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Both IGBT and MOSFET are the best as per application.
I am designing high efficiency grid inverter for PV with dual buck topology for 300 watt system. During my simulation I saw that the body diode of two Mosfet switches getting turning on and this switches running on grid frequency (50 Hz). And other two Mosfet's body diode of the inverter are silent during operations. And that is running at PWM frequency. One option I feel that I could replace igbt that will switch on grid frequency or else in the mosfet switch I could put an inductor to avoid the diode getting turning on. but if choose igbt i will get high on state losses compare to mosfet due to small current I= 1.30 rms and mosfet fits for that.
I am designing high efficiency grid inverter for PV with dual buck topology for 300 watt system. During my simulation I saw that the body diode of two Mosfet switches getting turning on and this switches running on grid frequency (50 Hz). And other two Mosfet's body diode of the inverter are silent during operations. And that is running at PWM frequency. One option I feel that I could replace igbt that will switch on grid frequency or else in the mosfet switch I could put an inductor to avoid the diode getting turning on. but if choose igbt i will get high on state losses compare to mosfet due to small current I= 1.30 rms and mosfet fits for that.
Tags: inverter, Grid inverter
IGBT die are most commonly designed without an integral (monolithic) anti-parallel diode because they can be better optimized for particular forward parameters that way. Separate antiparallel diode die can then co-packaged for topologies that require it. This makes it easier to fully optimize the forward and reverse characteristics of the compound device. The disadvantage is that the co-packaging takes-up some extra room, and the wirebonds add a small amount of parasitic inductance. But co-packaged IGBTs like this are still the dominant devices used in motor drives and other inverter applications. One additional benefit of IGBTs is that they can be designed to survive a direct short-circuit across the bus, for several microseconds (Short Circuit SOA capability), versus Superjunction FETs do not have this capability.
Superjunction FETs on the other hand have a parasitic body diode (like all vertical FETs), whether you like it or not. The advantage of the superjunction process is that it can produce a very low ON resistance at high voltage using less silicon area than other methods. However, the big disadvantage of superjunction is that the body diode dynamic performance is poor. Even with special doping and irradiation - it might get a little better, but it is in a completely different league compared to an optimized fast diode or SiC Schottky.
Superjunction FETs on the other hand have a parasitic body diode (like all vertical FETs), whether you like it or not. The advantage of the superjunction process is that it can produce a very low ON resistance at high voltage using less silicon area than other methods. However, the big disadvantage of superjunction is that the body diode dynamic performance is poor. Even with special doping and irradiation - it might get a little better, but it is in a completely different league compared to an optimized fast diode or SiC Schottky.
Tags: Definition, inverter
We can six stepped for higher power motor like >50KW, where inverter switches doesn't respond too fast for the digitally modulated PWM (Space vector or Sine wave PWM) using a DSP or a controller or even a FPGA.
In high power applications, six stepped modulation has higher advantages to motor like:
1, Higher average starting torque output (irrespective of construction of the motor - Axial magnets or radial magnetic field)
2, Can be used easily for high speed motors where any modulation technique cannot be used.
And for de-merits, I think everyone knows the de-merits since he final output is not sinusoidal and it is just near sinusoidal.
Just be careful about the harmonic current at the output of inverter that is too dangerous as I2R losses increase as a function of harmonic current.
In high power applications, six stepped modulation has higher advantages to motor like:
1, Higher average starting torque output (irrespective of construction of the motor - Axial magnets or radial magnetic field)
2, Can be used easily for high speed motors where any modulation technique cannot be used.
And for de-merits, I think everyone knows the de-merits since he final output is not sinusoidal and it is just near sinusoidal.
Just be careful about the harmonic current at the output of inverter that is too dangerous as I2R losses increase as a function of harmonic current.
Tags: inverter, Sine wave inverter
Power factor is a measurement of reactive power. Reactive power is the VA used to establish the magnetic field in a motor. For permanent magnet motor, most time you see power factor being unity, which means all VAs are used to generate torque (minus the loss, of course). Under the condition of field weakening operation though, you will see the PM motor gets less than unity power factor because some VAs are used to counter the perm magnet field. In induction motor, the power factor indicates the portion of VAs used to generate the field comparing to the VAs that generate torque (and loss), which is related to the v/hz in scalar controller or Id in vector control. So under light load condition, you can improve the power factor of an induction motor by lowering the field a bit.
The motor power factor does not make a big difference other than giving an idea of loading. In regards to the inverter fixing power factor everyone is mostly correct. An inverter will always show a DPF (Displacement Power Factor) near unity. DPF is what a utility company traditionally monitors and is the measure of lag looking at current and voltage of power at 60hz or fundamental only. The true power factor on an frequency inverter will change with loading etc and includes current and voltage inclusive of harmonics.
The motor power factor does not make a big difference other than giving an idea of loading. In regards to the inverter fixing power factor everyone is mostly correct. An inverter will always show a DPF (Displacement Power Factor) near unity. DPF is what a utility company traditionally monitors and is the measure of lag looking at current and voltage of power at 60hz or fundamental only. The true power factor on an frequency inverter will change with loading etc and includes current and voltage inclusive of harmonics.
