[horacioyalung]

I read somewhere that an industrial inverter can be use to power an ac motor for ev application. As we may all know, commercial high voltage inverters for EV are rather expensive. May I know the procedure on how to wire up the inverter to the asychronous motor? What would be an ideal converter to match this package assuming that I have the right inverter and motor. Thanks a bundle for your kind suggestion.

 

[remy_martian]

While it can be used, it's an ugly solution in terms of weight and reliability. Especially cooling. It's also not any cheaper unless you are parting out an industrial machine, though you could sell the components off and then buy automotive grade EV pieces.

This question seems to come up monthly here. Do a search on the forum.

It's not an "inverter", it's a "VFD" or "variable frequency drive". They will run off a DC supply. Connections are simple - three phase to the motor, two wires to the battery, not counting contactors, etc. Speed control is usually a voltage on a control interface.

 

[cricketo]

It's not an "inverter", it's a "VFD" or "variable frequency drive". They will run off a DC supply. Connections are simple - three phase to the motor, two wires to the battery, not counting contactors, etc. Speed control is usually a voltage on a control interface.

Serious question... how does a VFD convert single phase [email protected] into 3-phase 240VAC at arbitrary frequency ?

 

[remy_martian]

Rectify, filter to DC, synth a pseudo sine wave.

With 3 phase not much smoothing cap there which is why a 3 phase VFD will run on single phase but is power output derated.

It's what we call an inverter but with a rectifier & filtering (dc smoothing) front end.

There's also a line noise filter at the front end, also may be a PFC circuit given the caps in the filter.

 

[cricketo]

Rectify, filter to DC, synth a pseudo sine wave.

With 3 phase not much smoothing cap there which is why a 3 phase VFD will run on single phase but is power output derated.

It's what we call an inverter but with a rectifier & filtering (dc smoothing) front end.

There's also a line noise filter at the front end, also may be a PFC circuit given the caps in the filter.

so it quacks like a duck, but is a chicken ?

 

[brian_]

Serious question... how does a VFD convert single phase [email protected] into 3-phase 240VAC at arbitrary frequency ?

But is that really a serious question, though?

Rectify, filter to DC, synth a pseudo sine wave.

Yes.

And once there is DC, it doesn't matter whether the power came in a single-phase, three-phase, from a battery, or as a bolt of lighting caught by a key on a string by an old guy with long hair.
DC to three phases (or any number of phases) of AC is done by an inverter just like in every modern EV.


horacioyalung, what this means when using an industrial VFD is that you disconnect and ignore (and hopefully complete remove) the rectifier section in front, connect the input from the battery at the DC stage, and use only the inverter section. Of course there's a substantial controller component to control the inverter, and you need to keep that and figure out how to get it to take your control inputs. An industrial VFD normally gets a speed request, but in a car you want the accelerator pedal signal to be interpreted as a power or torque request... certainly not a set speed for each position of the pedal.

 

[cricketo]

But is that really a serious question, though?


Yes.
View attachment 125787

And once there is DC, it doesn't matter whether the power came in a single-phase, three-phase, from a battery, or as a bolt of lighting caught by a key on a string by an old guy with long hair.
DC to three phases (or any number of phases) of AC is done by an inverter just like in every modern EV.


horacioyalung, what this means when using an industrial VFD is that you disconnect and ignore (and hopefully complete remove) the rectifier section in front, connect the input from the battery at the DC stage, and use only the inverter section. Of course there's a substantial controller component to control the inverter, and you need to keep that and figure out how to get it to take your control inputs. An industrial VFD normally gets a speed request, but in a car you want the accelerator pedal signal to be interpreted as a power or torque request... certainly not a set speed for each position of the pedal.

It is a serious question because I thought they were inverters, but another person says they aren't. So I wanted to clarify in case I was missing something. Not everything is a trolling conspiracy.

 

[brian_]

It is a serious question because I thought they were inverters, but another person says they aren't. So I wanted to clarify in case I was missing something.

Okay, makes sense.

This is the part of the post which apparently raised the question:

It's what we call an inverter but with a rectifier & filtering (dc smoothing) front end.

Which means it is an inverter, plus a source of DC power, not something different from an inverter.

 

[remy_martian]

But is that really a serious question, though?


Yes.
View attachment 125787

And once there is DC, it doesn't matter whether the power came in a single-phase, three-phase, from a battery, or as a bolt of lighting caught by a key on a string by an old guy with long hair.
DC to three phases (or any number of phases) of AC is done by an inverter just like in every modern EV.


horacioyalung, what this means when using an industrial VFD is that you disconnect and ignore (and hopefully complete remove) the rectifier section in front, connect the input from the battery at the DC stage, and use only the inverter section.

You don't HAVE to hack into the DC bus if you want to be able to use/resell the VFD later. It's just more efficient to connect directly to internal the DC bus, but not recommended for people who ask how. Just need to hope the diodes have enough thermal margin to do this as diodes run at ~50% duty cycle.

Just connect one of the three input phases of the VFD to your positive battery supply and one of any of the other input phases to negative. The third, "dangling" input needs to be safe...do not leave a wire hanging off that input that's disconnected - just leave it disconnected from what's usually a wire terminal block.

You'll lose a bit of power in the diodes, but better than dicking with (an engineering term) taking off the cover and with the high voltage innards of the VFD.

Some VFD's may alarm an input phase fault...just ignore it if it can.

 

[remy_martian]

One other important consideration. A VFD is not designed to run in harsh automotive environments. That goes for temperature, moisture, dust, etc.

 

[brian_]

You don't HAVE to hack into the DC bus if you want to be able to use/resell the VFD later. It's just more efficient to connect directly to internal the DC bus, but not recommended for people who ask how. Just need to hope the diodes have enough thermal margin to do this as diodes run at ~50% duty cycle.

Just connect one of the three input phases of the VFD to your positive battery supply and one of any of the other input phases to negative. The third, "dangling" input needs to be safe...do not leave a wire hanging off that input that's disconnected - just leave it disconnected from what's usually a wire terminal block.

You'll lose a bit of power in the diodes, but better than dicking with (an engineering term) taking off the cover and with the high voltage innards of the VFD.

Fair enough... but I hope this is a pickup truck, to carry all the of extra hardware in the cargo box.

I think anyone who is not up to touching the internals of the VFD is going to have trouble integrating the components of the system, including making the drive work with a motor which is substantially different from what the drive is intended for.

 

[remy_martian]

There are a lot of industrial electricians out there...

...some collect free stuff off jobsites

 

[remy_martian]

so it quacks like a duck, but is a chicken ?

More of the egg before chicken kind of a question 😂