I have a Budgit 3 phase hoist and need to add a jog feature. The way this operates now is the up or down button closes a contactor and a solonoid to release the brake. As you can see in the attached schematic there is a reversing contactor depending on which way you are moving. I have used a hoist at work which had this jog feature which would rapidly actuate the contactor and brake (you could hear it clicking). I timed myself on how fast I could push and release the timer on my phone which is ~500ms. So maybe 200ms cycle time on a control relay. Would I want solid state relays and MOVs on the contactors and maybe there are such relays with a timer feature hmmm. Anyway I'd like your thoughts on this

 

How exactly do you want the jog feature to work?

 

What is different in the functioning of the hoist in the drawing from the hoist that you have? That is how hoists are supposed to work. Hold the button and it moves, release the button and it stops. Or does your hoist at home function in a different manner?
Please explain the difference between what you have and what you want.

 

My understanding is that the TS wants an option for the motor to be pulsed on for 200 mS when the button is pressed. (This may be two extra buttons or a swtch to change the mode of operation of the existing buttons.) A 555 timer could do the timing but if changing to solid state relays (5 or 6 SSRs would be required depending how the logic was done.) I think I would use a microcontroller to generate the 200 mS pulse and to select which SSRs were triggered for each direction. I don't think these cheap hoists would last very long if this mode was used a lot.

Les.

 

Certainly rapid cycling would be quite hard on the system, both motor and brake. If the intention is to have an effectively lower speed then how about an option to switch the feed to a variable frequency drive? Some applications even have a second motor available that drives through a speed reducer to give a much lower speed, since the slower drive has big reduction ratio. Of course it is much more complex but very precise capabilities. In fact, how about just having a variable speed drive and powering the contactor separately? In fact, a soft-start drive might be a better choice yet, but separate power for the brake and contactor would be needed. That would be the very best choice.

 

3 Phase contactors are not very fast devices, the typical rating drop out pick up time for DIN style can bee seen in the Group Schneider table.
Then there is the brake time, if fitted


In Ms
8502SA - pick-up = 9.0 to 23.0 dropout = 5.3 to 15.9
8502SB - pick-up = 8.4 to 20.1 dropout = 2.4 to 15.9
8502SC - pick-up = 8.4 to 20.1 dropout = 2.4 to 15.9
8502SD - pick-up = 14.6 to 27.6 dropout = 16.3 to 22.8
8502SE - pick-up = 17.3 to 32.3 dropout = 9.6 to 18.7
8502SF - pick-up = 13.0 to 43.9 dropout = 11.2 to 21.7
8502SG - (Series A) pick-up = 23.5 to 68.0 dropout = 13.9 to 17.0
8502SG - (Series B) pick-up = 40.0 to 60.0 dropout = 50.0 to 75.0
8502SH - pick-up = 57.0 to 74.0 dropout = 28.3 to 31.8
8502SJ - pick-up = 43.8 nominal dropout = 54.3 nominal

The pick-up or closing time is measured from the moment the coil supply is switched on to initial contact of the main poles. The dropout or opening time is measured from the moment coil supply is switched off to the moment the main poles separate.
Any coil suppression used such as BEMF diode or R/C snubber increases this time.
Also hard on the contacts if quench time is of any length.
Max.

 

The response times that Max lists are why pulsing mechanical contactors won't work. So using a jogging motor now seems even more like a great idea. A DC motor with a worm gear reduction, engaged through an electric clutch with the brake released, would allow speeds approaching zero, which ought to be good for any desired degree of slow motion for any application. Because of the additional reduction, say 20:1, The DC motor could be much smaller, and the speed control could be very simple and cheap. Mechanical complexity would be the tradeoff.

 

My chain hoist moves at 3.2 in/sec which is way too fast if you are trying to install an engine in a car. This is my hobby so I am trying to make do with what I have and I enjoy a challenge.
Max list seems to show worst case of ~120ms contact movement and if you double that for both directions 240ms seems reasonable. I can somewhat jog this by rapidly pushing the up or down button but not consistently. Another problem is the hoist starts rocking back and forth if the jog frequency is wrong. So this variable frequency drive may be worth looking into, the motor is a 1/4 Hp if I could just slow the motor down...

 

A variation on the total SSR solution would be to retain the contactors for phase sequence reversal but have two SSRs in series with two phases. For jog mode the the selected contactor for the requred direction would be energised, after a short delay (Say 200 mS) the two SSRs would be energised for the the required jog time, after another short delay the contactor would be de-energised. A microcontroller would be the simplest way to do the sequencing.

