Thoughts on this VFD

[Ubique]

Sorry, the MPPT range (i.e. DC input range from the PV cells) is 100 to 800V, {most have a Vmax of 1kV} which runs through a DC-DC converter to lift or drop the voltage depending on the variable output from the PV's You may well be right about a small power transformer, beyond the input/output specs and usage cases, I've yet to look at the actual internal construction of them.

 

[Hood]

It is the two speed motor

Would just choose one of the motor speeds and vary frequency maybe?

You would have to but as said I am not sure if you can wire them for 240v as I think they connect delta for one speed and Y for the other. Then again I don't know much about these things so...

 

[Lewis_RX8]

You would have to but as said I am not sure if you can wire them for 240v as I think they connect delta for one speed and Y for the other. Then again I don't know much about these things so...

Will wait and see what the connections are like when I open the box and what the data plate says

Hoping to see something like this from a motor at my work so we can get it in detla

 

[Munkul]

That was the plan wire it up to Delta but I've seen some one has said about some older and bigger motors not being suited to that but not sure yet.

Ronan runs his off a VFD which is similar so think it should be alright

Technically only newer motors are actually VFD rated. Most older motors aren't. They'll still run on 240v delta and on VFDs as long as you don't push the current too hard. You can always limit the current in the VFD setup to give a little bit extra margin.

 

[Munkul]

Ah - dual wound motor. different kettle of fish. You'll have to change the motor I think.

 

[Hood]

You will see six wires if it is a two speed but that will not mean it can run 240v.
Just looked in a manual for a Clausing (same as Triumph roundhead) and this is what it shows.
Connect 4, 5 and 6 for High, so Y?
and 1, 2 and 3 for low so Delta.?

 

[carbon]

Hoping to see something like this from a motor at my work so we can get it in detla

If im not mistaken that motor is already wired in delta

 

[Lewis_RX8]

If im not mistaken that motor is already wired in delta

yea , Meant more the way the box is laid out having access to all the connections but not sure how it will work with the dual speed.

You will see six wires if it is a two speed but that will not mean it can run 240v.
Just looked in a manual for a Clausing (same as Triumph roundhead) and this is what it shows.
Connect 4, 5 and 6 for High, so Y?
and 1, 2 and 3 for low so Delta.?

View attachment 316362

Should have posted this earlier my bad but this is from the triumph manual for the dual speed

That clausing manual is very helpful showing it actually wired up in star and delta assuming its same as UK machine motor. Odd it isn't in the UK manual

Thanks for finding that.

 

[Agroshield]

The most common way to wire two speed motors is what is called a Dahlender motor connection. Google it and read about it. They will not run on low voltage 3-phase. In effect, they are [high voltage] delta for one of the speeds and what you could call [high voltage] 'double delta' for the other speed.

Edit: added [high voltage] as original may have been misleading

 

[Fastdruid]

Ah - dual wound motor. different kettle of fish. You'll have to change the motor I think.

You can use a dual wound, it's just not ideal and probably have to dig about in it.

 

[Ubique]

Steady on, most string inverters will operate up to 600v DC. Some to 1000V. You may mean 1200V DC, not 120V.

Shading causes all the panels in the string to reduce output to the level of the affected panel(s). Anything over 360V DC is already above the grid peak voltage of 358V AC (to produce an RMS AC output of 254V (the highest value allowed for your nominal 230V grid supply).

The inverters I am currently installing on my house are individual to each panel, so only 60V DC maximum (that is OC voltage, not the maximum power point voltage). Far safer for the fire brigade in the evant of an emergency (as they cannot go messing around on a roof with high DC voltages which are likely to zap them).

The oldest grid-tie inverters I have require from about 70 -150 volts. 70 is operational at the maximum power point and the 150 is the max open circuit voltage permissible. Those inverters are over ten years ancient.

They were not installing simple string inverters. See my later post for MPPT voltages in general terms.

