DC contactor/starter circa 1900 needs replacement

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darekelec

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nyc
Good afternoon.
I would like to replace a really old contactor for a 10hp, 230 VDC motor. It comes from early XXth century. It starts and accelerates the motor in 4 stages (increments) every 5 seconds (more or less) and then keeps it running till a water tower tank is full.
The contactor is a part of a setup to provide water to a water tank on top of a high-rise building.
It's coil is 230 VDC. It has to start and run as long as it receives voltage.
Is there a replacement unit on a market or would I have to build it from parts?
Would it be destructive for the motor if I didn't start it in 4 stages (increments) but used a simple 2 pole contactor? Is there a contactor with a DC coil?
Whats the science behind starting a DC motor like this?

I prepared a dropbox folder with a couple of pics and a short video.

https://www.dropbox.com/sh/cghqzf01ah0pmkd/AABWIhQcc3GPWbjmemgGdJREa?dl=0

Actual replacement part(s) would be very appreciated.

Thank you.
 
Is this a positive displacement pump or a centrifugal or impeller pump? That makes a big difference on the torque load on the motor during startup.

BTW, how did the contactor deliver stepped voltage? A very big series resistance bank?
 
GoldDigger said:
Is this a positive displacement pump or a centrifugal or impeller pump? That makes a big difference on the torque load on the motor during startup.

BTW, how did the contactor deliver stepped voltage? A very big series resistance bank?
Click to expand...


I don't know the term and I don't have experience with motors. Factories moved to China so we do a lot of residential here.
I think there is a big resistor (bank) behind the black board. It looks like a portable oil filled heater.

My intension was to find a relay that would close 4 contacts in 5 second increments and connect 4 contactors to it.
Changing motor or adding VFD are too much for me and the client. Pump #2 is a backup and its contactor needs replacement. It is a working system so client won't invest a lot of money.
 
GoldDigger said:
Is this a positive displacement pump or a centrifugal or impeller pump? That makes a big difference on the torque load on the motor during startup.

BTW, how did the contactor deliver stepped voltage? A very big series resistance bank?
Click to expand...
It would normally be a set of contactors. The intermediate ones would not be very big as they only have make current and not have to rated to break it. And for 10HP starting, the resistor bank wouldn't be very large. Last one I did was in 1975, (the motor was c1935 vintage) so I'm a little hazy on the exact details but around 10HP. Yes, Imperial units from that era............:)

Somewhat irrelevant but quite an interesting project. An ancient paper making machine from a defunct paper mill in UK exported to Taiwan.
 
After playing video couple of times i realized there May be 5th stage of running the motor because it accelerates even more after the shaft of contactor reaches the top.
I'm not gonna touch this project if I don't know what I'm doing.
Still interesting to learn.
 
darekelec said:
After playing video couple of times i realized there May be 5th stage of running the motor because it accelerates even more after the shaft of contactor reaches the top.
I'm not gonna touch this project if I don't know what I'm doing.
Still interesting to learn.
Click to expand...

Wise move. What you have described is not a contactor.
 
darekelec said:
I don't know the term and I don't have experience with motors.
Click to expand...

darekelec said:
I'm not gonna touch this project if I don't know what I'm doing.
Still interesting to learn.
Click to expand...

One thing that you can do is see if there is a motor repair and rebuild shop in the area. DC motors don't last forever and are so expensive they do get rebuilt. They may have a tech or engineer that can make a site visit and try to advise you on the best solution.

There are not that many DC motors around these days so it may be cheaper to discard and replace. Just ask what the rebuild cost is on the motors you have and this will give you an idea.

Even a rebuild kit for the motor starter will be expensive if you can find one.
 
growler said:
One thing that you can do is see if there is a motor repair and rebuild shop in the area. DC motors don't last forever and are so expensive they do get rebuilt. They may have a tech or engineer that can make a site visit and try to advise you on the best solution.

There are not that many DC motors around these days so it may be cheaper to discard and replace. Just ask what the rebuild cost is on the motors you have and this will give you an idea.

Even a rebuild kit for the motor starter will be expensive if you can find one.
Click to expand...
I don't greatly disagree with any of that.
My early experience on variable speed drives was dc and there are a good many still in operation. Technology has moved with the invention of SCRs and their performance improvements over several decades. And that might be the way for the OP to go rather that try to rebuild a starter.

Or just walk away as he has suggested. He? Just an assumption on my part.
 
I dont have any advice for you, just wanted to say those are neat pics and video. I've never seen anything like it; outside a museum, I doubt there's anything in the state like that, let alone still operational.

Any chance you (or someone else) can repair the 'contactor' that is bad?
 
My system will not allow connection to DropBox (security risks) so I can't see your system. It's likely from the description that what you have is what was called a "tap changer" or a "4 point starter".
20140926_152147.jpg
Those are so obsolete that I doubt there are more than a dozen people in the entire country willing to work on one. I would replace it by getting a new AC drive and motor for your pump.

If you don't want to change the motor, I would at least replace that controller with a new commercially available DC drive. DC motors are relatively simple, there is no reason a modern DC drive could not replace this. Those old controllers were special only in that back in those days, that was the only way to get variable speed. A lot of old old ski lifts and elevators were operated that way, back in the 70s I did a lot of retrofits of those old tap changers to simpler solid state (SCR based) DC drives. Easy-peasy.

Here's a video on how a 4 point starter actually works, for the curious. The motor is nothing different from any DC shunt motor.
https://www.youtube.com/watch?v=vhnbvxrAucg
 
Think of it as a Soft Start System for a modern Air Compressor. It allows the rotating equipment to slowly be brought up to speed without the high Inrush Current of a Hard Start. It probably used Whale Oil in Cylinders with graduated hole sizes in the Pistons for a Stepping Timer. Probably dates from 1900 to 1930 install. Don't know if the Soft Start was to protect the Pump, Motor, or the Power Bill.
You could replace the Timing System with a small PLC with a very simple Ladder Logic Timing scheme. For switching the DC; use DC Power Contactors instead of AC Contactors. The DC Contactors are designed to handle the 'Flash' or Counter EMF when switching from one Grid Resistor to another. It will burn the AC Contactor Tips. If you decide to tackle this, PM me and I will source the DC Power Contactors for you.

The DC Motors can be 'Basiced' about every 20 - 50 Years and could be Rewound with modern Insulation to last forever. Lots of Motor Shops out there doing DC Motors for the Rail Industry. If you did replace the DC Motor, use a Modern Soft Start system just in case it was for Pump protection.

JimO
 
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