AC Motors 7.5KW driving with VFD methods using PIC18F46K22 and IR21362

[jean12]

Hello Dear,I am making a motor (AC MOTOR) driving with PIC18F46K22 I have well made the codes for my needs but the problem I now have is the interfacing the IGBT to the PIC,I do have ordinary drive IR21362 but I judged not enough to make on a given IGBT at a good time,so which component/circuit should I use so that before the current reaches the Gate of the IGBT be made good enough so the IGBT can operate effectively?

I have the IRG4PC50FD IGBT type and IR21362 IGBT drive;

Please help,

 

[FvM]

Re: Interfacing high current IGBT to PIC for three phase motor driving

IR21362 datasheet has curves for IRG4PC50FD, suggesting that driving this IGBT without additional current booster is at least possible. Although the recommended gat resistor of 5 ohm is used, you can expect that limited IR21362 output current will slow down switching of IRG4PC50FD.

Looking at IRG4PC50FD datasheet Fig. 9 switching losses versus gate resistance suggests however that reduced gate drive of IR21362 will increase switching losses only slightly, maximum 10 or 15 %. On the other hand it will make your inverter behave more peaceful.

 

[jean12]

Re: Interfacing high current IGBT to PIC for three phase motor driving

Thank you FvM for your response,it means if I interface the IR21362 to my PIC18F46K22,will this three phase induction motor of 7.5KW work perfectly?
What about protecting circuit of the IGBTs like snubber for example?

Please help!!

 

[jean12]

Hello,I would like to drive an AC three phase motor,I made a program with PIC18F46K22 and I am able to use a potentiometer and change its different parameters including frequency but now I have a problem of power to deliver to the ac motor as described it has 7.5KW and on my disposal I have the IGBTs

IIRG4PC50UD(600V,27A) and IRG4PC50FD(600V,39A) I would like to use those IRG4PC40UD could you please help me to determine if with those types that AC motor can operate its plate indicate 220/380V and 7.5KW.

Also ,I would like to ask if the three phase motor drive IR21362 and IR21365 one can replace another(if someone has worked with or understand its datasheet more than me )can help to explain to me.


Please help,regards,

 

[c_mitra]

I presume you are interested in speed control, and want lower/higher speed at full torque/ load.

I presume that the motor has a start-delta starter, it starts with 220VAC and perhaps takes around 30-40A current but after a few seconds switches on to 400VAC and takes around 15-20A current.

Your VFD must start with a low voltage and as the motor picks up speed, it should reach the full voltage and the target frequency. The full voltage depends on the target speed or frequency. Perhaps you cannot use a frequency less than 25-35Hz and cannot go above 100-200Hz. You need to figure out the voltages to be used for these extreme frequencies.

Next you will need to decide on the transistors and the drivers. It is good to be conservative and select a transistor that can handle twice the worst-case-current.

 

[FvM]

I presume that the motor has a start-delta starter, it starts with 220VAC and perhaps takes around 30-40A current but after a few seconds switches on to 400VAC and takes around 15-20A current.

A VFD operated motor doesn't use a star-delta starter. It speeds up with variable frequency and voltage. Therefore there will be usually no inrush current (at least not required by the motor). I agree however with the operation current estimation. 15 - 17 A phase current can be expected at rated motor load. Industry standard VFDs have a current boosting feature, delivering e.g. 150 or even 200 percent of rated current for a short time to be able to drive heavy loads requiring a breakaway torque.

The minimal requirement is that the peak phase current is lower than the rated IGBT current. Consider that the peak current flows quite a long time a low motor speed, you can't rely on IGBT peak ratings.

Practically, the IGBT selection will be ruled by the power dissipation (conduction + switching losses) in rated operation, heat sink thermal resistance and expected ambient temperature.

Another problem is about voltage rating. If I understand right, you are planning an inverter with 230/400 V three phase supply, resulting in 565 V DC bus voltage. It should never use 600 V rated IGBTs or MOSFETs, which are designed for 230V single phase supply.

 

[c_mitra]

A VFD operated motor doesn't use a star-delta starter.

Sorry if I was not clear; the boilerplate (post #4) suggested that the motor runs on 220/380V and this indicates that it is not originally designed to be run on a VFD but on a simple starter.

It is only one 3-PH supply but is often represented that way (220V/380V)

 

[c_mitra]

If I understand right, you are planning an inverter with 230/400 V three phase supply, resulting in 565 V DC bus voltage..

It is a simple three phase supply with neutral to phase voltage of 230V and phase to (another) phase voltage of 400 (slightly less actually). After rectification, you will get the same peak voltage- around 320V but with a higher ripple frequency and the output needs hardly any filtering. I do not see how you will get 565V DC from the three phase rectification.

 

[FvM]

After rectification, you will get the same peak voltage- around 320V but with a higher ripple frequency and the output needs hardly any filtering. I do not see how you will get 565V DC from the three phase rectification.