Les.

 

One interesting possibility would be to have a separate button to simply release the brake but not start the motor. it would only be useful in the lowering mode, but it seems like it could be simple enough to try. I am guessing that the hoist would start moving as soon as the brake was released if it had an engine load. Once again, understanding the application certainly helps point the suggestions in a more useful direction.

From the circuit drawing it looks like a separate DC supply with a single diode for isolation could release the brake, and with that supply off there would be no change in the hoist function. The advantage is it would be simple and cheap. At least worth considering.

 

One other alternative is to use a VFD to control the motor, run what speed you like.
Would also get rid of the contactors.
Max.

 

One other alternative is to use a VFD to control the motor, run what speed you like.
Would also get rid of the contactors.
Max.

I suggested a VS drive back in post #5, but still full voltage is needed to release the brake. And it is not clear just what that voltage is. I have seen hoist controls that did include a speed knob, for this application probably just fast and slow would be adequate.

 

If a VFD was used the brake could be fed from a separate contactor or relay switched off one of the VFD outputs such as At-Zero-Speed etc.
The coil voltage is fed in a typical manner on these types of hoist, off of a bridge in series with one of the motor phases. 230 or 460.
Max.

 

I can get a VFD for ~$130 for a 1/4 HP 3 phase and yes I would need to install the VFD after the power to the brake circuit. I found some timers (idec GT3W) which could sequence my motor-brake jog feature but they would cost more than the VFD and may not even work. Another caveat to this endeavor is I am generating my 3 phase with a motor phase converter (for my lathe) and will the VFD work with this. After looking at Marshall Wolf automation they offer a 2 phase 240 vac to 3 phase VFD. So I could eliminate using my motor phase converter when using the hoist.
By just releasing the brake would limit my control I really do need precise up down movement.
The suggestion by Les is beyond my capabilities and there is the brake release issue.
A lot of good suggestions guys.

 

I can get a VFD for ~$130 for a 1/4 HP 3 phase and yes I would need to install the VFD after the power to the brake circuit. I found some timers (idec GT3W) which could sequence my motor-brake jog feature but they would cost more than the VFD and may not even work. Another caveat to this endeavor is I am generating my 3 phase with a motor phase converter (for my lathe) and will the VFD work with this. After looking at Marshall Wolf automation they offer a 2 phase 240 vac to 3 phase VFD. So I could eliminate using my motor phase converter when using the hoist.
By just releasing the brake would limit my control I really do need precise up down movement.
The suggestion by Les is beyond my capabilities and there is the brake release issue.
A lot of good suggestions guys.

You would need to still power the two contactors off the mains, but feed the power for the motor from that VFD. The power for the brake will need to be switched with the contactors, which adds a bit of complexity. Most VFD packages rectify the AC feed so the 2-phase powered ndrive would be great. So the system gets more complex but not bad and not terribly expensive. And it may be that yo will not need to engage the brake for everything that you are doing. That will take a bit of experimentation on your part.

 

With a VFD you do not use contactors, especially on the output side, it can be done but you have to guarantee the VFD is at zero output.
The VFD can reverse the motor.
I would power the brake from the VFD PLC output At-Zero-Speed (set by parameter) This is the way I have done it for a overhead gantry crane lift, also CNC applications.
A couple of decades ago I went to a demonstration by a VFD company that made a VFD specifically for Hoist applications and the unit could hold a load at zero lift motion by holding the load stationary while lifting.
Max.

 

This whole thread is why I prefer a chain fall for car motor changing. Would never even think of doing it with an electric lift, they move way too fast for getting things angled correctly.

 

This whole thread is why I prefer a chain fall for car motor changing. Would never even think of doing it with an electric lift, they move way too fast for getting things angled correctly.

Maybe the VFD option would give control needed.
Max.

 

Just for fun, I decided to go through the exercise of converting a fair sized paper shredder into a variable speed winch. It just took a bit of mechanical re-arranging, primarily removing all of the cutters and creating a take-up drum. It is not a terribly powerful winch, only good for about 200 pounds straight lift, but that is with the 24 volt motor running on 12 volts..With any sort of multiple pully rig it should easily handle 400 pounds, which is enough for my application. And between the gear reduction and the friction it simply stops when the power switches off.

And yes Max, it may well be better to handle the reversing from the drive, some of them do offer that option..

 

And yes Max, it may well be better to handle the reversing from the drive, some of them do offer that option..

In the 40+ years I have been using them, I have yet to come across one that did not have a reversing feature??
And this covers a whole variety of makes.
Max.