DC-AC Power Inverters DANGER
Question:
I have been looking for a replacement of my older DC-AC inverter to go camping and hook up inside my truck and wired up as code with the natural at ground and case ground potential. Going over several DC-AC Sinewave Power inverters there seems like there is only a few that DO a good job without noise riding on the output, and provide the kind of output that I need. The requirement I was looking for was that the NATURAL of the AC out must be at case ground. I looked at some of the lower cost ( WAGAN sinewave) and others inverters, and their so called natural was floating above ground as part of the sinewave. The reason is that when I hooked these inverters up to my camping trailer that normally plugs into the camping site AC power the AC line going to the Camper is hooked up as it should be, natural and ground is hooked to camper ground as required by code. I used this to power the small AC lights and other devices plugged into the inside AC sockets running from the Trucks DC battery supply. Now here is the problem that is very DANGEROUS, and should be looked into. From the cheaper modified sine wave or puresinewave inverters from many of manufactures, the NATURAL side of the AC out is HOT ( part of the waveform to save a small cost in building) , the problem is that if someone touches the truck, and the camper next to it guess what BAD SHOCK. Keep this in mind if you are hooking the inverter to something wired external. Some of the Xantrex Modified Sine Wave Inverters ,Prowatt,and Portawattz and their Prosine series,have this with grounded natural output, and EXELTECK seem to also has a good grounded AC natural with a clean sinewave output. I do not know about Samlex sinewave series but I am looking for more input.
Response:
I’d like to hear more input on this. It would seem from your description that some of these inverters are providing what is known as "balanced AC", which is actually desirable in some situations. As long as the design of the inverter is transformer isolated, and I think they all are, what you are referring to is a floating AC waveform with no ground reference. This is not in itself a shock hazard, and you could make the neutral-ground bond yourself. I’m not trying to be authoritative, these are just some informal thoughts, and I’m curious what other people have to say. – Hide quoted text — Show quoted text – > I have been looking for a replacement of my older DC-AC inverter to go > camping and hook up inside my truck and wired up as code with the natural at > ground and case ground potential. Going over several DC-AC Sinewave Power > inverters there seems like there is only a few that DO a good job without > noise riding on the output, and provide the kind of output that I need. The > requirement I was looking for was that the NATURAL of the AC out must be at > case ground. I looked at some of the lower cost ( WAGAN sinewave) and others > inverters, and their so called natural was floating above ground as part of > the sinewave. The reason is that when I hooked these inverters up to my > camping trailer that normally plugs into the camping site AC power the AC > line going to the Camper is hooked up as it should be, natural and ground is > hooked to camper ground as required by code. I used this to power the small > AC lights and other devices plugged into the inside AC sockets running from > the Trucks DC battery supply. Now here is the problem that is very > DANGEROUS, and should be looked into. From the cheaper modified sine wave > or puresinewave inverters from many of manufactures, the NATURAL side of the > AC out is HOT ( part of the waveform to save a small cost in building) , the > problem is that if someone touches the truck, and the camper next to it > guess what BAD SHOCK. Keep this in mind if you are hooking the inverter to > something wired external. Some of the Xantrex Modified Sine Wave Inverters > ,Prowatt,and Portawattz and their Prosine series,have this with grounded > natural output, and EXELTECK seem to also has a good grounded AC natural > with a clean sinewave output. I do not know about Samlex sinewave series but > I am looking for more input.
Response:
Robert MOST of the inverters are not transformer isolated from the DC input, as I have only one 1000 Watt that is, if they were all isolated I would hook the out put AC jack with the netural to ground. Its in the cost to make the inverters as cheap as possible and actually it is not that much more to provide the correct grounding AC output. Most builders drive the AC socket from a H bridge switching supply witch makes both sides of the AC output line inverters HOT compaired to the incomming DC ground. I might mention that I am talking about the small 50- some 1000 Watt inverters, not the big ones. Some manifactures do development where the AC Hot side does swing above and below ground pontential as in a normal AC jack in the home.
> I’d like to hear more input on this. > It would seem from your description that some of these inverters are > providing what is known as "balanced AC", which is actually desirable in > some situations. > As long as the design of the inverter is transformer isolated, and I think > they all are, what you are referring to is a floating AC waveform with no > ground reference. This is not in itself a shock hazard, and you could make > the neutral-ground bond yourself. > I’m not trying to be authoritative, these are just some informal thoughts, > and I’m curious what other people have to say.