I wonder which rectifier topology you are discussing here.

A converter with 230 V single phase supply uses a bridge rectifier with 325 V bus voltage. (230 * √2).

An industry standard converter with 400 V 3 phase supply uses a three-phase bridge with 400 * √2 V bus voltage. The only way to get 325 V would be a neutral connected three phase half-wave rectifier, which won't be allowed due to DC input current.

 

[jean12]

I am using a three phase bridge rectifier for getting DC BUS voltage to supply my three phase IGBT bridge DC-AC Converter.
I connected a PIC to ULN2004 and then to IR21362 but I am not getting the output which means the IGBT are not really getting the controlling signal could you advise whether I have to boost the current or any other method I may Use?For the starting point of testing I am using a 300W three phase motor rated 220/400V.
In which case does an IR21362 be replaced by IR21365?
Please help!!

Regards,

 

[jean12]

Someone worked with IR21362 can help,I am measuring the signal on the IGBT gate making up my three phase bridge but I am getting a good signal only on one Gate,for the two remaining for the top side no goods signal ,I am using the 3 bootstrap capacitors of 22uF/50V.

Please help!!Best Regards,

 

[jean12]

Re: An843 three phase motor controller ps ground

Separating COM and VSS suggested in the IR21362 datasheet, implementing a current sense resistor. But to make the current sense resistor work, DC- must be connected on it's left side. AGND is apparently a singular net, looks like a typo. In case of doubt, refer to the IR21362 datasheet.

I am using the IR21362 for controlling a three phase bridge rectifier,if someone knows better about this can help to implement it,I did the connection as indicated in AN985 of infineon but the IGBT are not turning on,
could you advise what should be the role of ULN2004 before IR21362?If for example the ULN2004 can be of high importance because I am judging that the IR21362 is not receiving enough signal for turn-on operation because it is at 4.06V at IR21362 input which is the output of ULN2004 this also has its input on the output of PIC18F46K22.

Please advise what should be done for this operation.

Best Regards,

 

[FvM]

I would never use ULNxxx drivers as level converters for gate drivers and didn't yet saw anyone using it, because it's switching slow and will cause large delay skew. As open collector driver, it also need pull-up resistors.

Apart from these general reservations, it should at least work. I can just guess that there's a different problem in your circuit. Show a schematic.

According to datasheet, IR21362 logic inputs can be controlled by 5V CMOS logic (e.g. PIC processor) without level converters, in so far I don't understand the whole ULN thing.

I still wonder what's the designed DC bus voltage. Operating 600V rated IR21362 with 565 V DC sounds to me like courting disaster.

 

[jean12]

for DC bur refer to AN843 OF THE MICROCHIP,I try to remove the ULN and see if I could get the output,what should be the level of Pin 10(Enable) of IR21362?
Please help

 

[FvM]

what should be the level of Pin 10(Enable) of IR21362

Can use 5V logic, the same as HIN and LIN.

Driving EN from a processor is of limited use, I think. You can switch-off HIN and LIN as well to stop the output stage. If there's no independent hardware source of EN (e.g. voltage supervisor, watchdog or similar), you can also enable it permanently.

 

[jean12]

Yes,I would like to enable the driver permanently I place those 5V on it!

but still not reaction of the IR21362,when I take voltage measurement on the pin of the PIC I found around 3.8V(When selecting DC measurement with voltmeter),can this voltage drive the IR21362 so that we get the good signal output on the drive HO and LO?

Is there any techniques should I use for boosting that voltage from the PIC so that it reaches the level of 5V required by the IR21362?

Please help!!Thanks

 

[c_mitra]

PIC is going to drive the logic inputs of the IR21362 and that should not be a problem. You need to feed IR21362 with 5V input so that the levels will match...

 

[jean12]

I found that my quartz was not well connected with the PIC but using the potentiometer on RAO the multimeter shows (0.2V to 2.087V)will this voltage driver the IR21362?Or I need to step it up in order to obtain the +5V required by the IR21362?

Is it possible that we can get an output signal or a signal on the gate of any IGBT without applying the load on the bridge?

Please help!!All the best

 

[c_mitra]

You are supplying PIC with 5V, right? In that case, 2V output will be neither 0 nor 1. Please check. Does it light up a blue LED? Can you program the PIC?

 

[abc_de]

hello jean12
you can interface PIC with IR21362 driver by opto coupler like hcpl 2531 or direct non isolated connection and input of driver do not require high current and all. its pwm input is 3.3 V logic compatible.
if your using 3 phase supply then your driver is rated upto 600v. try to use another driver have rating is more then 600v. i will suggest Hcpl 316 i have also feature of Integrated fail-safe IGBT protection.
i do not know about your coding and all. have you test your pwm outputs microcontrollers pins dead time all.
for better discussion please share your schematic and how much work you have done