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Thread: Unusable compressor
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1st Apr 2021, 07:58 PM #1Senior Member
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Unusable compressor
I have a Peerless compressor 545l/min. delivery which I run through a phase change convertor and have had no problems with it until my neighbour complained to Essential energy that the street voltage was causing problems with his solar system - they subsequently reduced the voltage in the
street which caused me not being able to start my compressor - how can I determine where the fault lies here ? is it my phase change convertor, the supply voltage to it or the compressor itself and can anyone one of you advise how I can overcome my problem as I am not very electrically wise
I could change the motor to 240V but what HP would I need (the existing is 5.5 HP) and can I be sure this will fix the problem
Essential energy in a previous look at my problem advised that the street voltage is within its tolerances so that's it
My neighbour suggested A VFD but I don't know what that would do or if it would overcome my problem
Over to you gentlemen
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1st Apr 2021, 09:56 PM #2Senior Member
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Sounds like it may have been marginal anyway, if reducing the supply voltage made that much difference.
Are you able to measure the supply voltage now, and do you know what it was?
How is the phase converter connected? If there is an extension lead, make it as short and heavy as you can.
Is the current motor 240 or 415? If it's 240 a vfd may replace the phase converter successfully, if it is 415 there are also vfd available but at a higher price.
As to what the fault is, a bit hard to tell but developing a fault at the same time the power company did work does seem not probable.
If this is all foreign, perhaps you should see if you can find a friendly industrial electrician.
Where are you located? Maybe local forumite may be able to help
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2nd Apr 2021, 12:58 AM #3
Hi Alf, Guys,
I think that I would plump for a 240 volt single phase to 440 volt three phase VFD ! Certainly it would be more cost effective !Best Regards:
Baron J.
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2nd Apr 2021, 07:22 AM #4Pink 10EE owner
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If it is a Phase Change converter, have you contacted them?
Gold, the colour of choice for the discerning person.
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2nd Apr 2021, 09:19 AM #5Member: Blue and white apron brigade
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A 5.5HP motor may represent a bit of a problem because 240V SP to 415V 3P VFD don't usually come in that size typically the biggest they get is 5kW.
Ordinarily a 5HP VFD would cope with that but because motor max HP is critical for compressors running a 5.5HP motors on a 5HP VFD might overload the VFD.
Chances are the motor is generating even more that 5.5HP for the last 20 or so PSI of its charging cycle
A few years ago I attempted to run a 4HP compressor from a 4kW (240V-415V) VFD and it would not get past 100PSI which is where the motor drew ~15A (240V) and with the max setting current of VFD of 12.5A this tripped the VFD. I got around this by using a 5HP VFD but when that motor died I replaced it with a 240V 4HP motor.
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2nd Apr 2021, 09:31 AM #6Most Valued Member
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When you say that the compressor won’t start, what actually happens when you try?
Does it try to start then trip a breaker/overload somewhere?
Do you run any other gear off the converter? If so is that behaving normally?
I find with troubleshooting it’s very tempting to jump to an initial conclusion about the source of the fault, but often it’s something completely unrelated.
I’d start with the simple things - remove the belts and make sure the motor runs happily unloaded.
If it does, then completely depressurise the tank and try again.
It could be something as simple as the unloading function on the compressor isn’t working and it’s trying to start with the full pressure load on the pump.
Steve
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2nd Apr 2021, 10:02 AM #7Senior Member
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unusable compressor
Thanks to all who answered - when connected to any other 3 ph. machines I have no problem
To be able to use the compressor I have fitted a ball valve to each head , started the comp. with valves open then closed them when comp. is up to speed - there was never any trouble until Essential energy played with the supply - both my lathe and mill give me no trouble starting- the ball vlvs are a PITA and aren't the answer
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2nd Apr 2021, 10:07 AM #8Senior Member
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2nd Apr 2021, 04:23 PM #9Senior Member
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It does sound like low voltage, which causes increased start up current which trips the phase converter.
The phase converter is a commercial unit? Does it have any adjustment to the output voltage, eg different transformer taps.
It also sounds like the compressor is starting under load. If the tank is empty does it start ok?
The other machines you mentioned are not likely to be pulling a full load on starting, or probably ever.
Do you know what your supply voltage is, and what it was?
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2nd Apr 2021, 07:32 PM #10Diamond Member
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Is there a long cable run to your shed?
That might be pushing the (now in spec?) voltage below the threshold for your converter?
(a true RMS voltmeter is your friend)
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2nd Apr 2021, 11:30 PM #11Most Valued Member
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I am far from an expert on this subject, but as a matter of interest, do you know what the supply voltage was before the change and what it is now?
My single phase compressor has an unloader built into the pressure switch so the motor gets up to speed before the load comes on, while my 3 phase unit does not, (it does however have a 10Hp 6 pole motor running a 40 CFM pump, so no shortage of Hp).
It sounds to me that you may have been running on the borderline and the reduced voltage has tipped you over the edge. Assuming your electrics all check out, then an automatic unloader valve may be your friend.
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4th Apr 2021, 08:16 PM #12Most Valued Member
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Correlation does not equal causation
If you have other equipment that runs on the phase converter and the compressor used to run on the phase converter but now doesn’t, the compressor has an issue of some description.
Line voltage is regulated within prescribed limits, any equipment you connect to line will run within those limits.
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4th Apr 2021, 09:47 PM #13Pink 10EE owner
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If it is a phase changer converter, maybe the capacitors are getting tired. I have replaced a few of mine as they started leaking. They are reasonably cheap.
Gold, the colour of choice for the discerning person.
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4th Apr 2021, 11:22 PM #14Golden Member
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What model Phase Changer is this Alf?
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5th Apr 2021, 11:27 AM #15Senior Member
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unusable compressor
Phase changer 6
Voltage is within Essential energies tolerances but they say maybe the cable dia. to the shed is a problem - long run and 10 mm. dia. cable ?
Will be contacting phase changer people this week for comment, trouble is each want to blame the other so I am going around in circles here
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