MME 3374a Electrical Foundations for Mechanical Engineers - Power Electronic Devices

These flashcards cover key concepts from the Power Electronic Devices module, including diodes, MOSFETs, thermal management, and circuit behaviors.

In the context of power electronic devices, the process of converting electrical energy to other forms of energy on a larger scale involves switching __ loads.

inductive

A basic rule essential to understanding inductive loads is __'s law, which describes the behavior of inductors when the current through them changes.

Lenz

When the switch opens, the voltage across the inductor can reach up to __ volts for a 100 μH inductor with a 10 A current.

1000

The voltage across a switch or relay contact during disconnection of an inductive load may cause __ which leads to wear of the contacts.

arcing

To handle turn-off energy in inductors, a __ diode is typically used.

Freewheeling

Without a freewheeling diode, an inductor's current falls to zero in a __ time, leading to a large voltage across the switch.

very short

The clamping voltage in the case of a freewheeling diode is the sum of the forward voltage drop and the supply voltage (Vsw = __ + Vs).

VD

Diodes allow current to flow in one direction and block it in the __ direction, much like a check valve in fluid power.

reverse

A diode that conducts in the reverse direction when reverse voltage exceeds a certain limit is said to reach its __ voltage.

breakdown

A diode will experience a __ voltage drop when it is forward biased.

forward

The maximum reverse voltage a diode can withstand without conducting is referred to as the __ Inverse Voltage (PIV).

Peak

Thermal management for diodes requires consideration of ambient __ and maximum forward current.

temperature

If the junction temperature (Tj) exceeds the maximum specified value, the diode may __.

fail

In steady-state conditions, if PD is known, we can calculate Tj using the formula Tj = PD * RΘja + Ta, where Ta is the ambient __.

temperature

Zener diodes are constructed to have a fixed __ voltage when reverse biased.

breakdown

A __ diode can act as a voltage reference in circuits.

Zener

The power MOSFET has played a significant role in enabling technologies such as power inverters and solid-state motor __.

drives

The two families of power MOSFETs based on semiconductor construction are __ and P channel.

N channel

The __ of a power MOSFET is determined by its gate voltage and results in current flow from the drain to the source.

operation

The turn-on and turn-off characteristics of a MOSFET can result in __ losses due to finite resistance in the conducting state.

power

The turn-on loss for a MOSFET can be calculated using the formula PD On = ½ * fSW * VS * IO * tswon, where fSW is the __ frequency.

switching

Power dissipated by a half-wave rectifier diode can be approximated using the formula PD = Vd * I rms, where Vd is the forward __ drop.

voltage

When using a MOSFET in a PWM circuit, the average current through the inductor equals approximately __ A during conduction.

5

A major advantage of using PWM is its efficiency compared to using a MOSFET as a __ resistor.

variable

To mitigate thermal cycling that leads to device failure, a semiconductor may be mounted to a __ using a thermally conductive material.

heatsink

The thermal resistance between the junction and ambient is critical for __ management in electronic components.

thermal

Ripple current and temperature significantly affect the __ life of electrolytic capacitors.

usable

The equivalent series resistance (ESR) of an electrolytic capacitor increases as it approaches its __ life.

end-of-life

Electrolytic capacitors are used to stabilize voltage supply in power electronic circuits by providing __ to maintain voltage levels.

current

The breakdown voltage of a Zener diode can be several __ volts and is used for voltage regulation.

hundred

In PWM control, if a MOSFET's on-resistance is too high, it can lead to excessive __ losses.

conduction

When a diode reaches reverse breakdown, it can conduct in the reverse direction, similar to how a mechanical _ would fail under pressure.

check valve

An idealized pulse-width modulation waveform gives a duty cycle equal to the ratio of on time to __ time.

total

For a half-wave rectified sine wave at 60Hz, the RMS current is calculated as the peak voltage over __ resistance.

load

A power MOSFET typically has ratings that include breakdown voltage, current ratings, and __ resistance when fully turned on.

Drain-Source

The __ frequency of PWM controls affects the power dissipation in MOSFETs used for switching.

switching

Using resistive control leads to high losses compared to PWM because it does not turn the MOSFET fully __.

on

Capacitance in the switching process of a MOSFET influences the speed at which it can turn on and off due to inherent __.

capacitances

The average power across the inductor in a PWM circuit can be expressed as the product of the __ Cycle and the Supply Voltage.

Duty

The short circuit failure of MOSFETs often leads to a hard short circuit between Drain and __.

Source

In the thermal model, the RΘja is defined as the thermal resistance from the junction to the __ of the device.

ambient

When a MOSFET is switched off, it requires careful handling of the __ energy in the inductive loads.

turn-off

The reliability of an electronic device is expected to halve for every 10 degree Celsius rise in __, as described by Arrhenius’ Rule.

temperature