feedback couses contactor to switch off with delay

I use a contactor to switch off the brake off an 3x380V electrical hoist.

Becouse there are only 3 phases and no control signals, I use two phases to feed the coil (380V). When the motor turns left or right, the contactor switches. So far, no problem.

When lowering the load, the moment the power is cut, the contactor closes with a delay of a few ms. This couses the load to accelerate for a moment before the brake turns on.

Is there any simple modification or sollution for this ?

Maarten.

I'm having a difficult time picturing where the relay coil is with respect to the motor and the motor's contactor.

If the relay is on the motor side of the contactor, when the contactor opens, the motor's internal emf will feed back to the relay coil until it decays. Depending on the motor characteristics and the relay's drop out current, this could hold the relay energized for many milliseconds. Does this sound like a description of the situation?

Connect a set of auxiliary contacts in the contactor to the brake control circuit such that the brake is engaged immediately upon opening the contactor.

electrical hoist.

use two phases to

the contactor

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contactor closes

accelerate for a moment

contactor

coil until

relay's drop

a

brake

upon opening

Brilliant job of sorting out the situation. with good adivce... from a virtually impossible description.

Phil Scott

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Nah. Its easy. I used to provide manufacturing support involving the deciphering of some really bizarre engineering designs made by people working in technically backward third world countries.

I used to work for Boeing.

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3x380V

signals, I

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coil

the

the

relay

the

like

?

the

immediately

involving the

by people

:) I was at Boeing Military Airplane in Wichita when they wired AirForce One..all green card guys for some reason we had never managed to fathom... they ran the avionics wiring on the same side and in the same wire ways as the high voltage for running gear. they had to rewire to get the thing off the ground.

We gave each other a hard time... this was in 1989... I told them that air bus was going to eat their lunch if they kept screwing around ... hillarious they thought..said air bus has only 5% of the market. Apparently they were unable to extrapolate a curve.

Phil Scott

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No. I've seen them draw the curve with market share crossing for a few years. Management's reaction to the Airbus threat was just to shrug.

Evidently, they figured that they'd be able to suckle at the government teat to keep that operation alive. Now look what its getting them. I'm waiting to see if they send armed FBI agents in to secure internal memos any time now.

The other Phil got out just in the nick of time and did so in a way that makes it appear he wasn't running for cover.

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when

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and

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to

good

made

they

had

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for

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bus

to

for a few

to shrug.

Thanks for the info.. In 89 it seemed they thought air bus was just a flash in the pan and that no way could the boeing jugernaught be taken from its pedidistal...

Interesting that they were plotting the intersect and not doing anything about it... except hiring morons in top management.

government

them. I'm

internal memos

France dumped microsoft because they had traced a lost Airbus contract to Boeing to espionage through microsoft back doors.. ostensibly operated by our own US intelligence agencies. In light of that, and from smoke seen on other horizons, I think we will see a lot of rug sweepin' and not any expose that goes deep.

in a way that

From what I could tell at a distance he was a complete jerk... but I dont know for absolute sure. the pic of him in the Time mag illustrated his blood pressure range I believe.

I think the larger picture is that the US govt has gone entirely corrupt at top levels along the lines that President Eisenhower warned of, and that anything connected goes corrupt by means of the stooges they put in charge of the sychophant corporations.

I was in Wichita days before a navy inspection of the A 6 (with the new composit wings)... they ran out of bolts..so installed short ones, and just glued the nuts on. An edict from above no doubt. They got caught.

I was naive in those days. The order probably came from the navy in order to keep the contract rolling and the graft on schedule.

A few days later as were all laughing about that, the evening nooz had pics of a rear passenger door falling off a 737 or whatever in flight.

Impressive.

Phil Scott

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that nature