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dc contactor

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ILCML

Electrical
Jan 4, 2007
52

24VDC 1/2hp 60FLA Motor roughly 20s duty cycle

Having hard time finding a DC contactor(need reversing, but non will be ok for now).

If I use 2 SPDT contactors in parrallel (in order to reverse the motor), one passing the '+' and the other '-', would I be ok with a 400A NO / 200A NC inrush rating on the contacts?



 
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I think you will bw allright. It depends somewhat on the total resistance in the power supply and the wiring. If supplied from a battery and short cables, you may see a problem.

What is the off period?

DC contactors usually have a problem interrupting current - not closing. But at this low voltage, that shouldn't be a problem either.

What about using same kind of relay that is used in trucks and busses with 24 V system?

Gunnar Englund
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
 
Thanks Gunnar...I'm not familiar with the bus and truck relays....
 
Your task is right down ROBOT alley.

I would peruse the robot places.

I googled for Power H bridge, (Which provides both directions!) The first site has 160A 50V H-Bridges.

(Look at their WEB Store)

Call them or hunt around I'm sure you will find exactly what you need AND in both directions without the clack, clack, clack, smoke, hassles.

With an H_Bridge you could use a OTS bit of brains to provide soft starting too! This would prevent frequent mechanical whacks to your machinery.

There is also Solid State Relays rated in those currents. You need to pay attention to their heat sinks and they will work well too.

Keith Cress
Flamin Systems, Inc.-
 
There are a number manufacturers of heavy current low voltage contactors for light traction applications, but at 24V most AC3 rated contactors can be used at pretty much their full rating provided there is not too much inductance in the circuit. Things start getting more tricky above about 60V and from 120V upward DC contactors are both less common and more expensive.

This link is typical of the British design of high current LV contactors:

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Sometimes I only open my mouth to swap feet...
 
What is wrong with standard 24v starter solenoids?
 
Nothing. They are among the 24 V bus and truck relays.

Gunnar Englund
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
 
Is your motor a permanent magnet field motor, series wound or compound wound? What is the application?
 
permanent magnet....I think Keith found the ideal solution...Robotpower has a nice OSMC that sounds perfect.

Thank you AGAIN Keith!!

I'm surprised finding a seemingly simple solution to reversing a DC motor is such a pain....are low voltage ('high' current) DC motor systems just not that popular?
 
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