– Hide quoted text — Show quoted text -> I have been looking for a replacement of my older DC-AC inverter to go > camping and hook up inside my truck and wired up as code with the natural > at > ground and case ground potential. Going over several DC-AC Sinewave Power > inverters there seems like there is only a few that DO a good job without > noise riding on the output, and provide the kind of output that I need. > The > requirement I was looking for was that the NATURAL of the AC out must be > at > case ground. I looked at some of the lower cost ( WAGAN sinewave) and > others > inverters, and their so called natural was floating above ground as part > of > the sinewave. The reason is that when I hooked these inverters up to my > camping trailer that normally plugs into the camping site AC power the AC > line going to the Camper is hooked up as it should be, natural and ground > is > hooked to camper ground as required by code. I used this to power the > small > AC lights and other devices plugged into the inside AC sockets running > from > the Trucks DC battery supply. Now here is the problem that is very > DANGEROUS, and should be looked into. From the cheaper modified sine > wave > or puresinewave inverters from many of manufactures, the NATURAL side of > the > AC out is HOT ( part of the waveform to save a small cost in building) , > the > problem is that if someone touches the truck, and the camper next to it > guess what BAD SHOCK. Keep this in mind if you are hooking the inverter to > something wired external. Some of the Xantrex Modified Sine Wave > Inverters > ,Prowatt,and Portawattz and their Prosine series,have this with grounded > natural output, and EXELTECK seem to also has a good grounded AC natural > with a clean sinewave output. I do not know about Samlex sinewave series > but > I am looking for more input.
Response:
Big spelling mistake. ITS NEUTRAL not natural.
Response:
Every inverter I’ve ever seen has had a transformer in it.It *has* to to transform 12V (24,48,etc) to 120Vac. 12Vdc comes in,goes (pulsed at high freq.) through a set of (HEX)FETS,stepped up to ~150-200V by a small ferrite transformer,rectified(now back to DC),filtered with a large cap, and gets chopped up by an H-bridge at 50/60hz (back to AC). Thats the usual setup for a cheap square/"modified sinewave" inverter. I’d imagine a sinewave inverter would be similar,with the exception of the H-bridge,and the drive signal(s) to it. Now,wether or not it’s designed with a floating output or grounded neutral,etc. is another story.. Probably varies alot by manufacturer. – Hide quoted text — Show quoted text – > Robert MOST of the inverters are not transformer isolated from the DC > input, as I have only one 1000 Watt that is, if they were all isolated I > would hook the out put AC jack with the netural to ground. Its in the cost > to make the inverters as cheap as possible and actually it is not that much > more to provide the correct grounding AC output. Most builders drive the AC > socket from a H bridge switching supply witch makes both sides of the AC > output line inverters HOT compaired to the incomming DC ground. > I might mention that I am talking about the small 50- > some 1000 Watt inverters, not the big ones. > Some manifactures do development where the AC Hot side does swing above and > below ground pontential as in a normal AC jack in the home. >I’d like to hear more input on this. >It would seem from your description that some of these inverters are >providing what is known as "balanced AC", which is actually desirable in >some situations. >As long as the design of the inverter is transformer isolated, and I think >they all are, what you are referring to is a floating AC waveform with no >ground reference. This is not in itself a shock hazard, and you could make >the neutral-ground bond yourself. >I’m not trying to be authoritative, these are just some informal thoughts, >and I’m curious what other people have to say. >>I have been looking for a replacement of my older DC-AC inverter to go >>camping and hook up inside my truck and wired up as code with the > natural >at >>ground and case ground potential. Going over several DC-AC Sinewave > Power >>inverters there seems like there is only a few that DO a good job > without >>noise riding on the output, and provide the kind of output that I need. >The >>requirement I was looking for was that the NATURAL of the AC out must be >at >>case ground. I looked at some of the lower cost ( WAGAN sinewave) and >others >>inverters, and their so called natural was floating above ground as part >of >>the sinewave. The reason is that when I hooked these inverters up to my >>camping trailer that normally plugs into the camping site AC power the > AC >>line going to the Camper is hooked up as it should be, natural and > ground >is >>hooked to camper ground as required by code. I used this to power the >small >>AC lights and other devices plugged into the inside AC sockets running >from >>the Trucks DC battery supply. Now here is the problem that is very >>DANGEROUS, and should be looked into. From the cheaper modified sine >wave >>or puresinewave inverters from many of manufactures, the NATURAL side of >the >>AC out is HOT ( part of the waveform to save a small cost in building) , >the >>problem is that if someone touches the truck, and the camper next to it >>guess what BAD SHOCK. Keep this in mind if you are hooking the inverter > to >>something wired external. Some of the Xantrex Modified Sine Wave >Inverters >>,Prowatt,and Portawattz and their Prosine series,have this with grounded >>natural output, and EXELTECK seem to also has a good grounded AC natural >>with a clean sinewave output. I do not know about Samlex sinewave series >but >>I am looking for more input.
