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Energy Basics > Electrical Power Systems > Flashcards

Electrical Power Systems Flashcards

1
Q

Most electrical loads are not pure resistive, and involve ____ (conversion to magnetic energt) which impactss the AC power system.
Reduces power factor

A

Inductive Loads

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2
Q

__ __ cause currents to be drawn that are not in phase with that of the applied voltage. The higher currents increase

A

Magnetic Loads

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3
Q

the __ currents increase the energy lost in the distribution system and require large wires and other equipment

A

higher

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4
Q

We seek to reduce the reactive power, which will reduce the apparent power and increase the __ __

kW / kVA

A

Power Factor

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5
Q

Power factors below __ __ require a utility to generate more than the minimum volt-amperes necessary to get the work done.

A

5%

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6
Q

Inserting a ___ to correct the power factor and need less apparent power you will need
kVAR needed = Real power (kW) - Table Factor

A

capacitor

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7
Q

Billed kW =

A

Metered kW * .9 over measured PF during month

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8
Q

__ __ is related to how well a bus voltage (usually our facility) maintains a pure sinusoidal waveform at rated voltage and frequency
Issues include - spikes, notches, outages, harmonics, and power factor

A

Power Quality

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9
Q

Voltage imbalance between three phases

A

Reduced motor efficiency, potential damage to motors, increased losses, increased neutral current

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10
Q

__ __ __ is found as the rate of the largest phase to phase voltage difference from average, divided by the average voltage
maximum deviation from average / average voltage

A

Percent voltage imbalance

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11
Q

steps to deal with power problems

A
  1. Inspect wiring and and grounding

2. clean and tighten all connection

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12
Q

Loose electrical connections come from what four things?

A

vibration, oxidation, corrosion, and age

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13
Q

multiples of the fundamental frequency

A

Harmonics

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14
Q

A measure of power quality
Limits are_
General systems - 5%
Special applications (hospitals MRI machines) - 3%

A

Total Harmonic Distortion (THD)

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15
Q

provides recommended practices and requirements for harmonic control in electrical power systems

A

IEE 519 Power Quality Standards

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16
Q

How to assess harmonics

A

Power Quality meters provide the ability to see what harmonics exist
Low order cause more power type issues
higher order cause more interference type issues

17
Q

p = V * I * PF (watts)

A

Single Phase AC system
Power = Volts - average phase to phase voltage * Ampere - average phase current (Volts) * power factor in watts (watts / Volt Amps)

18
Q

P = 1.732 * V * I * PF

A

Three-phase AC system
Power = square root of three * Volts - average phase to phase voltage * Ampere - average phase current (Volts) * power factor in watts (watts / Volt Amps)

19
Q

PF =
V =
I =

A

Power Factor
V - Volt - average phase to phase voltage
I - ampere or current

20
Q

kW (given electrical info) = 1.732 * kV * I (ampere) * PF (power factor)

kW (given mechanical info) = HPnameplate * .746kW/HP * LF OVER Efficiency

A

three phase motor equations

21
Q

kW

A

The real/working and useful power (work done)

22
Q

kVAR

A

reactive power, kilovoltamps reactive - we need some reactive power to create and maintain the magnetic field which rotates the motor

23
Q

kVA

A

Total apparent power
How much value for money we’re getting for the power we consume
kilovolt amperes

24
Q

In power factor management, we seek to __ the kVAR reactive power, which will __ the total apparent power and __ the power factor. The real working power remains __.

A

Reduce
Reduce
Increase
Unchanged

25
Q

Why is it bad to have a low Power factor and what is this number?

A

industrial plants are increasing the current flow through the electricity network and causing voltage drops which reduces the suppliers distribution capacity and has a knock on effect for other customers.
Below 1 is bad

26
Q

What are the formulas for Power Factor for a 3 phase motor

A

kW / kVa

kW / (kVI1.732)

27
Q

an expression of how much energy was used in a time period, versus how much energy would have been used, if the power had been left on during a period of peak demand. It is a useful indicator for describing the consumption characteristics of electricity over a period of time.

A

What is load factor?

28
Q

If a power factor correction capacity is installed on a motor, the power factor __ of the capacitor is increased.

The current (amps) upstream of the capacity is __

A

increased, decreased

29
Q

A facility has properly installed a power factor correction capacitor on a motor. The power factor upstream of the capacitor has been improved. What is the impact on the real (working) power used by the motor?

A

It is unchanged because the motor still does the same amount of work downstream.

Energy Basics (15 decks)

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