Tags: Definition, Energy saving
New regulations are demanding higher efficiency for applications such as pump and fan drives. To achieve this, PM motors have been used for a few years now. The downside of those being the expensive magnets of course. The efficiency of the synchronous reluctance motor is not as good as the PM, but although it isn't more expensive than the induction motor, it still has higher efficiency.
Our customers are very interested in this technology, but so far there aren't that many manufactures producing the motors. I think this could change soon though.
As you have mentioned, the big advantage of the synchronous reluctance over the switched reluctance is, that it can be driven by a standard 3 phase inverter. To be honest, I am not really sure why people are using switched reluctance rather than synchronous reluctance at all.
Our customers are very interested in this technology, but so far there aren't that many manufactures producing the motors. I think this could change soon though.
As you have mentioned, the big advantage of the synchronous reluctance over the switched reluctance is, that it can be driven by a standard 3 phase inverter. To be honest, I am not really sure why people are using switched reluctance rather than synchronous reluctance at all.
Tags: Motors
STO (Safe Torque OFF) function refers to the functional safety of the
machine, not to the electrical safety. STO guarantees that there will be
no torque on the motor, so the machine is not able to move. Therefore
the machine can not make any damage to persons or property. If you need
to make any maintenance to the motor/machine you will have to remove the
power supply to the machine (to the inverter) in order to ensure the
electrical safety.
The big advantage of STO function is that it can replace the contactors at the output of the inverter, thus giving the following advantages:
The big advantage of STO function is that it can replace the contactors at the output of the inverter, thus giving the following advantages:
- No wear of the contactors, with virtual unlimited number of stop/start operations
- Cheaper and easier installation, because you are saving the output contactors
- Better EMC behavior (there is a perfect continuity of the motor cable shield)
- No acoustic noise due to the contactors (in some applications like elevators acoustic noise is relevant)
Tags: Electrical safety
Basically higher switching frequency allows smaller magnetic cores to be used with fewer turns. But often you are then constrained by the available winding space for your copper wire. While a toroidal core is the ideal shape for magnetic efficiency, giving the best ratio of Ae/le, E & I cores are far more practical and cheaper to wind. In addition with off-line swichers for example, you have to compromise on best winding arrangements to achieve lowest leakage inductance for safety margin in creepage and clearances. Primary and secondaries are then bobbin wound with deep plastic cheeks between primary and secondaries to provide the necessary insulation barriers to meet a 4kV safety flash test.
Switching loss will go up with frequency as you would expect, requiring faster semiconductors and gate drive circuitry. Then you would probably have to slow down your edges to reduce EMC, trading one against the other.
Hysteresis and eddy current loss in the ferrite will increase with frequency and core flux density as will the ac resistance or skin effect of your wire. This is offset by less turns and less ferrite and working at lower flux density and the use of Litz wire, (if you are very desperate for efficiency).
Switching loss will go up with frequency as you would expect, requiring faster semiconductors and gate drive circuitry. Then you would probably have to slow down your edges to reduce EMC, trading one against the other.
Hysteresis and eddy current loss in the ferrite will increase with frequency and core flux density as will the ac resistance or skin effect of your wire. This is offset by less turns and less ferrite and working at lower flux density and the use of Litz wire, (if you are very desperate for efficiency).
Tags: Power supply
Energy saving using inverter is always vary application to application. Following points you need to consider before using inverters for energy saving.
Energy savings as it relates to frequency inverters as above explained. My technology uses negative amp draw to develop the torque in our motors, the traditional amp draw is blocked bi-directionally by our power electronics. Hence, our electric power consumption neutralization platform is an electric power production and a power performance platform as opposed to an inverter energy savings and performance sacrificing platform.
- How much process flow and pressure requirement through AC motors
- Existing control methodology like control valve in pumps, Damper or guide vane for Fans & Blowers etc. and position of the valve or dampers
- If you have process flow and pressure data and pump or fan design data, you can calculate energy saving using affinity law
- Loading and Unloading cycle for compressor application. If the unloading time is higher for compressor application, you will get better energy saving
- Using affinity law, you can calculate the energy saving with consideration of inverter losses. With this you can calculate the Pay back of inverters.
Energy savings as it relates to frequency inverters as above explained. My technology uses negative amp draw to develop the torque in our motors, the traditional amp draw is blocked bi-directionally by our power electronics. Hence, our electric power consumption neutralization platform is an electric power production and a power performance platform as opposed to an inverter energy savings and performance sacrificing platform.
Tags: inverter, Energy saving
Computation delay in digital systems translates to additional phase loss. This phase loss at any frequency f is given by 360*f/fs, where fs is the digital loop sampling frequency. So if we can maintain high fs compared to the bandwidth fc then the phase margin reduction caused by the delay at the crossover frequency (fc) is minimized. This also means that for high BW digital system the delay must be minimized as Ron entioned.
