Motor Reversing Intermittent Duty DPDT Solenoid Relay

armenon said:

Mike,
I am not very sure about that & I don't think so it happens in the application. I am not trying to do the test based on the Cole Hersee contactor. The test specification itself states that it should be 90sec ON,1.5sec OFF. I am looking for the failure mode & how long the motors would last before I see any failure. It's a validation test.
Thanks.

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I need to have a conversation with whoever wrote the test spec; they obviously put no thought into this at all, or they don't have a clue about what they are doing!!!!

First, what does 1.5sec Off mean??? No fan motor I have ever seen will begin to coast to a stop in anything like 1.5sec, so in-effect, you are trying to reverse the motor while it is still spun up in the previous rotation.

This causes the motor to draw huge transient start-up currents, likely 3X what it would be if you were starting the motor from a stopped condition. This is an extremely unnatural thing to do to the motor, and likely never happens in an automotive application. In fact, I have never seen a fan motor in a car that turns both directions. I'm guessing that it would take the motor up to 20sec to coast to a stop if it had just the aerodynamic braking of the fan.

So, is this what is really intended?

Second, if the goal is to actually reverse the motor so quickly, then using dynamic braking by shorting the motor (or connecting it to a braking resistor) will stop it faster than just letting it coast to a stop under the influence of aerodynamic braking caused by air against the blades.
That should have been specified as part of the test.

So what are you trying to do to the poor motor???

MikeMl said:

I need to have a conversation with whoever wrote the test spec; they obviously put no thought into this at all, or they don't have a clue about what they are doing!!!!

First, what does 1.5sec Off mean??? No fan motor I have ever seen will begin to coast to a stop in anything like 1.5sec, so in-effect, you are trying to
reverse the motor while it is still spun up in the previous rotation.

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I agree on 1.5sec Off. I also agree on the fact that no motor would coast to a stop in 1.5sec. It takes a minimum of 10sec atleast from the fans that I have seen so far.

This causes the motor to draw huge transient start-up currents, likely 3X what it would be if you were starting the motor from a stopped condition. This is an extremely unnatural thing to do to the motor, and likely never happens in an automotive application. In fact, I have never seen a fan motor in a car that turns both directions. I'm guessing that it would take the motor up to 20sec to coast to a stop if it had just the aerodynamic braking of the fan.

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I too don't think it happens in an automotive application. This fan is for an ATV. There are fans that operate in both directions (usually during high speeds & during idling). It depends on the vehicle condition.

So, is this what is really intended?

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The fan is for an ATV. I am trying to validate fan by doing this test. As I have mentioned earlier, I am trying to see what the failure mode will be & how long the motor would last. It need not happen in an ATV but then we are studying the worst case scenario.

Second, if the goal is to actually reverse the motor so quickly, then using dynamic braking by shorting the motor (or connecting it to a braking resistor) will stop it faster than just letting it coast to a stop under the influence of aerodynamic braking caused by air against the blades.
That should have been specified as part of the test.

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These tests are a part of the validation tests.

So what are you trying to do to the poor motor???

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I am trying to kill the motor, in short looking at its life span.

MikeMl said:

Yes. Look at the Green trace in this image:

That is the voltage applied to the motor terminals.

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Mike,

I am going to run 8 fans at a time. Each fan draws about 7-8amps. Do you think I can still run the test set up with all the fans? Would there be any damage to the diode (1N4001)?

armenon said:

Mike,

I am going to run 8 fans at a time. Each fan draws about 7-8amps. Do you think I can still run the test set up with all the fans? Would there be any damage to the diode (1N4001)?

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Since the motor current doesn't go through any of the diodes, no.

The two motor relays (U4 and U5)will have to be large contactors like the ones Kinarfi showed in his pictures. Look for regular 12Vdc Contactors;not Starter Relays.

MikeMl said:

Since the motor current doesn't go through any of the diodes, no.

The two motor relays (U4 and U5)will have to be large contactors like the ones Kinarfi showed in his pictures. Look for regular 12Vdc Contactors;not Starter Relays.

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Thanks. I will look into it.

I check my solenoid, won't work, gets hot.
https://www.digikey.com/product-sea...=0&page=1&quantity=0&ptm=0&fid=0&pageSize=500
check these out, 70 Amp 12 v 125 ma coil
You are going to need 4 of them because they don't have SPDT, just SPST.
I added a drawing based on Mike's Toggle1.asc and put diodes across all coils + a bridge diode set on the fan, it may be advisable that each fan have a set of bridge on it's terminal, Mike Please Comment.
Kinarfi

Starter relays or solenoids here in the uk are not meant for continuous operation, you might burn out the coil.

