5-2 Lab 5Video System Troubleshooting
Copyright 2006 Heathkit Company, Inc. All Rights Reserved
AC Power Quality and Protection
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Today we will look at...
AC Line Surge Suppressors Phone Line Surge Suppressors Power Conditioners (Line Conditioners) Backup Power Supplies
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Protection against...
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Power Surge
Surge is an over-voltage lasting from overabout 8 ms to several seconds. Spike is a very short surge of less than 8 ms. OverOver-voltage > 140 VAC.
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Power Noise
Random fluctuations or electrical impulses carried by the AC waveform. Created by EMI and RFI sources.
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Over-Voltage
OverOver-voltage > 140 VAC Underwriters Lab has established 330 VAC as the maximum short-term overshortovervoltage. A lightening strike on a power grid is an extreme example of Over-Voltage. Over7
Under-Voltage
UnderUnder-voltage < 87 VAC BrownBrown-out >87 VAC<100 VAC Caused by failure in the power grid. Caused by demand exceeding power grid capacity. Causes excessive currents in computer power supplies. Causes system crashes when power supply voltages do not meet requirements.
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AC Line Protection Equipment
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AC Line Surge Suppressors
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AC Line Surge Suppressors
Also called spike isolators. Use a MOV (Metal Oxide Varistor) to send spikes and surges to ground. Some use gas discharge tubes, pellet arrestors, or coaxial arrestors. They are far from ideal.
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Surge Suppressor Problem #1
How much voltage do you allow to pass through before shunting it to ground? 120V, 330V, 400V, 600V?
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Surge Suppressor Problem #2
After the surge suppressor shunts a very high voltage to ground, it dies.
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AC Line Surge Suppressors
What to look for when buying an AC line surge suppressor.
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What to look for when buying an AC Line Surge Suppressor...
Do not buy one without a light to indicate there was a surge that probably destroyed the MOV.
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AC Line Surge Suppressors
What prevents a surge suppressor from working properly?
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What prevents a surge suppressor from working properly?
To what type of AC network is the computer connected?
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Phone Line Surge Suppressors
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Phone Line Surge Suppressors
Phone Jacks (1 In/1 Out)
Protects against telephone line lightning strike surges. Built into a power line surge suppressor.
Power Conditioners
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Power Conditioners
Also called Line Conditioners Suppress high voltage spikes and surges on both the AC line and telephone the line Filter out electrical noise--RFI and EMI noise-- Regulates AC voltage
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Power Conditioners
Boost under-voltage conditions underReduce over-voltage conditions overStable 120-VAC nominal output 120Requires an input to produce an output
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Backup Power Supplies
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Backup Power Supply
Definition: A backup power supply provides power to a PC during an under-voltage condition or undercomplete power blackout to give a user time to safely save their work and shut down.
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Backup Power Supply
Common name is Uninterruptible Power Supply (UPS) Several different types available to meet different computer needs. OffOff-line and on-line onprotection.
Practical power ranges from 0 to 1 mVA.
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Standby UPS
OffOff-line power source. Batteries are continuously charged. When power is interrupted, batteries switch into the current path. Voltage Inverter converts the battery voltage to AC. Some AC power line conditioning may be provided.
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Standby UPS
Under normal conditions, the AC line powers the computer and charges the battery.
Standby UPS
Battery Charger AC Line In
Sensor Battery
DC-to-AC Inverter
AC Line Out
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Standby UPS
During a power outage the AC line sensor switchesswitches-in the battery and DC-to-AC inverter DC-toto power the computer. Standby UPS
Battery Charger AC Line In
Sensor Battery
DC-to-AC Inverter
AC Line Out
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Standby UPS
Practical power range 0 to 500 VA Low degree of li...