Digital gives some advantage while closing some loops. For ex, UPS output voltage loop the integrator in the compensator can be changed to provide high gain at the UPS output frequency and not necessarily at DC. For high Q buck, digital allows for better loop response by use of complex zero compensation. This can also be used in PFC current loop or Solar inverter current loop with LCL type output filter.
Digital gives some advantage while closing some loops. For ex, UPS output voltage loop the integrator in the compensator can be changed to provide high gain at the UPS output frequency and not necessarily at DC. For high Q buck, digital allows for better loop response by use of complex zero compensation. This can also be used in PFC current loop or Solar inverter current loop with LCL type output filter.
Tags: inverter
This is a recurring question for me in my Soar Academy classes and is
gaining traction. I want to add that the SMA Sunny Island can be used
with any solar/wind inverter regardless of make. SMA is coming out with
our own micro inverter after SPI and it will be able to be used with the
SI45/50/6048U inverters, although initially, it will not respond to the
Sunny Island frequency shifts.
That being said, the only issue with a non-SMA inverter will occur when the following three conditions exists:
1. The grid is out (or in a standalone system)
2. The batteries are fully topped off
3. There is no demand on the protected loads panel
If these three conditions are met, the Sunny Island will increase the micro grid frequency to throttle the RE inverters down to 0W to prevent battery overcharge. With a non-SMA inverter, it will not respond to these frequency shifts and as soon as the frequency hits the UL1741 limit of 60.5Hz it will immediately disconnect from the grid. Worst case, you will have to wait 5 minutes when the Island recognizes a demand and the isolation relays in the inverters will be overexercised. Not a big deal really.
That being said, the only issue with a non-SMA inverter will occur when the following three conditions exists:
1. The grid is out (or in a standalone system)
2. The batteries are fully topped off
3. There is no demand on the protected loads panel
If these three conditions are met, the Sunny Island will increase the micro grid frequency to throttle the RE inverters down to 0W to prevent battery overcharge. With a non-SMA inverter, it will not respond to these frequency shifts and as soon as the frequency hits the UL1741 limit of 60.5Hz it will immediately disconnect from the grid. Worst case, you will have to wait 5 minutes when the Island recognizes a demand and the isolation relays in the inverters will be overexercised. Not a big deal really.
Tags: inverter, Micro inverter
Electrical environment
A. Prevent overvoltage in input terminal
The main circuit of the inverter is consisted of power electronic parts, these devices are very sensitive on the voltage, the over voltage on input terminal will cause permanent damage of the main components. For example, some factories have their own electricity generator, power grid fluctuation is relative high, so they should have precautions on the input voltage of the frequency inverter.
B. Prevent electromagnetic interference
The inverter main electrical components are power module and control system hardware and software circuit, If these components and software programs are impacted by a certain electromagnetic interference, it will cause hardware circuit malfunction, software program failed and then cause accident. So, in order to avoid electromagnetic interference, the variable frequency inverter needs to prevent electromagnetic interference according the electrical environment. For example: the input power cord, output motor lines, control lines shall be kept away from each other; The devices and signal lines which are easily affected, should be installed as far as possible from the frequency inverter; The critical signal lines should be shielded cable, it is recommended to use shield cable with 360° grounded.
A. Prevent overvoltage in input terminal
The main circuit of the inverter is consisted of power electronic parts, these devices are very sensitive on the voltage, the over voltage on input terminal will cause permanent damage of the main components. For example, some factories have their own electricity generator, power grid fluctuation is relative high, so they should have precautions on the input voltage of the frequency inverter.
B. Prevent electromagnetic interference
The inverter main electrical components are power module and control system hardware and software circuit, If these components and software programs are impacted by a certain electromagnetic interference, it will cause hardware circuit malfunction, software program failed and then cause accident. So, in order to avoid electromagnetic interference, the variable frequency inverter needs to prevent electromagnetic interference according the electrical environment. For example: the input power cord, output motor lines, control lines shall be kept away from each other; The devices and signal lines which are easily affected, should be installed as far as possible from the frequency inverter; The critical signal lines should be shielded cable, it is recommended to use shield cable with 360° grounded.
There are local start/stop and remote start/stop, function set,
parameter set, fault inquiry, operation record on WINDOWS interface.
Set inverter parameters by colorful LED touch-screen. Output operation data table can be printed out. HMI can display voltage/ current waveform, frequency, speed and motor status at any time.
Good ability in detecting and indicating: operation status of every part of inverter can be detected. Integrated fault monitor circuit, accurate fault orientation, fault position and type showing in HMI make fault points clear at a glance. Easy replacement of broken cell reduces MTTR and can be operated by general personnel.
Set inverter parameters by colorful LED touch-screen. Output operation data table can be printed out. HMI can display voltage/ current waveform, frequency, speed and motor status at any time.
Good ability in detecting and indicating: operation status of every part of inverter can be detected. Integrated fault monitor circuit, accurate fault orientation, fault position and type showing in HMI make fault points clear at a glance. Easy replacement of broken cell reduces MTTR and can be operated by general personnel.