Experts in Power

Experts in Power Training Course

Power Sources (copy)

Power Sources Presented by Stephen Dodson

Explain how electricity is generated in a power station

Why do power stations generate 3 phase?

What range of standards deals with conducted immunity?

Input Protection (copy)

Input Protection Presented by Stephen Dodson

If it isn't field replaceable explain the reason for having an input fuse in a power supply

Explain how inrush current can be limited within the PSU and what issues are associated with this?

What are the two main types of circuit breaker?

What part of the circuit breaker spec must you take particular note of if you are using it in a battery application?

Name 3 methods/components which can help with transient voltage protection?

What two methods of reverse polarity protection can be employed on a DC/DC converter and what are the benefits and drawbacks of each?

Real & Apparent Power (copy)

Real & Apparent Power Presented by Les Chant

Which type of power delivers useful energy into the load, real or reactive?

What do we mean by the term ‘power factor’?

Does a capacitive load current lead or lag the voltage?

  • Lead
  • Lag

What effect do harmonics on a mains supply have on power factor?

Why is it ideal to have a high power factor in any system?

Harmonics (copy)

Harmonics Presented by Diana Izvorska

Explain in your own words how harmonics are generated by switch mode power supplies?

What does EN6100-3-2 talk about?

Why is harmonic distortion a problem?

What class of EN61000-3-2, do must of our power supplies meet? Example of Class C?

Explain one of the two possible passive power factor correction techniques?

Give some examples of the ranges of power supplies that utilise these?

In order to achieve active power factor correction we 'add' another power supply, what is this stage called?

Give two advantages and two disadvantages of active PFC?

Earthing (copy)

Earthing Presented by Stephen Dodson

Explain the difference between class 1 and class 2 protection systems?

Between which conductors would you find common mode noise?

Explain which components are used in the Differential Mode Filter.

Over what frequency range does the conducted emissions part of EN55022 cover?

What type of noise increases at high frequencies?

In your own words, what might you do to improve it?

Regulation (copy)

Regulation Presented by Les Chant

Explain, in your own words, line regulation?

Explain, in your own words, load regulation?

Explain how remote sense works, and what precautions must you take when using it?

Explain the effects of cross regulation?

What are the benefits of linear regulation?

Using the measurements for the JPS250PS24, calculate the load regulation at the load and the power supply connections, with and without the sense leads. Does the performance recorded match that described in the remote sense part of the presentation?

Is the performance measured in question 6 correct to the datasheet for JPS250PS24?

Output Protection & Ripple + Noise (copy)

Output Protection Presented by Stephen Dodson

Ripple + Noise Presented by Stephen Dodson

For which applications would you use a PSU with a constant current output?

Why is a Trip & Restart current limit popular?

Explain how a PTC fuse operates?

Why is it common for the OVP circuit to latch and not self recover?

Why is low frequency ripple at twice the line frequency?

Where would a periodic noise be prolific?

Explain the correct way to measure noise, and why?

How would you reduce switching frequency ripple?

How is ripple and noise specified, and why?

What issues may customers face because of high levels of ripple and noise?

Series + Parallel & Signals + Interfacing (copy)

Series + Parallel & Signals + Interfacing Presented by Les Chant

Name 3 different types of signal found on power supplies?

Explain, in your own words, how a power fail detect signal operates?

Explain the difference between an active high and an active low signal?

Name an XP product which has the current share control?

Explain the difference between TTL compatible signals and open collector signals?

Safety Basics (copy)

Safety Basics Presented by Diane Izvorska

What is the Primary IT safety standard used in Europe?

How many levels of protection are required to ensure a system is safe?

Explain Creepage?

Explain Clearance?

What are the production test voltages for basic insulation? and what determines this value?

Name two types of earthing that can be present in a system? What are the LOP's of each?

What is the insulation between the primary and secondary side of a power supply? and what is the LOP of this insulation?

What components are included in the thermal safety agency testing, and why?

List two approvals based on the CB scheme? which country are they for?

Explain what the CE marking is for? list two directives applicable for the PS?

Medical Safety (copy)

Medical Safety Presented by Diane Izvorska

What is the primary medical safety standard?

Describe the term "Patient Vicinity' as defined in the 3rd Edition?

Fully describe the term 'MOOP'?

Fully describe the term 'MOPP'?

What is the relationship between 'LOP' and 'MOP'?

What is the test voltage for Reinforced insulation for a medical device?

What is the maximum earth leakage current allowed in UL?

What are the 3 classifications of Applied Parts?

Explain the need for an extra isolation barrier in BF and CF applications?

