24" Planer failing to start on 20 HP RPC

[biocmp]

Hi all, I have some German woodworking machines that I run on an RPC with stepup transformer (purchased as a bulk package). The planer will (sometimes ~ 50%) fail to get to full speed before aborting it's start-up, as if it's not able to get enough power. It'll start it's spin-up process and at about 3-4 seconds, something trips/triggers and begins the deceleration process. I will often have the 5 hp dust collector already running, it's also a 480v 3ph machine that shares power.

The Phase Converter is a Phoenix Phase Converter (CNC grade):
20 HP
45 continuous amps
65 max amps

The phase converter is on a 60 amp breaker.

The planer has these numbers listed:
480v
20A
7.5kw

The 3 phase load center that pairs up with the RPC:


Here's the step up transformer:



I'm considering stepping up to a Phase Perfect or bigger system. I'm an absolute rookie when it comes to electrical, I'm in the process of reading/watching vids to better understand but wanted to get this thread started to see if some of you'd be willing to help speed up my learning process.

 

[dalmatiangirl61]

Is the breaker tripping? I think the breaker may be too small, and what size wiring feeds the rpc? The planer will pull 2x to 3x nameplate amperage on start-up, does the mfr of the rpc have installation recommendations? For reference my 20hp rpc is on a 125A breaker, as per mfr recommendation.

Edit: Looking at mfr website they recommend 100A max breaker, and #4 wire for single phase feeding rpc.

 

[biocmp]

It's not tripping because if I go and turn off the dust collector and give it a bit of time, I can get the planer to start up without issue. Then I can fire up the DC again. I'll report back with the set-up numbers.

 

[johansen]

Sounds like a auto reset circuit breaker on the start capacitors of the rpc. With a heavy load like you describe they may re-engage.

You need to figure this out before you burn something up.

Or the overload trips and by "starts the decelleration process" you mean the rpc shuts off completely drawing no current and it coasts to a stop.

 

[JST]

Planers tend to have a lot of inertia, which is why it is still not started all the way after 3 or 4 seconds.

I am not clear on what is tripping that "starts the deceleration process". Apparently something that self-resets, since it starts without you having to reset anything.

It may be that your step-up transformer is not able to hold the 480V, so the motor takes a long time to start on the reduced voltage. Then, a thermal in the motor may cause the planer to drop the contactor out and stop the machine.

If it happens more often when restarted after running for some time, I'd be even more inclined to think that is the issue, because the motor is already hot, and a slow start may heat it even more.

Check the voltage coming out of the transformer, and the voltage going into it. If they drop about the same percentage, the issue may be in the converter, or even the electrical service. Voltage checks on the input of the converter would help figure it out in that case.

The motor may take more than 3x, as much as 5x the full load current when starting. The overload system will tolerate that for a while, but not necessarily for a slow start.

I;ve had motors refuse to come up to speed due to low voltage, and they can pull a lot of current, but at a low voltage. The current is drawn down by the high current, which slows the motor and draws more current. It ends by tripping an overload.

 

[MwTech Inc]

I was typing the same answer as JST just wrote.....lol
Some part or multiple parts of your "power System " are under sized to carry the startup time of the planer.
Under voltage to the planer will worsen the issue.
I would not continue operating stuff until its resolved.

 

[biocmp]

Thanks guys, I'll start acquiring some gear to get readings so I can step through this. Again, this is a relatively new world for me so I'm going to take slow, deliberate steps through this.

Are we saying the 60 amp breaker supplying the RPC is no longer a suspect? I was thinking the 60 amp single phase wasn't enough to fully feed the 60 amp 3 phase and so if the start-up pulls 3-5 times rated draw, there could be a protection mechanism built into the motor that trips when enough current isn't detected. That's why it isn't tripping at the breaker(s).

Or perhaps that's exactly what you're saying above? With the additional caveat that it could also be a voltage issue?

 

[MwTech Inc]

All motors draw 3/5 times the rated amp rating at startup, your fridge at home does the same thing.
However, it is for a very short time, maybe like 1/2 second??(+/-)
Provided everything from the breaker panel to the planer is sized correctly , the system can absorb this spike and all is good.
Now in the case of your planer, it takes more "time" to spin that 24" head up to speed....that is your problem.
What you have now can't handle the start-up load.
It could be the wire size is not correct, loose connections causing increased resistance, mechanical issue with planer(tight bearings) bad contactor in the planer control panel that is has burnt contacts....\etc.
Improper wire size will cause high amps and a drop in voltage to the motor which is not good. Wire size also is dependent on length but I'm assuming (?) the breaker panel, converter, machines are rather close to each other??
Once you have a meter you need to measure your actual incoming power.
Alos need to check your transformer and make sure it tapped correctly that someone didn't change things trying to modify the output voltage.
Just measure the output voltage going to the planer, should be within 10% of the 480 plus or minus.
Now if you are new to electric, 480 can kill your butt, period,
480 has potential, meaning it will "jump/arc" to something close to it, so if you are holding your test leads on the terminals and you let your finger wander to close
well, you will get hit. If you are not comfortable with this you may consider hiring an electrician that works with industrial equipment (not a residential guy) to overview your system. An hour of his time may be well worth it.

