Electrician Talk banner
1 - 20 of 28 Posts

·
Registered
Joined
·
2,657 Posts
Getting 180 HZ on a generac start up test. Anyone know where I can adjust Rpms ? Someone elses install. I was called in for start up and test
It might really be outputting 60hz fundamental but I have many times read 120 and 180 on the frequency meter because of spikes or distorted waveforms. There may or may not be a problem. Can you try a resistive load and look at the frequency again?
 

·
Registered
Joined
·
4,664 Posts
It might really be outputting 60hz but I have many times read 120 and 180 on the frequency meter because of distorted waveforms. I'm not saying that nothing is wrong though.
Good catch...maybe rechecking the frequency with a load applied might get the answer. (Use heaters or something not sensitive to frequency of course.)
 

·
Registered
Joined
·
11,762 Posts
That would mean the generator is at least running at double its design speed... overspeed should have kicked in by now.

Have you plugged in a fan (use an induction motor unit) or something to see if it really is that high?
 

·
Registered
Joined
·
4,664 Posts
Rpms sounded normal
Then you should:

We are just saying that it's unlikely that you have an overspeed problem. I would plug lights or heaters in without a second thought.
What I said above holds true, put the genny under a load and try reading frequency again. If the issue is a dirty no-load waveform you'll know right away. I feel confident that it IS a non-issue. If the rpm's sound normal and the voltage is in range then load 'er up and try again.

If you have access to a PQM or Oscilloscope you can verify both frequency and how clean or dirty the waveform is.
 

·
Registered
Joined
·
4,664 Posts
The speed of a genny does not dictate the frequency of the output !
It is the design of the alternator that dictates the frequency !

Your ammeter is reading harmonics not the fundimentals.

Bzzzztttt wrong.

It is the rpm of the prime mover divided by the number of poles in the alternator which determines the frequency. It is the number of turns per pole that determines the voltage! (Note that both factors DO interact to a degree however....overspeed or underspeed CAN affect the voltage too.)
 

·
Registered
Joined
·
4,664 Posts
#of poles and rpms dictate HZ
Ummm,,, someone already said that: :whistling2::laughing:

Bzzzztttt wrong.

It is the rpm of the prime mover divided by the number of poles in the alternator which determines the frequency. It is the number of turns per pole that determines the voltage! (Note that both factors DO interact to a degree however....overspeed or underspeed CAN affect the voltage too.)
 

·
Registered
Joined
·
4,664 Posts
Yeah read post #1 rpms
LOL you are not on your "A" game today are you? Much like SCE....:laughing:

1: You asked how to adjust RPM's;
2: In post #8 you said RPM's sounded normal;
3: Meadow, 8V71 and I have all said we feel that the problem is simply a dirty waveform caused by no load on the genny, and suggested you try measuring again with a load of heaters or lamps applied to see what you get;
4: You still haven't tried what we suggested to see if that solves the problem.

Now, don't make me have to drive down there and make you look foolish. :laughing:

If I have time I may dig out my 'scope and do a no-load test on the generator I bought for this outage to see what it reads....but I can tell you that both my fridge and the UPS for my internet stuff are running quite happily off of it. :thumbup:
 

·
Premium Member
Joined
·
7,413 Posts
Discussion Starter · #17 ·
LOL you are not on your "A" game today are you? Much like SCE....:laughing:

1: You asked how to adjust RPM's;
2: In post #8 you said RPM's sounded normal;
3: Meadow, 8V71 and I have all said we feel that the problem is simply a dirty waveform caused by no load on the genny, and suggested you try measuring again with a load of heaters or lamps applied to see what you get;
4: You still haven't tried what we suggested to see if that solves the problem.

Now, don't make me have to drive down there and make you look foolish. :laughing:

If I have time I may dig out my 'scope and do a no-load test on the generator I bought for this outage to see what it reads....but I can tell you that both my fridge and the UPS for my internet stuff are running quite happily off of it. :thumbup:
Offsite now. Have not measured this before. I would need your credit card info, before I test with a load ! Lol
 

·
Can't Remember
Joined
·
11,044 Posts
What size generac is this? Presumably liquid cooled of some size 22kw or larger.

Ok 17kw, duh in title, sorry. Air cooled? 3600 rpm. That thing would have to be really howling to get 180hz I would think. Usually you can tweak the voltage and Hz through the controller.
 
1 - 20 of 28 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top