Response:
> Every inverter I’ve ever seen has had a transformer in it.It *has* to to > transform 12V (24,48,etc) to 120Vac. > 12Vdc comes in,goes (pulsed at high freq.) through a set of > (HEX)FETS,stepped up to ~150-200V by a small ferrite > transformer,rectified(now back to DC),filtered with a large cap, and > gets chopped up by an H-bridge at 50/60hz (back to AC).
Thats right but the HV CAP in some inverters are grounded to the input DC supply to have a referenct to adjust the High Voltage Regulation to. If they used optico isolators for their HI Voltage feedback with it woulb be possible for isolation. Now the problem is an isolated supply for the switching transistors . Rember the High Voltage FETS drive must come from somewhere, and if it is powered from ICs or transistor drivers they must get their power from somewhere. Most use the incomming DC and regulate to power them. Now we are not isolated. I did not say there was no transformers used but some inverters are NOT isolated. I am stating that there is a possibilty for a shock hazord on some inverters. Here you are going off like you know so damn much and trying to dispute my findings, but I bet you would not like touching my inverter as I had noted it will SHOCK YOU. ITS NOT ISOLATED. Its HV supply is referanced to the incomming DC leads. I am trying to pass some info along to help out. Hell man I have been desinging circuits since 1972 in all fields. Try it some models and touch one side of the AC out and case or DC ground at the same time if it is so isolated as you state then you will feel nothing Good luck on some units. Then tell us all about it before you go off . One way to provide the AC out is to have a + 180and a — 180 volt supply from ground pontental ,and switch the AC HOT lead from these voltage levels either modifed sine wave or pure sinewave. This way the AC ground would be where it should be. – Hide quoted text — Show quoted text -> Thats the usual setup for a cheap square/"modified sinewave" inverter. > I’d imagine a sinewave inverter would be similar,with the exception of > the H-bridge,and the drive signal(s) to it. > Now,wether or not it’s designed with a floating output or grounded > neutral,etc. is another story.. Probably varies alot by manufacturer. > Robert MOST of the inverters are not transformer isolated from the DC > input, as I have only one 1000 Watt that is, if they were all isolated I > would hook the out put AC jack with the netural to ground. Its in the cost > to make the inverters as cheap as possible and actually it is not that much > more to provide the correct grounding AC output. Most builders drive the AC > socket from a H bridge switching supply witch makes both sides of the AC > output line inverters HOT compaired to the incomming DC ground. > I might mention that I am talking about the small 50- > some 1000 Watt inverters, not the big ones. > Some manifactures do development where the AC Hot side does swing above and > below ground pontential as in a normal AC jack in the home. >>I’d like to hear more input on this. >>It would seem from your description that some of these inverters are >>providing what is known as "balanced AC", which is actually desirable in >>some situations. >>As long as the design of the inverter is transformer isolated, and I think >>they all are, what you are referring to is a floating AC waveform with no >>ground reference. This is not in itself a shock hazard, and you could make >>the neutral-ground bond yourself. >>I’m not trying to be authoritative, these are just some informal thoughts, >>and I’m curious what other people have to say. >>>I have been looking for a replacement of my older DC-AC inverter to go >>>camping and hook up inside my truck and wired up as code with the > natural >>at >>>ground and case ground potential. Going over several DC-AC Sinewave > Power >>>inverters there seems like there is only a few that DO a good job > without >>>noise riding on the output, and provide the kind