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Posted: 2/26/2015 11:39:26 PM EDT
[#1]
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High inertia loads will do that. Trying to feed a pulsed DC voltage into the primary of a transformer will cause the same problem. Quote HistoryQuoted:
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example: I had to use a motor 2 to 3 phase motor converter instead of a VFD of a bottling line, due to the extra loads it would spike current which the VFD could not handle. it may have tripping out on high DC bus voltage. a braking resistor might have solved the problem. High inertia loads will do that. A more common problem on low cost and especially older motors is that the insulation used in the motor windings is not really suitable for the voltage pulses being seen by the winding. VFDs don't produce a sine wave like normal AC current does. It produces a series of DC pulses that mimic a sine wave. The motor does not really care whether it gets a sine wave or a set of DC pulses timed correctly with the right phase shift. The pulses can have all kinds of weird effects on the waveform that actually gets to the motor. They can even bounce back and forth on the wires going to the motor and build up so they exceed the voltage rating of the motor winding insulation. A VFD rated motor will typically have much higher voltage rated insulation to accommodate this. Having said this, it takes a while for the motor to fail from this problem, and for motors that are not used much, it might not make a whole lot of difference. It is more common as the conductor length between the VFD and the motor increases, so it is a less than ideal decision to put a VFD on an older well pump motor that is a couple hundred feet down in the ground. Trying to feed a pulsed DC voltage into the primary of a transformer will cause the same problem. In the early days of transistor switched DC input inverters, [laminated power] transformers were driven [often at relatively low frequencies] as a matter of practice. For a quick data point, look at many ARRL handbooks from the period for reliable inverter construction plans for switched DC driven transformers. |
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Posted: 2/27/2015 12:56:58 AM EDT
[#2]
Ok back on topic |
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Posted: 2/27/2015 1:04:19 AM EDT
[#3]
Quote HistoryNow what does 1950's Womens' Sexual Health Aids ... Have to do with VFD's? |
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Posted: 2/27/2015 1:17:43 AM EDT
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Posted: 3/2/2015 7:25:50 PM EDT
[#5]
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Posted: 3/2/2015 8:31:01 PM EDT
[#6]
I glossed over this thread. Just wanted to put out there to be careful controlling your air compressor with a drive if it is splash lubricated. The pump may need a certain minimum RPM to lubricate itself properly.
I have more reliability issues out of my VFD-driven motors than my others. Just replaced a two baldor motors in the past month on some machinery.. Many of them ground out and fail the ole' megger test. Never realized the importance of a good ground. |
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Posted: 3/2/2015 8:35:04 PM EDT
[#7]
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I glossed over this thread. Just wanted to put out there to be careful controlling your air compressor with a drive if it is splash lubricated. The pump may need a certain minimum RPM to lubricate itself properly. I have more reliability issues out of my VFD-driven motors than my others. Just replaced a two baldor motors in the past month on some machinery.. Many of them ground out and fail the ole' megger test. Never realized the importance of a good ground. Don't overlook adding a 3 ph reactor to the VFD's output, if the VFD is designed to allow one. Low HP reactors are cheap. Also, it might be useful to scope the VFD output lines for excessive spikes that might indicate a failed/failing VFD. One VFD guru on his site mentions something like "If you aren't using a scope to diagnose VFD issues, you aren't..." ---I forget the rest... |
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Posted: 3/4/2015 1:42:11 AM EDT
[#8]
Did some of the experiment mentioned a week or so ago re running a capacitor RUN furnace blower motor using a VFD.
Tried it with a reactor in series with the 'cap/run winding' and also with the original capacitor. Took pix and more detailed data, but the total current draw was similar to running the motor without the VFD. Looked at the 3 phase output with a scope and didn't see any spikes worth noting. Took some pix of the set-up and have more data, have to finish up the BO forklift tonight. If there is any interest, I'll put up pix and data later and describe the startup current draw. |
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Posted: 3/4/2015 8:21:54 AM EDT
[#9]
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Never realized the importance of a good ground. I don't know what you mean by a "good ground", but the reality is that equipment grounding has no effect whatsoever on VFD operation. It just does not matter any one way or the other. |
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Posted: 3/4/2015 10:57:31 AM EDT
[#10]
I recently needed to reduce the start current on my 5 ton heat pump to allow off grid use. I used this, Electronic Software-Driven Soft Starters.