Where would you find Patient Leakage Current?

Emissions & Immunity (copy)

Emissions & Immunity (Conducted & Radiated Noise) Presented by Stephen Dodson

Emissions & Immunity (Conducted & Radiated Immunity) Presented by Stephen Dodson

Describe ‘Peak Measurement’?

Describe ‘Average Measurement’?

Describe ‘Quasi Peak Measurement’?

Why do we normally use the peak measurement?

Name the 3 pieces of equipment necessary to perform the conducted emissions test?

Define the differences between Class A and Class B equipment?

Why can we not perform radiated emissions testing?

What immunity tests can we carry out at XP?

Why can’t we perform IEC61000-4-3?

Explain the difference between a ‘fast transient’ and a ‘surge’ pulse?

Reliability (copy)

Reliability Presented by Diane Izvorska

Name and describe the three regions of the bathtub curve?

Describe MTBF?

Describe MTTF?

What is the connection between service life and failure rate?

When designing a power supply, what factors must you consider to ensure reliability, and why?

What systems are used to estimate the failure rate, and why are they flawed?

What testing cold be done during prototype testing to help ensure the reliability of a power supply?

How is reliability manufactured into the product?

How does redundancy achieve increased reliability?

I want to compare two MTBF figures. One is a MIL-HDBK-217E calculation and one is HRD5. How do I go about this?

PSU Topologies (copy)

PSU Topologies Presented by Gary Bocock

Explain in your own words why we use isolated fly-back converters for lower power AC-DC power supplies?

Give four examples of where we use isolated fly-back converters?

Give two advantages of LLC converters?

Why is it important to use active power factor correction when implementing an LLC converter solution?

Green Mode Power (copy)

Green Mode Power Presented by Gary Bocock

What are the design aims of green mode power supplies?

What are the three topologies typically seen in green mode supplies?

Name three pieces of legislation regarding energy efficiency of power?

What are the four measurement points for active mode efficiency?

Name three potential side effects of green mode operation?

Name four methods to reduce the potential for audible noise in green mode supplies?

LED's (copy)

LED's Presented by Diana Izvorska

Why are LEDs more efficient than conventional light bulbs?

Why do LEDs offer a low cost of ownership?

Which way does current flow in a circuit?

What method would you use to dim a LED and why?

A customer wants to use LEDs in a parallel configuration, but he doesn't want to use balancing resistors. How might he achieve his aim?

What is the safety standard for lighting applications called?

What is the EMC standard called and what class harmonics the LED drivers should comply with?

External Energy Efficiency (copy)

External Energy Efficiency Presented by Les Chant

What are the two main reasons for wanting to control the Power taken by an external power supply?

Name the four main standards?

On what date did the 'Energy Independence and Security Act' come into force?

What are the four exceptions in the EISA legislation?

The Energy Star scheme has limits for No Load Power Consumption and Active Power Mode efficiency. What other criterion also needs to be taken into account?

How is the average efficiency calculated?

Which agency authored the test procedure document 'Test Method for Calculating the Energy Efficiency of Single Voltage AC-DC and AC-AC Power Supplies'?

What is the publication date of the test procedure document 'Test Method for Calculating the Energy Efficiency of Single Voltage AC-DC and AC-AC Power Supplies'?

Why can we not put an Energy Star logo, on our external power supplies?

A customer is looking for an external power supply. His requirements are, mains in, 12v @ 8.33A out, Energy Star level V compliance. What part would you offer?

Capacitor Lifetime (copy)

Capacitor Lifetime Presented by Stephen Dodson

What are the four points of the XP design rules?

What is the full name of the guy who came up with the basic rule?

What does his rule mean for the lifetime of capacitors?

What are the four things that generate heat in a capacitor?

Why do we estimate the lifetime once the power is installed into the end system?

Heatsinks (copy)

Heatsinks Presented by Les Chant

Explain why we need heatsinks?

Explain the ‘One dimensional thermal model’?

Using the “one dimensional model” you created, answer the following. Power = 50W maximum, junction temp. = 135degC maximum, thermal resistance = 0.75degC/W. What is the maximum. temperature of the device tab.

How much larger must the heatsink be made if we wish to reduce its thermal resistance by 50%?

When mounting a heatsink, how should it be done and what factors should be taken into account?

List 2 good conductors of heat and 2 poor conductors of heat?

Why is the environment important when selecting a heatsink?

I have a black anodised heatsink and a very nice polished heatsink. They are both exactly the same size. Which will radiate heat more effectively and why?

I have fitted the largest heatsink I can, and my calculations show that my device will still get too hot. What else can I do?