 

[m_c]

Given it's a dual speed motor, I'd just buy a 'Boost' VFD, and wire it directly to the motor, probably picking high speed.
Two main Chinese suppliers that I know off are CNCWeiken ( 220V to 380V VFD - Shop Cheap 220V to 380V VFD from China 220V to 380V VFD Suppliers at CNWeiKen Official Store on Aliexpress.com ) ,and Ecogoo ( 0.75kw---11kw - Shop Cheap 0.75kw---11kw from China 0.75kw---11kw Suppliers at ECOGOO Electric Store on Aliexpress.com )

Only concern is, as has already been mentioned, is older motors won't use inverter rated insulation. The output from a VFD often contains transients, that can cause older insulation to break down, eventually leading to failure and shorts within the motor. However plenty people do run old motors on VFDs without issue, but if you want to eliminate the possible risk, you can add in a sine wave filter (essentially three chokes to smooth the VFD output, along with voltage suppressors on the output side to kill any high voltage transients).

For the suds pump, either swap the pump, or add another VFD.

I'm personally running my workshop from a CNC Weiken Boost VFD, but for hard starting motors, you need a good margin to handle the start-up surge, which for a lathe which is likely to have a lot of weight to get spinning, you're probably looking at a 3x safety margin. Having the lathe VFD controlled, removes that requirement from your supply.



As for those arguing over boosting voltage. You can double voltage using basic electronics. No transformers needed. Need more than double the voltage, just double it again. If don't need quite double voltage, regulate the doubling process, so it never quite doubles voltage.

 

[daleyd]

Given it's a dual speed motor, I'd just buy a 'Boost' VFD, and wire it directly to the motor, probably picking high speed.
Two main Chinese suppliers that I know off are CNCWeiken ( 220V to 380V VFD - Shop Cheap 220V to 380V VFD from China 220V to 380V VFD Suppliers at CNWeiKen Official Store on Aliexpress.com ) ,and Ecogoo ( 0.75kw---11kw - Shop Cheap 0.75kw---11kw from China 0.75kw---11kw Suppliers at ECOGOO Electric Store on Aliexpress.com )

Only concern is, as has already been mentioned, is older motors won't use inverter rated insulation. The output from a VFD often contains transients, that can cause older insulation to break down, eventually leading to failure and shorts within the motor. However plenty people do run old motors on VFDs without issue, but if you want to eliminate the possible risk, you can add in a sine wave filter (essentially three chokes to smooth the VFD output, along with voltage suppressors on the output side to kill any high voltage transients).

For the suds pump, either swap the pump, or add another VFD.

I'm personally running my workshop from a CNC Weiken Boost VFD, but for hard starting motors, you need a good margin to handle the start-up surge, which for a lathe which is likely to have a lot of weight to get spinning, you're probably looking at a 3x safety margin. Having the lathe VFD controlled, removes that requirement from your supply.



As for those arguing over boosting voltage. You can double voltage using basic electronics. No transformers needed. Need more than double the voltage, just double it again. If don't need quite double voltage, regulate the doubling process, so it never quite doubles voltage.

Of course you can boost voltage using electronics, no ones saying you can’t - what’s uncommon is using that technique in power stages of inverters (for example) where you need to boost voltage along with (relatively) high current. Using voltage boosting circuits is done routinely for smaller low powered circuits requiring high voltage/low current.

 

[m_c]

Of course you can boost voltage using electronics, no ones saying you can’t - what’s uncommon is using that technique in power stages of inverters (for example) where you need to boost voltage along with (relatively) high current. Using voltage boosting circuits is done routinely for smaller low powered circuits requiring high voltage/low current.

It's what's used in boost VFDs. They don't contain any transformers big enough to handle multiple KWs. Voltage doubling is maybe crude, but it does the job, even at high voltages and currents.

 

[Agroshield]

...for hard starting motors, you need a good margin to handle the start-up surge, which for a lathe which is likely to have a lot of weight to get spinning...

Could you flesh out that comment a little please. I was under the impression that the soft start functionality of VFD's (i.e. ramping the frequency up from zero to 50Hz in a user-defined leisurely time) eliminated most of the start up problems (i.e. trying to go from off to 50Hz in an instant). The two sentences in the paragraph from which the quote is taken seem to contradict each other.

Is it the case with the boost ones that you lose the ramping ability completely or is it just easier to wire it up without that ability?

Thanks.