of output that I need. >>The >>>requirement I was looking for was that the NATURAL of the AC out must be >>at >>>case ground. I looked at some of the lower cost ( WAGAN sinewave) and >>others >>>inverters, and their so called natural was floating above ground as part >>of >>>the sinewave. The reason is that when I hooked these inverters up to my >>>camping trailer that normally plugs into the camping site AC power the > AC >>>line going to the Camper is hooked up as it should be, natural and > ground >>is >>>hooked to camper ground as required by code. I used this to power the >>small >>>AC lights and other devices plugged into the inside AC sockets running >>from >>>the Trucks DC battery supply. Now here is the problem that is very >>>DANGEROUS, and should be looked into. From the cheaper modified sine >>wave >>>or puresinewave inverters from many of manufactures, the NATURAL side of >>the >>>AC out is HOT ( part of the waveform to save a small cost in building) , >>the >>>problem is that if someone touches the truck, and the camper next to it >>>guess what BAD SHOCK. Keep this in mind if you are hooking the inverter > to >>>something wired external. Some of the Xantrex Modified Sine Wave >>Inverters >>>,Prowatt,and Portawattz and their Prosine series,have this with grounded >>>natural output, and EXELTECK seem to also has a good grounded AC natural >>>with a clean sinewave output. I do not know about Samlex sinewave series >>but >>>I am looking for more input.
Response:
>>Every inverter I’ve ever seen has had a transformer in it.It *has* to to >transform 12V (24,48,etc) to 120Vac. >12Vdc comes in,goes (pulsed at high freq.) through a set of >(HEX)FETS,stepped up to ~150-200V by a small ferrite >transformer,rectified(now back to DC),filtered with a large cap, and >gets chopped up by an H-bridge at 50/60hz (back to AC). > Thats right but the HV CAP in some inverters are grounded to the input DC > supply to have a referenct to adjust the High Voltage Regulation to.
Exactly. and now your output is xxx volts above the input GND. > If they used optico isolators for their HI Voltage feedback with it woulb be > possible for isolation. Now the problem is an isolated supply for the > switching transistors . Rember the High Voltage FETS drive must come from > somewhere, and if it is powered from ICs or transistor drivers they must get > their power from somewhere. Most use the incomming DC and regulate to power > them. Now we are not isolated.
Indeed,most use a 7812 and/or 7805 to get the voltages for the driver IC’s,and circuitry straight from the DC input..And yep,isolation is gone,unless they used optoisolators like you say.. > I did not say there was no transformers used but some inverters are NOT > isolated. I am stating that there is a possibilty for a shock hazord on some > inverters. Here you are going off like you know so damn much and trying to > dispute my findings, but I bet you would not like touching my inverter as I > had noted it will SHOCK YOU. ITS NOT ISOLATED. Its HV supply is referanced > to the incomming DC leads. > I am trying to pass some info along to help out. Hell man I have been > desinging circuits since 1972 in all fields.
You said that most inverters do not have transformer isolation..The transformers are isolated,but the rest of the circuit may not be,depending on how it was designed..(above notes..) (moot point,if the output isn’t isolated anyways.) I havn’t been in electronics that long,but I’ve "been around the block" so to speak. > Try it some models and touch one side of the AC out and case or DC ground > at the same time if it is so isolated as you state then you will feel > nothing Good luck on some units. > Then tell us all about it before you go off . > One way to provide the AC out is to have a + 180and a — 180 volt supply > from ground pontental ,and switch the AC HOT lead from these voltage levels > either modifed sine wave or pure sinewave. This way the AC ground would be > where it should be.
