Contactor Overload Relay not working - need help
#31
The phase converter is protected by the 30 amp circuit breaker.  The jointer is protected by 20 amp fuses, if I remember what I saw correctly, and the motor by the overload relay.  Are you suggesting the overload relay should be rated higher than 13 amps?  That's 120% of the motor FLA.

John
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#32
I would say the 9-13 amp unit is the correct unit for your motor rated at 11.2 amps.   As blackhat said check the amperage under a heavy load.    Remember you do not have a 5 hp motor when it is run on a phase converter.
 The overloads will allow for starting current and short overloading times but 120% is pushing it a little.    Roly
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#33
No. if the motor is rated at 13 and is drawing that under load, I would prefer an OL that has 13 in the lower half of its rating, say an 11 to 16 over an 8 to 14. I was just wondering if this OL was redundant. It's not
Blackhat

Bad experiences come from poor decisions. So do good stories. 


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#34
Thanks guys.  So I just checked my photo of the motor plate again and see the motor draws 12.2 amps at FL, not 11.2 as I said.  Also, the motor has a SF of 1.25.  Looking at Telemechanique's information, they make a 9 - 13 amp OL relay and a 12 - 18 amp one. 

1.25 x 12.2 = 15.25 amps so it makes sense to me that that should be the max. setting of the OL relay, which would favor picking the 12 - 18 amp one.  The motor is drawing 9 - 10 amps under no load.  What it is under heavy load I don't know, but we could measure it if that's critical.  Seems like the 12 - 18 relay set at 12.2, with the capability to set it higher if needed, is the right choice.  

Which would you pick?  Thanks.

JOhn
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#35
With the new info I will agree the 12 to 18 would be the best.  Remember it is not a 5 hp motor with the phase converter, it is a  3.3 hp motor.   It will be easy to overload it so don't set it above the 125% number of 15 A.    Roly
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#36
Is this a balanced, or an unbalanced, static converter? An unbalanced is just a motor starter, while a balanced will provide something better, but not as good as, a rotary converter, which itself is just a balanced static with a rotary transformer. In either case, the current will not be the same in all three legs, with one leg especially low. The capacitor values are selected for full-load operating conditions, and no=load values can be all over the place. It's not a good situation, but if you use a large enough motor and don't push it too hard, they work. But without the idler motor (rotary transformer), you're single-phasing the motor, or close to it if the capacitors stay in the circuit the whole time.

But either way, you don't want to exceed the rated current on any lead, as the windings don't know what's going on other than the heat generated within, which is a function of their impedance and the current flow. So look at the worst-case (highest) current on all three legs. While the service factor is not technically there to dip into for more hp, it is there for unbalanced phase current, poor power conditioning, over/undervoltage, and so on, so if it were me, I'd dip into it and not lose sleep, especially since a jointer is not a continuous load, and will have no-load cool-down time in between cuts. A fan or pump working at capacity (max phase current on any leg) is a whole nuther thing, though, and I wouldn't be pushing it beyond the weakest link.
Tom

“This place smells like that odd combination of flop sweat, hopelessness, aaaand feet"
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#37
OK, thanks. We'll go with the 12 - 18 amp OL relay.  The capacitors just start the motor and then drop out after it hits something like 205 V, if I remember what the guy who designed it told us.  In any case, they are not part of the circuit after starting.  I'll measure the current in all three legs when we install the OL relay, but if I understand how the relay works it will trip if any of the three legs exceeds the set point.  So whether we set it as 12.2 amps or higher it should still protect the motor no matter which leg draws the most amps.  Is that right?

Thanks again for everyone's help.

FWIW, we tried to use a VFD but couldn't get it to work, despite how easy everyone shows it to be on YouTube. Some of those videos are from guys that know less than I do about them, so beware. (I know more about the HuanYang now than I ever wanted to!) The one Mike posted wasn't bad, and you might be as lucky as he was if you try that VFD. The static phase converter was plan B, but I think it will be fine as even 3.3 HP should be more than enough on a 16" jointer.

John
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#38
" if I understand how the relay works it will trip if any of the three legs exceeds the set point."  Yes but it will not be an instantaneous trip as it allows a time delay for start up and momentary over loads.     It is designed to prevent the motor from overheating from too much current in the windings over a period of time.   Roly
I don't see where this model overload has lost phase or unbalanced phase current protection so it will work the the phase converter but if you change the starting contactor/overload make sure it will work with the add a phase unit.
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#39
(06-05-2017, 02:29 PM)Roly Wrote: I don't see where this model overload has lost phase or unbalanced phase current protection so it will work the the phase converter but if you change the starting contactor/overload make sure it will work with the add a phase unit.

We're going to have to buy a new contactor, too, because the higher capacity OL relay won't fit the existing one.  Maybe I could make it fit, but I'd rather not get into that.  So how do I determine if the new contactor/OL relay will work with the static phase converter. 

John
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#40
If it were me, at this point I'd leave the OL device off. It's a motor that's operated under direct supervision, and failure to start is not going to be an issue, it's a hand-fed machine so load on the motor is controlled by the operator, and once a feel for how hard it can be pushed (with someone monitoring an ammeter while it's worked) is established, there's little chance of burning it up. It's not an industrial machine, running automatically, and un-monitored.

But that's me.
Tom

“This place smells like that odd combination of flop sweat, hopelessness, aaaand feet"
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