Lab 5-2 Video System Troubleshooting Copyright 2006 Heathkit Company, Inc. All Rights Reserved
AC Power Quality and Protection 2
Today we will look at... AC Line Surge Suppressors Phone Line Surge Suppressors Power Conditioners (Line Conditioners) Backup Power Supplies 3
Protection against 4
Power Surge Surge is an over-voltage voltage lasting from about 8 ms to several seconds. Spike is a very short surge of less than 8 ms. Over-voltagevoltage > 140 VAC. 5
Power Noise Random fluctuations or electrical impulses carried by the AC waveform. Created by EMI and RFI sources. 6
Over-Voltage Over-voltagevoltage > 140 VAC Underwriters Lab has established 330 VAC as the maximum short-term term over- voltage. A lightening strike on a power grid is an extreme example of Over-Voltage. 7
Under-Voltage Under-voltage < 87 VAC Brown-out 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. 8
AC Line Protection Equipment 9
AC Line Surge Suppressors 10
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. 11
Surge Suppressor Problem #1 How much voltage do you allow to pass through before shunting it to ground? 120V, 330V, 400V, 600V? 12
Surge Suppressor Problem #2 After the surge suppressor shunts a very high voltage to ground, it dies. 13
AC Line Surge Suppressors What to look for when buying an AC line surge suppressor. 14
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. 15
AC Line Surge Suppressors What prevents a surge suppressor from working properly? 16
What prevents a surge suppressor from working properly? To what type of AC network is the computer connected? 17
Phone Line Surge Suppressors 18
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 20
Power Conditioners Also called Line Conditioners Suppress high voltage spikes and surges on both the AC line and the telephone line Filter out electrical noise RFI and EMI Regulates AC voltage 21
Power Conditioners Boost under-voltage conditions Reduce over-voltage voltage conditions Stable 120-VAC nominal output Requires an input to produce an output 22
Backup Power Supplies 23
Backup Power Supply Definition: A backup power supply provides power to a PC during an under-voltage condition or complete power blackout to give a user time to safely save their work and shut down. 24
Backup Power Supply Common name is Uninterruptible Power Supply (UPS) Several different types available to meet different computer needs. Off-line and on-line protection. Practical power ranges from 0 to 1 mva. 25
Standby UPS Off-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. 26
Standby UPS Under normal conditions, the AC line powers the computer and charges the battery. Standby UPS Battery Charger Battery DC-to-AC Inverter AC Line In Sensor AC Line Out 27
Standby UPS During a power outage the AC line sensor switches-in in the battery and DC-to-AC inverter to power the computer. Standby UPS Battery Charger Battery DC-to-AC Inverter AC Line In Sensor AC Line Out 28
Standby UPS Practical power range 0 to 500 VA Low degree of line voltage conditioning Low cost per volt-amp Very high efficiency design, inverter only operates when it is needed Adequate switching times 29
On-Line UPS Line interactive power source. Provides complete power conditioning. Uses batteries as backup power source. Voltage Inverter converts the battery DC voltage to AC voltage. The PC runs off the UPS inverter all the time. 30
Line Interactive UPS Primary and secondary power passes through the inverter, so no switching is required. Line Interactive UPS AC Line In Sensor Battery DC-to-AC Inverter AC Line Out 31
Line Interactive UPS When AC power is interrupted, the UPS continues to power the PC with its battery. Line Interactive UPS AC Line In Sensor Battery DC-to-AC Inverter AC Line Out 32
Line Interactive UPS Practical power range 500 to 3000 VA High degree of power conditioning Medium cost per volt-amp Very high efficiency design Instantaneous switching times 33
Now, it s your turn.