 

[daleyd]

It's what's used in boost VFDs. They don't contain any transformers big enough to handle multiple KWs. Voltage doubling is maybe crude, but it does the job, even at high voltages and currents.

The only ones I know use a step up transformer on the input side, or at least that’s how they have been described by people that have them - if you say different then I’ll have to take your word.

 

[Lewis_RX8]

Given it's a dual speed motor, I'd just buy a 'Boost' VFD, and wire it directly to the motor, probably picking high speed.
Two main Chinese suppliers that I know off are CNCWeiken ( 220V to 380V VFD - Shop Cheap 220V to 380V VFD from China 220V to 380V VFD Suppliers at CNWeiKen Official Store on Aliexpress.com ) ,and Ecogoo ( 0.75kw---11kw - Shop Cheap 0.75kw---11kw from China 0.75kw---11kw Suppliers at ECOGOO Electric Store on Aliexpress.com )

Only concern is, as has already been mentioned, is older motors won't use inverter rated insulation. The output from a VFD often contains transients, that can cause older insulation to break down, eventually leading to failure and shorts within the motor. However plenty people do run old motors on VFDs without issue, but if you want to eliminate the possible risk, you can add in a sine wave filter (essentially three chokes to smooth the VFD output, along with voltage suppressors on the output side to kill any high voltage transients).

For the suds pump, either swap the pump, or add another VFD.

I'm personally running my workshop from a CNC Weiken Boost VFD, but for hard starting motors, you need a good margin to handle the start-up surge, which for a lathe which is likely to have a lot of weight to get spinning, you're probably looking at a 3x safety margin. Having the lathe VFD controlled, removes that requirement from your supply.



As for those arguing over boosting voltage. You can double voltage using basic electronics. No transformers needed. Need more than double the voltage, just double it again. If don't need quite double voltage, regulate the doubling process, so it never quite doubles voltage.

This seems promising thanks for the link and good to hear your workshop runs on it , also only £170 or so for a boost converter for 7.5kw which is about what the UK non boost one costs so a good price. If the motor dosent run on 220v then I would probably use these to run the lathe

Will look into the old motor Vfds and the electronics to get rid of the transients sounds worth doing if it could burn the motor out.

Also interested in your workshop setup , how did you wire it to run the whole workshop rather than just a vfd per machine and interested like the others why you have the 3x saftey margin when they can soft start.

Thanks for the link to the boost converters again glad the motor can be run with minimal messing about from one of them

 

[Ubique]

Could you flesh out that comment a little please. I was under the impression that the soft start functionality of VFD's (i.e. ramping the frequency up from zero to 50Hz in a user-defined leisurely time) eliminated most of the start up problems (i.e. trying to go from off to 50Hz in an instant). The two sentences in the paragraph from which the quote is taken seem to contradict each other.

Is it the case with the boost ones that you lose the ramping ability completely or is it just easier to wire it up without that ability?

Thanks.

Think of it like pulling away from a standing start in your car, whether you go racing off from the lights or just take a leisurely pace, you still need the same amount of torque to get the wheels moving. More torque is required if you have a boot full of cast iron to overcome the rolling resistance (friction).

 

[daleyd]

Think of it like pulling away from a standing start in your car, whether you go racing off from the lights or just take a leisurely pace, you still need the same amount of torque to get the wheels moving. More torque is required if you have a boot full of cast iron to overcome the rolling resistance (friction).

My guess is it’s because m_c uses his vfd as a static converter rather than using it as a vfd, if you do it this way and utilise the existing switchgear you need a significant margin to allow for start up currents, which can be many times the running current.

If you use a vfd as a vfd (if you see what I mean) this problem doesn’t really exist as it’s able to ramp up smoothly (and monitor and limit its own current if required) and you don’t need the overhead if using DOL or star/delta starting.

 

[m_c]

What daleyd says.
I've used the boost VFD to replace my old rotary converter, and provide me with 3 phase.
I also have a sine wave filter after the VFD, as it's used primarily to power a CNC lathe, so I don't want any transients reaching them that could damage the controllers/drives.

This setup would start my old 2hp mill, but that was pushing the limit of the available incoming 240 supply.