Yes,that would work,and I think alot of larger sinewave inverters may do just that,but i’m not sure.. – Hide quoted text — Show quoted text ->Thats the usual setup for a cheap square/"modified sinewave" inverter. >I’d imagine a sinewave inverter would be similar,with the exception of >the H-bridge,and the drive signal(s) to it. >Now,wether or not it’s designed with a floating output or grounded >neutral,etc. is another story.. Probably varies alot by manufacturer. >>Robert MOST of the inverters are not transformer isolated from the DC >>input, as I have only one 1000 Watt that is, if they were all isolated I >>would hook the out put AC jack with the netural to ground. Its in the > cost >>to make the inverters as cheap as possible and actually it is not that > much >>more to provide the correct grounding AC output. Most builders drive > the AC >>socket from a H bridge switching supply witch makes both sides of the AC >>output line inverters HOT compaired to the incomming DC ground. >> I might mention that I am talking about the small 50- >>some 1000 Watt inverters, not the big ones. >>Some manifactures do development where the AC Hot side does swing above > and >>below ground pontential as in a normal AC jack in the home. >>>I’d like to hear more input on this. >>>It would seem from your description that some of these inverters are >>>providing what is known as "balanced AC", which is actually desirable in >>>some situations. >>>As long as the design of the inverter is transformer isolated, and I > think >>>they all are, what you are referring to is a floating AC waveform with > no >>>ground reference. This is not in itself a shock hazard, and you could > make >>>the neutral-ground bond yourself. >>>I’m not trying to be authoritative, these are just some informal > thoughts, >>>and I’m curious what other people have to say. >>>>I have been looking for a replacement of my older DC-AC inverter to go >>>>camping and hook up inside my truck and wired up as code with the >>natural >>>at >>>>ground and case ground potential. Going over several DC-AC Sinewave >>Power >>>>inverters there seems like there is only a few that DO a good job >>without >>>>noise riding on the output, and provide the kind of output that I need. >>>The >>>>requirement I was looking for was that the NATURAL of the AC out must > be >>>at >>>>case ground. I looked at some of the lower cost ( WAGAN sinewave) and >>>others >>>>inverters, and their so called natural was floating above ground as > part >>>of >>>>the sinewave. The reason is that when I hooked these inverters up to my >>>>camping trailer that normally plugs into the camping site AC power the >>AC >>>>line going to the Camper is hooked up as it should be, natural and >>ground >>>is >>>>hooked to camper ground as required by code. I used this to power the >>>small >>>>AC lights and other devices plugged into the inside AC sockets running >>>from >>>>the Trucks DC battery supply. Now here is the problem that is very >>>>DANGEROUS, and should be looked into. From the cheaper modified sine >>>wave >>>>or puresinewave inverters from many of manufactures, the NATURAL side > of >>>the >>>>AC out is HOT ( part of the waveform to save a small cost in building) > , >>>the >>>>problem is that if someone touches the truck, and the camper next to it >>>>guess what BAD SHOCK. Keep this in mind if you are hooking the inverter >>to >>>>something wired external. Some of the Xantrex Modified Sine Wave >>>Inverters >>>>,Prowatt,and Portawattz and their Prosine series,have this with > grounded >>>>natural output, and EXELTECK seem to also has a good grounded AC > natural >>>>with a clean sinewave output. I do not know about Samlex sinewave > series >>>but >>>>I am looking for more input.
Response:
This a common problem with low cost, under 1000 watt inverters. Some of the inverters, such as the Xantrex Portawattz 600, have a warning in the user manual (but not on the box or on-line data) that they are not to be used in conventional building wiring situations wherein the neutral and ground are connected. Connecting neutral to ground will destroy the inverter when input power is applied and this damage is not covered under warranty. I found the same problem with Coleman inverters, even after asking factory engineers if the neutral could be grounded to the battery negative and getting a email stating that it was okay to do so. At least a copy of the email resulted in a refund after the inverter failed. None of these low cost inverters are UL listed. Most of these inverters use a circuit that boosts the +12V (or +24V) input to about 160 volts using a switchmode up converter, then uses a H-bridge of power FETs to switch this to the output to form a square wave AC waveform. This is not isolated from the DC input. – Hide quoted text — Show quoted text – > I have been looking for a replacement of my older DC-AC inverter to go >camping and hook up inside my truck and wired up as code with the natural at >ground and case ground potential. Going over several DC-AC Sinewave Power >inverters there seems like there is only a few that DO a good job without >noise riding on the output, and provide the kind of output that I need. The >requirement I was looking for was that the NATURAL of the AC out must be at >case ground. I looked at some of the lower cost ( WAGAN sinewave) and others >inverters, and their so called natural was floating above ground as part of >the sinewave. The reason is that when I hooked these inverters up to my >camping trailer that normally plugs into the camping site AC power the AC >line going to the Camper is hooked up as it should be, natural and ground is >hooked to camper ground as required by code. I used this to power the small >AC lights and other devices plugged into the inside AC sockets running from >the Trucks DC battery supply. Now here is the problem that is very >DANGEROUS, and should be looked into. From the cheaper modified sine wave >or puresinewave inverters from many of manufactures, the NATURAL side of the >AC out is HOT ( part of the waveform to save a small cost in building) , the >problem is that if someone touches the truck, and the camper next to it >guess what BAD SHOCK. Keep this in mind if you are hooking the inverter to >something wired external. Some of the Xantrex Modified Sine Wave Inverters >,Prowatt,and Portawattz and their Prosine series,have this with grounded >natural output, and EXELTECK seem to also has a good grounded AC natural >with a clean sinewave output. I do not know about Samlex sinewave series but >I am looking for more input.