The manufacturer does not give a lot of details on how it functions but it did work as advertised. Measured start current was cut in half after several start cycles. Emerson climate tech sells the same unit for their AC/heat pumps http://www.emersonclimate.com/en-us/Products/Electronics_Compressors/Pages/SecureStart.aspx These should work on any single phase induction motor with minimal modifications needed to instal. |
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Posted: 3/4/2015 2:31:13 PM EDT
[#11]
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I recently needed to reduce the start current on my 5 ton heat pump to allow off grid use. I used this, Electronic Software-Driven Soft Starters. The manufacturer does not give a lot of details on how it functions but it did work as advertised. Measured start current was cut in half after several start cycles. Emerson climate tech sells the same unit for their AC/heat pumps http://www.emersonclimate.com/en-us/Products/Electronics_Compressors/Pages/SecureStart.aspx These should work on any single phase induction motor with minimal modifications needed to instal. That's interesting. Looked them up and they look to be a spin off of VFD tech, maybe pole of a VFD drive with the appropriate processor. What's the total running load of your 5 ton system? What kind of genny running it? RE the experiment above w/ the blower, I set the VFD to a five second ramp up and the motor came up smooth as silk. Also tried running the blower from the VFD without a cap or reactor in the "start/run" winding and it worked fine. Was using a HP scope and need a 100:1 probe to really see things. 10 to one probe worked but could only see half of the waveform. Maybe I'll make a resistive divider today... |
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Posted: 3/4/2015 3:03:17 PM EDT
[#12]
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That's interesting. Looked them up and they look to be a spin off of VFD tech, maybe pole of a VFD drive with the appropriate processor. What's the total running load of your 5 ton system? What kind of genny running it? RE the experiment above w/ the blower, I set the VFD to a five second ramp up and the motor came up smooth as silk. Also tried running the blower from the VFD without a cap or reactor in the "start/run" winding and it worked fine. Was using a HP scope and need a 100:1 probe to really see things. 10 to one probe worked but could only see half of the waveform. Maybe I'll make a resistive divider today... Quote HistoryQuoted:
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I recently needed to reduce the start current on my 5 ton heat pump to allow off grid use. I used this, Electronic Software-Driven Soft Starters. The manufacturer does not give a lot of details on how it functions but it did work as advertised. Measured start current was cut in half after several start cycles. Emerson climate tech sells the same unit for their AC/heat pumps http://www.emersonclimate.com/en-us/Products/Electronics_Compressors/Pages/SecureStart.aspx These should work on any single phase induction motor with minimal modifications needed to instal. That's interesting. Looked them up and they look to be a spin off of VFD tech, maybe pole of a VFD drive with the appropriate processor. What's the total running load of your 5 ton system? What kind of genny running it? RE the experiment above w/ the blower, I set the VFD to a five second ramp up and the motor came up smooth as silk. Also tried running the blower from the VFD without a cap or reactor in the "start/run" winding and it worked fine. Was using a HP scope and need a 100:1 probe to really see things. 10 to one probe worked but could only see half of the waveform. Maybe I'll make a resistive divider today... I have a PV system with 30 KWH battery backup & grid tied. It is an Outback Radian system with 2 Radian inverters and 30 275W solar panels. The radian inverters allow me to hook up my Honda EU6500 generator as an additional AC input. This allows me to set the max amp draw from the generator so it never sees an over load situation. If I'm running the generator and the peak demand goes over the set point for the gen. then the inverters pull from the battery bank and/or solar panels. The battery bank can provide a peak of 25KVA. My heat pump compressor is rated @ 29 RLA and 148 LRA. The problem was the LRA. At 148 A 220V the peak draw is ~ 30KVA and with two Radian inverters rated at 8 KW cont/16KW peak (each) I was pushing the limit on the inverters. Now the peak start current is ~70A so I'm well within the inverters capacity. 
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Posted: 3/4/2015 4:03:08 PM EDT
[#13]
That's quite a system Rich... Holy cow...
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Posted: 3/4/2015 6:34:51 PM EDT
[#14]
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That's quite a system Rich... Holy cow... It's brand new, just finished the installation last month. Since I'm in a prime solar location (AZ) this system will generate as much power as I use on a yearly average or maybe a bit extra. Add in the 1000 gallon propane tank buried in the yard and high output deep well I'm ready for the SHTF. 
