Switched-mode power supplies

The experiments are carried out on training panels in panel frames.

Objectives

• Protective measures and electrical safety
• Circuit assembly and connections according to circuit diagrams
• Use of Power Analyser CASSY Plus

Power electronics enables the construction of power supplies that are characterised by high efficiency and small size. This is achieved with switching components and at the highest possible switching frequencies. The following experiments on primary switched-mode power supplies can be set up and examined with regard to their properties:

Buck converter

• With different loads,
• Control of the voltage and current average by means of pulse width modulation,
• Function of a free-wheeling diode with ohmic inductive load,
• Function of a smoothing capacitor with ohmic inductive load,
• Efficiency of the buck converter

Inverting boost and buck converter

• With different loads,
• Control of the voltage and current average using pulse width modulation,
• Function of choke with gap current

Highlights:

• To protect the semiconductor components, all experiments are only tested with a low voltage.
• The measurements are carried out with the Power Analyser Plus.
• All measurement channels are potential-free and can therefore be used freely.
• All measurements can be carried out with or without a computer.

All functions of the Power Analyser CASSY can be operated quickly and directly via the display, the rotary wheel and the buttons on the unit. All settings and measurement results can be saved on the unit and quickly called up again later or simply downloaded.

In addition, the Power Analyser CASSY is fully controllable in real time via RJ45 Ethernet, W-LAN and USB-C interfaces.

These interfaces can be used by the following software:

• CASSY Lab 2 for drives and energy systems,
• MATLAB® and LabVIEW ™
• Lab Docs Editor Advanced

The following integrated servers are available in the Power Analyser CASSY for the local media connection of at least four end devices simultaneously.

For more details, see product data 727110 or 727111 Power Analyser CASSY.

The individual equipment is equally suitable for student experiments in the laboratory with low voltage (230 / 400 V three-phase current) and - with a mobile trainer - for teacher demonstration in the classroom. The experiments are carried out according to the manual.

The target group is made up of commercial apprentices and students of electrical machine construction. The course offers experiments at an intermediate level and also allows for the necessary insight into machine behaviour for scientific interpretation at undergraduate level. The media connection makes the experiments suitable for demonstration in the classroom or a lecture hall.

In the following configurations there are further extended experiments of the power electronics:

• E2.4.3.1 Switchable valves and DC controllers
• E2.4.3.3 Inverters
• E2.5.2.2 Four-quadrant drive of a DC machine with an IGBT H-bridge circuit

Topics

Buck converter

• Control of average values for voltage and current using PWM
• How voltage and current change over time with a resistive load
• How voltage and current change over time with a resistive-inductive load
• Resistive-inductive load with freewheeling diode and smoothing capacitor
• Buck converter with V_I = 110 V, losses, efficiency

Boost/buck converters

• Control of average values for voltage and current using PWM
• Measurement of voltage and current over time when V_I = 15 V
• Measurement of voltage and current over time when V_I = 110 V
• Measurement with intermittent choke current

Boost/buck converters with power factor correction

• Effect of hysteresis