Bill Kaszeta Photovoltaic Resources Int’l Tempe Arizona USA
Response:
Thanks for your input Bill as I have found the same from allot of the other types. In my old manual the inverter never mentioned anything about any external hookups. My 1500w Portawattz modifed sinewavw inverter is one of the best I have seen in the build quality, manual, and also having the output GFCI protected. Very good Unit . Now I am trying to find a lower wattage sinewave unit ( 250-400) that is not too big but with a safe output, netural grounded. I think ELEXTECH makes it , but you pay the cost. MY wife or others that might come along and might use it in a camping trip I fell safer. It comes down to cost in building them,H bridge outputs are a little cheaper to build but parts cost ( cost in China $.35- $1.00 per unit) is just a small amount for safety, maybe just a few more parts could have done it right. – Hide quoted text — Show quoted text -> This a common problem with low cost, under 1000 watt inverters. > Some of the inverters, such as the Xantrex Portawattz 600, have a > warning in the user manual (but not on the box or on-line data) that > they are not to be used in conventional building wiring situations > wherein the neutral and ground are connected. Connecting neutral > to ground will destroy the inverter when input power is applied and this > damage is not covered under warranty. > I found the same problem with Coleman inverters, even after asking > factory engineers if the neutral could be grounded to the battery > negative and getting a email stating that it was okay to do so. At least > a copy of the email resulted in a refund after the inverter failed. > None of these low cost inverters are UL listed. > Most of these inverters use a circuit that boosts the +12V (or +24V) input > to about 160 volts using a switchmode up converter, then uses a > H-bridge of power FETs to switch this to the output to form a square > wave AC waveform. This is not isolated from the DC input. > I have been looking for a replacement of my older DC-AC inverter to go >camping and hook up inside my truck and wired up as code with the natural at >ground and case ground potential. Going over several DC-AC Sinewave Power >inverters there seems like there is only a few that DO a good job without >noise riding on the output, and provide the kind of output that I need. The >requirement I was looking for was that the NATURAL of the AC out must be at >case ground. I looked at some of the lower cost ( WAGAN sinewave) and others >inverters, and their so called natural was floating above ground as part of >the sinewave. The reason is that when I hooked these inverters up to my >camping trailer that normally plugs into the camping site AC power the AC >line going to the Camper is hooked up as it should be, natural and ground is >hooked to camper ground as required by code. I used this to power the small >AC lights and other devices plugged into the inside AC sockets running from >the Trucks DC battery supply. Now here is the problem that is very >DANGEROUS, and should be looked into. From the cheaper modified sine wave >or puresinewave inverters from many of manufactures, the NATURAL side of the >AC out is HOT ( part of the waveform to save a small cost in building) , the >problem is that if someone touches the truck, and the camper next to it >guess what BAD SHOCK. Keep this in mind if you are hooking the inverter to >something wired external. Some of the Xantrex Modified Sine Wave Inverters >,Prowatt,and Portawattz and their Prosine series,have this with grounded >natural output, and EXELTECK seem to also has a good grounded AC natural >with a clean sinewave output. I do not know about Samlex sinewave series but >I am looking for more input. > Bill Kaszeta > Photovoltaic Resources Int’l > Tempe Arizona USA
Response:
- Hide quoted text — Show quoted text – >Thanks for your input Bill as I have found the same from allot of the other >types. In my old manual the inverter never mentioned anything about any >external hookups. My 1500w Portawattz modifed sinewavw inverter is one of >the best I have seen in the build quality, manual, and also having the >output GFCI protected. Very good Unit . Now I am trying to find a lower >wattage sinewave unit ( 250-400) that is not too big but with a safe output, >netural grounded. I think ELEXTECH >makes it , but you pay the cost. > MY wife or others that might come along and might use it in a camping trip >I fell safer. >It comes down to cost in building them,H bridge outputs are a little cheaper >to build but parts cost ( cost in China $.35- $1.00 per unit) is just a >small amount for safety, maybe just a few more parts could have done it >right.
