLEAN
Window glass	2 * 10⁸	10¹²
Fused quartz	2 * 10⁸	10¹³

Relation Of Resistivity With RH % And Temp

MATERIAL	70% RH 20 deg C	0% RH 100 deg C	0% RH 20 deg C
Marble	10^{6 -} 10⁸	10^{10 -} 10¹²	10^{12 -} 10¹⁴
Wood	10^{6 -} 10⁷	10^{10 -} 10¹²	10^{11 -} 10¹³
Vulcanized fibers fibers	10^{6 -} 10⁹	10^{8 -} 10⁹	10^{11 -} 10¹²
MATERIALS	SOLIDS OHM -M

Solids

MATERIALS	OHM -M
Polyethylene	10¹⁷
Poly propylene	10¹⁷
PVC	10¹⁸
Polyurethane	10¹⁵
Asbestos fiber + phenol	10⁸
Mica + phenol	10¹²
Glass-fiber + polyester	10¹²
Glass-fiber + epoxy	10¹⁴

UPS Power Inverter and DC to AC

March 13, 2008 in Electrical, Design and Development, Schematics

Standards

CBEMA - Computer Business Equipment Manufacturer’s Association
adopted curve IEEE Standard 446 (orange book) curve.

Recommended Practice for Emergency and Standby power systems for Industrial and Commercial Application.”

Wave form Sine wave THD (total harmonic distortion) maximum 5%.
3 Phase system phase imbalance of voltage 3% - 6%.
Frequency stability 60 (50 Hz in India) +/- 0.5Hz.
Output Voltage +6% Max. -13% Min. from Nominal Value.
Voltage can fall to 0V but should recover in 0.5 Cycles.
On turn on Voltage should reach steady state within two seconds.
Upto 200% over Nominal Voltage should be tolerated for 100uS. ( Transients, spikes and Inductive Kickbacks come in this)
Upto 30% over Nominal Voltage should be tolerated for 0.5S.

ANSI - American National Standards Institute

“Standard Voltage Ratings for Electrical power systems & Equipment”

Steady State Variations +/- 5% of Nominal Voltage. T
Three Phase Voltage Imbalance 5% Max..
Standard Frequency 60Hz.

Glossary

Frequency 60Hz Hz is Hertz.
One Cycle = 20mS (milliseconds) one full sine wave.
In India Standard Frequency is 50Hz.
Max - Maximum
Min - Minimum
uS - micro seconds, S - seconds.

Cause of Transients

Switching Loads Simultaneously (inductive loads).
Power factor correction capacitors and devices.
Lightning strikes (enhanced by earth faults).
Line Inductance (inductive kickback, resonance).
DC and AC Drives for Motors.
Rectifiers with large filters and stray inductance.

Extra Reading

UPS Inverter

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