Might be worth talking to a mobile plant service centre or a motability centre, large 100s or more amp contactors are used in mobile handling equipment, not so much these days due to igbt's and fets but they are still around.

If having 2 relays or more on accidently would cause a short then electrically interlock the relays coils using spare contacts making it impossible.

not so much these days due to igbt's and fets

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Why are you insistent on using relays rather than these?

alec_t said:

Why are you insistent on using relays rather than these?

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Alec,
I am not familiar with igbt & fet. I have these relays and I thought it would be easier to have a test set up with only relays.

dr pepper said:

Starter relays or solenoids here in the uk are not meant for continuous operation, you might burn out the coil.

Might be worth talking to a mobile plant service centre or a motability centre, large 100s or more amp contactors are used in mobile handling equipment, not so much these days due to igbt's and fets but they are still around.

If having 2 relays or more on accidently would cause a short then electrically interlock the relays coils using spare contacts making it impossible.

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dr pepper,
Thanks for the information. It's been tough working on this.

kinarfi said:

I check my solenoid, won't work, gets hot.
https://www.digikey.com/product-sea...=0&page=1&quantity=0&ptm=0&fid=0&pageSize=500
check these out, 70 Amp 12 v 125 ma coil
You are going to need 4 of them because they don't have SPDT, just SPST.
I added a drawing based on Mike's Toggle1.asc and put diodes across all coils + a bridge diode set on the fan, it may be advisable that each fan have a set of bridge on it's terminal, Mike Please Comment.
Kinarfi

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Kinarfi,
Right now I'm working on Mike's circuit. I'm going to test it with 1 fan & see if it works. It works in the software. I'll update once I test run the 1st fan.
Thanks.

MikeMl said:

Since the motor current doesn't go through any of the diodes, no.

The two motor relays (U4 and U5)will have to be large contactors like the ones Kinarfi showed in his pictures. Look for regular 12Vdc Contactors;not Starter Relays.

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Mike,
I have the test set up per the circuit diagram. The fan runs in only one direction though.
Secondly are the diodes arranged correctly (I mean the current flow direction)?
Thanks.

I started late on in the threads, is the schematic a relay flip flop?

The 2 relays with 6v coils might be the issue.

I've used a 2 relay flip flop circuit a couple of times on some old equipment we have.

dr pepper said:

I started late on in the threads, is the schematic a relay flip flop?

The 2 relays with 6v coils might be the issue.

I've used a 2 relay flip flop circuit a couple of times on some old equipment we have.

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I believe so. Does it contradict your flip flop circuit?

Nope there are many ways of doing it, the number of relays in your circuit is probably the minimum you need.

dr pepper said:

Nope there are many ways of doing it, the number of relays in your circuit is probably the minimum you need.

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A schematic of flip flop.

Have a look at this:

https://www.emil.matei.ro/onof2.php


I think your issue is possibly a mistaken connection, however if you read the blurb you can see that this and your design rely on one thing about the relay, that the holding current is much less than the pull in current, I suspect that if there are no errors with your circuit this might be along the lines of why it isnt working (not wanting to poop on anyone), the design of the relay plays an important part.
Double and triple check your connections before you condemn your circuit, might be worth building just the push on/push off circuit and see if that works on its own.

dr pepper said:

Have a look at this:

https://www.emil.matei.ro/onof2.php


I think your issue is possibly a mistaken connection, however if you read the blurb you can see that this and your design rely on one thing about the relay, that the holding current is much less than the pull in current, I suspect that if there are no errors with your circuit this might be along the lines of why it isnt working (not wanting to poop on anyone), the design of the relay plays an important part.
Double and triple check your connections before you condemn your circuit, might be worth building just the push on/push off circuit and see if that works on its own.

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That is the reference I linked to way back in post 15 of this thread.

That is also the basis of the toggle part of the .asc files I posted earlier. It simulates just fine with relays that have a hold-in current of ~1/3 of its pull-in current.

Oops, sorry I've not been keeping up.

I built the flip flop earlier to day and it worked just dandy, definitely going in my neat diagrams folder.
Kinarfi