 

[biocmp]

I appreciate the warning MwTech.

While I wait for my multimeter to be delivered, I went and grabbed what info I could:

• 6 AWG Panel to RPC - 60 amp Breaker
• 6 AWG RPC To 3ph Subpanel
• 6 AWG 3ph SubP to Transformer
• 4/cC12AWG 600v FT2 transformer to machines

RPC box

20 HP motor generating 3rd leg:

3ph subpanel:


Transformer showing connection to 3rd tap on each:

Transformer front plate diagram:


And WTF, I have no idea but this is where my planer decides how to do stuff with the power that is fed in:

 

[JST]

I spotted K1T which seems to have either a 5s or 6s setting for "time". That probably explains the cutoff of power.

Probably good, you do not want to "let out magic smoke".

Out of curiosity, do you have anything else run by the RPC?

I ask because sometimes it is possible to start a tough load by running another 3 phase motor at no load. That forms an "auxiliary idler", and boosts the "manufactured leg" current capacity.

If you did try that, and it worked, it would indicate that the deficiency is in the RPC capacity. You could continue to use the "auxiliary idler" to start the planer, and likely plan to upgrade the RPC at a later date.

This seems possible because the weakest link in the system is usually the ability of the RPC to generate the third (manufactured) leg of the 3 phase. if that is too weak, the necessary torque to accelerate tough loads may not be present.

You can also find this out once you have a meter with which you can check the voltages at the 240V output of the RPC, before the transformer.

 

[stoneaxe]

Find a local industrial electrician. Bite the cost, and do it.
Smoking the electrical's is expensive, smoking yourself even worse.
Trust me, I have done all three.

 

[biocmp]

I spotted K1T which seems to have either a 5s or 6s setting for "time". That probably explains the cutoff of power.

Probably good, you do not want to "let out magic smoke".

Out of curiosity, do you have anything else run by the RPC?

I ask because sometimes it is possible to start a tough load by running another 3 phase motor at no load. That forms an "auxiliary idler", and boosts the "manufactured leg" current capacity.

If you did try that, and it worked, it would indicate that the deficiency is in the RPC capacity. You could continue to use the "auxiliary idler" to start the planer, and likely plan to upgrade the RPC at a later date.

This seems possible because the weakest link in the system is usually the ability of the RPC to generate the third (manufactured) leg of the 3 phase. if that is too weak, the necessary torque to accelerate tough loads may not be present.

You can also find this out once you have a meter with which you can check the voltages at the 240V output of the RPC, before the transformer.

The other things hooked up are a dust collector, which is usually running before the planer is turned on and the jointer and a bandsaw. The jointer and bandsaw aren't run concurrently with the planer.

 

[dalmatiangirl61]

Are we saying the 60 amp breaker supplying the RPC is no longer a suspect? I was thinking the 60 amp single phase wasn't enough to fully feed the 60 amp 3 phase and so if the start-up pulls 3-5 times rated draw, there could be a protection mechanism built into the motor that trips when enough current isn't detected. That's why it isn't tripping at the breaker(s).

If the breaker is not tripping, it may not be the problem, yet,,,,, the #6 wire feeding rpc is undersized according to mfr, I'm not sure about wire size to panel. I'm not an electrical engineer, so I try to follow mfr recommendations, so if there is a problem I know breaker/wire size is not the problem, otherwise its a nagging question mark in my brain.

Electrical codes for phase converters https://up.codes/s/phase-converters

 

[JST]

The other things hooked up are a dust collector, which is usually running before the planer is turned on and the jointer and a bandsaw. The jointer and bandsaw aren't run concurrently with the planer.

The dust collector is no help, it's a "load" all the time. The jointer or bandsaw may help, depending on motor size.

 

[biocmp]

The dust collector is no help, it's a "load" all the time. The jointer or bandsaw may help, depending on motor size.

Thanks, the jointer is a 5hp, the bandsaw is...I think a 3hp. I'll grab that info later.

 

[M. Moore]

I see a 400 to 230 volt transformer in the planer electrical box. Did you check that the planer motor is actually 480 volt? Often Euro motors are 380 volts. Germans don’t usually make this kind of mistake electrically as you can probably tell from the extremely well ordered wiring in the box.
Also what starts your rpc? There is no start contactor with appropriate overload safety heaters in the box. Are you turning on the breaker each time to turn on the rpc?

The safety switch you are calling a load center is just a safety disconnect, not a load center. It does have fuses so it is appropriate to have it in between the transformer and planer however the fuses are too large to provide any protection. I am wondering about your other machines? Are they 240 volt or 480 and how are you getting power to those machines?
Ideally you would run the rpc output into a proper 3 phase load center sub panel with enough breaker space to run all your 3ph machines. Then each machine will have its own breaker just like your single phase panel. If the machine is a long way from your sub panel then you will need a safety disconnect (not necessarily fused) to isolate the machine at or near the machine.

You most definitely need a proper industrial electrician who knows how to wire 3ph machines. The situation you have there is dangerous.
The planer trying to start and dropping out is a huge red flag and you don’t even own an electrical meter.
Your entire system needs testing BEFORE you supply power to any machine.

Good luck,