Hoist brake solenoid buzzes/fluckers instead of steadily pulling

"Michael A. Terrell" fired this volley in news:2-SdnfxviMFXnF3TnZ2dnUVZ snipped-for-privacy@earthlink.com:

You are missing a basic point. 230VAC line voltage is measured RMS (root- mean-square) it's peak is 230*sqrt(2). I said, "the voltage will never rise above peak".

Lloyd

Ignoramus22978 fired this volley in news:TcednaUF1axtn13TnZ2dnUVZ snipped-for-privacy@giganews.com:

Ig, there is a case where a diode might be used, but you'd see it, and a switch to cut it in and out of circuit, if it were there.

The case is where a coil is wound "strong" for pull-in, then a diode is placed in series to lower the coil's average current during the hold phase.

However, that would be obvious, and external to the coil.

LLoyd

I've also worked on solenoids like that that have a switch and a resistor for the "hold" circuit. Follow the wires. Same thing, if the resistor or that circuit is open the solenoid will chatter open and closed.

This is assuming the solenoid does chatter, as if it's being turned on and off rapidly, like a machine gun.

If it's just hanging up part way and buzzing then I'd agree with the people who said to clean it up or replace it.

It's nice that you are attempting to help others, very admiral of you how ever, this person you are replying to has been on my ignore list for some time now and for good reason. You may also learn why if you haven't already.

I also write software at times and posted a question about options that may exist in the "NNTP" protocol, which is used here, to exclude down loading from the server if I happen to have a exclusion of a user in the header of the post. It gets messy trying to ignore these characters even though you have your own reader configured to do so, how ever, reading others post ends up showing you users that you don't want any thing to do with.

I just though it would save lots of bandwidth for others to use and enjoy.

I guess it's just a weakness in the protocol.

Jamie

Jamie fired this volley in news:WVTvq.35422$ snipped-for-privacy@newsfe01.iad:

Jamie, he was correct, except for forgetting that AC line voltage is the root mean square of it's peak. A lot of people forget that.

I'm an old radio guy from the 60's, too. That was long before the advent of switching power supplies. To get 5VDC at 1A off the mains used to take a 1lb transformer, and about 40 cu.in. of rectifiers and filters -- and regulation sucked unless you really over-sized the transformer.

Now you can get that out of a 1/2-oz wall wart!

LLoyd

The point is that he goes out of his way making an idiot of himself, he can't even get my identity correct. I am not the only user with this name.

I deal with this crap at work all the time when the electricians walk over to me with unexplained problems, some of which are hoist how ever, we deal with much larger cranes than what is being talked about here.

We just recently had a 10 ton crane inspected after a repair done on the motor brake which is much different than what is being talked about here. That one uses a DC coil with a bridge rectifier and this bridge is actually encased in the coil pack. This coil can operate from AC or DC how ever, the way this one is being operated is it first gets energized via 48V AC, then a time delay relay opens its contacts to operate a single diode inline which allows for 50% duty to the coil for holding.. It is a Peak and hold motor brake and works very well. We had to replace it not to long ago because the contacts in the control box got welded and what happens is with a lot of constant use the coil heats up the spline and starts to stick and thus does not always close afterwards. You can picture what happens to the load when the operator releases the buttons.

Personally I stay clear of MT. He is a force to be reckon with. Also I never made any comment on his evaluation of the math or what ever he spit out, I just don't bother reading his crap because it normally has nothing to do with helping any one. I only see him from other users posting replies.

Jamie

Maynard A Philbrook JR is the only one with the callsign KA1LPA.

This is exactly what it does.

No, it chatters like a machine gun.

The hoist can be entirely rewired for 240/480. It actually WAS wired for 480 and I had to rewire. So, you are saying that to complete this transition to 240, I would have to replace the solenoid?

Ok, let's back up a bit. WHEN was the last time the hoist worked like it should? When it was installed and operating on 480 v?

Or was it working at some point when re-wired for 240 v and THEN started to act up with the brake solenoid?

Jeff

That would be a "Pick and Hold" solenoid. The "Pick" is the strong winding with the switch, and the Hold would be the weak constant winding.

And the Pick might not be able to pick without the Hold being energized too, so it buzzes and doesn't open all the way. Or it's bouncing on the end switch - hard to tell without looking.

Check the connections - If it's two separate windings, there might be a loose lead.

-->--

Yup, it's just a standard box solenoid, probably Dormeyer they make zillions of them - and all crapped up inside that end-bell. If it was something fancy it would look it.

Take it apart and clean up all the sliding and metal surfaces, a little dab of Lubriplate white grease on the moving pole pieces inside the solenoid, and hit it with some clear-coat to stop the surface rust on the metal parts - and stop leaving it outside in the rain.

You do NOT want to pull an "Honest Al Babin" and start painting all over the insides. You want to see if something is starting to crack.

-->--

I bought it at auction.

I have never seen this hoist run.

At my place, I have 240v 3ph only. (well, I have a transformer that I could wire to get 460v, but it is sitting in the corner right now).

Well, what I know is that I did measure voltage at the solenoid terminals, and it was 230v.

Follow the solenoid wires to look for an end of stroke switch. If it has one it will be actuated and open when the solenoid is pulled in. Check that circuit for a resistor or something else to lower the solenoid voltage. The problem is that it gets power on the pull stroke but no power for the hold position.

That amount of surface rust and corrosion INSIDE a cover indicates it's been wet, or in a wet location.

That's a disc brake and should dis-engage when the hoist is in operation.

Do you have the wiring diagram for this hoist?

I know that label reads, "Caution dual voltage" as an indication it "might be wired for a different voltage than what you're using.

Despite all the random guessing, I'm assuming that is a very simple straight forward coil that pulls the release on the disc brake.

If that coil is set up for 480 volts and you're putting 240 across it, it IS going to buzz and chatter. It will do that without any missing diodes, open coils, hidden switches or two sets pull & hold windings.

If that coil is set up for "dual voltage" it should have more that two wires connecting to it. Or there should be a control transformer somewhere else in the housing to supply the correct voltage to a single voltage coil. Or a dropping resistor (not likely) to allow a 240 coil to be used on 480. And the instructions, as such, should have the connection for both voltages and everything you have to reconnect listed.

Jeff

If that being the case, I then would assume that maybe the solenoid was getting its voltage from one of the star windings on the motor?

A connection from wire 4 to wire 5 should provide ~ 230V Ac when the motor is wired for 480 which is a standard way of doing it, how ever, I wonder if you considered this when you did your change over?

Of course, I don't know anything about anything so don't listen to me.

Jamie

Ok, so what is the original coil voltage suppose to be? 230 or 480?

You do know that many of those types of devices that allow you to rewire uses the same coil for both voltages? Normally the coil is spec'd out for 230V AC.. which will work in either case, it's just where you connect the wires to.

Jamie

Has the OP ever said if there are two or three or how many wires going to the solenoid????