FYI the Samlex sine wave units are transformer isolated, and at least some of their smaller non-sine units are as well. I bought a refurb Samlex 600W non-sine to replace a 300W non-isolated unit for my friend’s little cabin set-up. I have a Samlex 600W sine unit that I bought just to get a little clean sine power for some audio applications. Then almost immediately an opportunity arose to get into a sine inverter big enough to handle the whole house, but I haven’t wired it in yet. The Samlex has been doing a fine job and is a real bargain IMHO. The only precaution is that, if you’re using temperature-compensated battery charging and your batteries are subjected to cool temperatures, the Samlex’s max input voltage of 15.0 is going to be a problem. It squawks and shuts down, but according to the manual it can still be damaged if overvoltage persists. Some renewable energy equipment dealers hammered this point home to Samlex until they finally got the joke, and they will likely update the design to provide higher max input voltage in future if they haven’t already. In an RV / cabin / non temp-compensated charging scenario this wouldn’t be an issue. Cheers, -=s – Hide quoted text — Show quoted text -> This a common problem with low cost, under 1000 watt inverters. > Some of the inverters, such as the Xantrex Portawattz 600, have a > warning in the user manual (but not on the box or on-line data) that > they are not to be used in conventional building wiring situations > wherein the neutral and ground are connected. Connecting neutral > to ground will destroy the inverter when input power is applied and this > damage is not covered under warranty. > I found the same problem with Coleman inverters, even after asking > factory engineers if the neutral could be grounded to the battery > negative and getting a email stating that it was okay to do so. At least > a copy of the email resulted in a refund after the inverter failed. > None of these low cost inverters are UL listed. > Most of these inverters use a circuit that boosts the +12V (or +24V) input > to about 160 volts using a switchmode up converter, then uses a > H-bridge of power FETs to switch this to the output to form a square > wave AC waveform. This is not isolated from the DC input. > > I have been looking for a replacement of my older DC-AC inverter to go > >camping and hook up inside my truck and wired up as code with the natural >at > >ground and case ground potential. Going over several DC-AC Sinewave Power > >inverters there seems like there is only a few that DO a good job without > >noise riding on the output, and provide the kind of output that I need. >The > >requirement I was looking for was that the NATURAL of the AC out must be >at > >case ground. I looked at some of the lower cost ( WAGAN sinewave) and >others > >inverters, and their so called natural was floating above ground as part >of > >the sinewave. The reason is that when I hooked these inverters up to my > >camping trailer that normally plugs into the camping site AC power the AC > >line going to the Camper is hooked up as it should be, natural and ground >is > >hooked to camper ground as required by code. I used this to power the >small > >AC lights and other devices plugged into the inside AC sockets running >from > >the Trucks DC battery supply. Now here is the problem that is very > >DANGEROUS, and should be looked into. From the cheaper modified sine >wave > >or puresinewave inverters from many of manufactures, the NATURAL side of >the > >AC out is HOT ( part of the waveform to save a small cost in building) , >the > >problem is that if someone touches the truck, and the camper next to it > >guess what BAD SHOCK. Keep this in mind if you are hooking the inverter >to > >something wired external. Some of the Xantrex Modified Sine Wave >Inverters > >,Prowatt,and Portawattz and their Prosine series,have this with grounded > >natural output, and EXELTECK seem to also has a good grounded AC natural > >with a clean sinewave output. I do not know about Samlex sinewave series >but > >I am looking for more input. > Bill Kaszeta > Photovoltaic Resources Int’l > Tempe Arizona USA
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[snip] I do not know about Samlex sinewave series but > I am looking for more input.
I just checked my Samlex S1500 sinewave unit, and neutral is bonded to ground.
Response:
> [snip] > I do not know about Samlex sinewave series but > I am looking for more input. > I just checked my Samlex S1500 sinewave unit, and neutral is bonded to > ground.
The AIM inverters will either smoke or shut down if there is a connection to ground.
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