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Posted: 3/4/2015 6:49:22 PM EDT
[#15]
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It's brand new, just finished the installation last month. Since I'm in a prime solar location (AZ) this system will generate as much power as I use on a yearly average or maybe a bit extra. Add in the 1000 gallon propane tank buried in the yard and high output deep well I'm ready for the SHTF. Quote HistoryQuoted:
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That's quite a system Rich... Holy cow... It's brand new, just finished the installation last month. Since I'm in a prime solar location (AZ) this system will generate as much power as I use on a yearly average or maybe a bit extra. Add in the 1000 gallon propane tank buried in the yard and high output deep well I'm ready for the SHTF. What kinds of batteries are you using? |
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Posted: 3/4/2015 6:55:54 PM EDT
[#16]
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What kinds of batteries are you using? Quote HistoryQuoted:
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That's quite a system Rich... Holy cow... It's brand new, just finished the installation last month. Since I'm in a prime solar location (AZ) this system will generate as much power as I use on a yearly average or maybe a bit extra. Add in the 1000 gallon propane tank buried in the yard and high output deep well I'm ready for the SHTF. What kinds of batteries are you using? EnergyCell GH AGM batteries. They are rebranded PowerSafe SBS EON Batteries designed for long life float service. |
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Posted: 4/20/2015 11:34:19 AM EDT
[#17]
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EnergyCell GH AGM batteries. They are rebranded PowerSafe SBS EON Batteries designed for long life float service. Quote HistoryQuoted:
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That's quite a system Rich... Holy cow... It's brand new, just finished the installation last month. Since I'm in a prime solar location (AZ) this system will generate as much power as I use on a yearly average or maybe a bit extra. Add in the 1000 gallon propane tank buried in the yard and high output deep well I'm ready for the SHTF. What kinds of batteries are you using? EnergyCell GH AGM batteries. They are rebranded PowerSafe SBS EON Batteries designed for long life float service. Wow Rich, that's a lot of battery storage in a compact package! 
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Posted: 4/20/2015 11:38:48 AM EDT
[#18]
Wanted to mention that there was a low surge current when ramping up a 240 vac cap run furnace blower motor with just two legs of the HY inverter connected to the motor.
The input was 240 vac as well. Pretty neat to watch the current to slowly rise as the blower spins up over a couple seconds.
So, for folks who have genny's with issues starting a motor load of some sort, maybe ramping it with an inexpensive inverter might help. See experiment several posts above. |
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Posted: 4/20/2015 11:57:32 AM EDT
[#19]
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Wow Rich, that's a lot of battery storage in a compact package!
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That's quite a system Rich... Holy cow... It's brand new, just finished the installation last month. Since I'm in a prime solar location (AZ) this system will generate as much power as I use on a yearly average or maybe a bit extra. Add in the 1000 gallon propane tank buried in the yard and high output deep well I'm ready for the SHTF. What kinds of batteries are you using? EnergyCell GH AGM batteries. They are rebranded PowerSafe SBS EON Batteries designed for long life float service. Wow Rich, that's a lot of battery storage in a compact package!
They weren't cheap but they are high quality AGMs. Over the last 29 days (mid March - mid April) the PV system has produced 1250 kWh, about 43 kWh/day average. That's from 8.25kw of panels, this thing will be cooking come June-July. 
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Posted: 4/20/2015 12:08:18 PM EDT
[#20]
You should start selling juice to the neighborhood!
43kWh/day is nice to have. We've got 4 230 watt panels facing SE and 3 facing SW on the barn and I see about 8+ kWh/day on the best days. I set them for a good slope to shed snow in the winter and don't worry abt resetting them in the summer. Thinking about pulling some from the "SHTF Panels to Trade for Food" stash and adding to the 7. Maybe 3 or 6 more this year. Which means adding 1 or 2 more Outbacks. |
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Posted: 4/20/2015 12:20:32 PM EDT
[#21]
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You should start selling juice to the neighborhood! 43kWh/day is nice to have. We've got 4 230 watt panels facing SE and 3 facing SW on the barn and I see about 8+ kWh/day on the best days. I set them for a good slope to shed snow in the winter and don't worry abt resetting them in the summer. Thinking about pulling some from the "SHTF Panels to Trade for Food" stash and adding to the 7. I push the excess to the grid and take it back when the sun don't shine. Arizona is a net metering state so the utility company acts as my "Big battery". The "little batteries" I have are for grid down events and they are necessary to run the Radian inverters in grid tied mode. |
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Posted: 4/20/2015 12:42:47 PM EDT
[#22]
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I push the excess to the grid and take it back when the sun don't shine. Arizona is a net metering state so the utility company acts as my "Big battery". The "little batteries" I have are for grid down events and they are necessary to run the Radian inverters in grid tied mode. Quote HistoryQuoted:
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You should start selling juice to the neighborhood! 43kWh/day is nice to have. We've got 4 230 watt panels facing SE and 3 facing SW on the barn and I see about 8+ kWh/day on the best days. I set them for a good slope to shed snow in the winter and don't worry abt resetting them in the summer. Thinking about pulling some from the "SHTF Panels to Trade for Food" stash and adding to the 7. I push the excess to the grid and take it back when the sun don't shine. Arizona is a net metering state so the utility company acts as my "Big battery". The "little batteries" I have are for grid down events and they are necessary to run the Radian inverters in grid tied mode. I meant by running extension cords to your neighbors with suicide plugs on them...
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