4QD 50 amp controller wanted !

[cbrew]

One thing that I have experienced first hand that is a major problem when you run multiple controllers to axle hung motors is a motor failure situation. If you have one large controller feeding 4 motors and one does fail, you are unlikely to cook the other motors as the combined output of the controller will be split between the other three motors and not overload them. Now if you have 2 controllers feeding 4 motors, and one motor fails it WILL cook the other motor almost instantly, as it is sending double the amperage to one motor now. If you have 4 controllers feeding 4 motors then you should be ok, unless they are linked and shut down when one fails. I have experienced all of these situations over the years, and I have found that the simplest setup for troubleshooting, wiring, control and failures is one large controller like a 4QD-300, Sevcon, or Navitas controller.

as long as the motors are running in parallel, you will not cook the second motor in a one controller to two motor configuration as you describe.
the extra load may cause it to cook. but just simply losing one of the motors. (the impedance of the motor will not allow it any more current to flow at the same voltage)
if you are watching the current draw into each controller, you will see the current draw drop by~half when the motor circuits open up.
in fact you may even see current loads spike and the winding over heat and begin to short out and sending the controller into a fault state. (and from what i have researched, this is a killer for the 4qd controllers)
what you say will logically happen in a one controller to X motor configuration.. and we know it will not. again load may, not over current from losing a motor

now, if i am wrong, please show me with the numbers where i am wrong.

[fly5150]

Your numbers are correct in theory, but what happens in use is slightly different. I have spent many hours starting at different meters monitoring every different way and every different value possible. the motors can only use so much power based on the windings, yes, but they will take a much larger spike of power in short bursts. for example the motors we use will only pull 10-15 amps each at full 24vdc at a constant speed under load. But when starting, with a load at low RPM I can see a draw of 40-50 amps per motor. Now if one motor looses a pinion, or fails, yes in theory the current draw will be less, but not what I have experienced. I have burned up plenty of motors and controllers trying everything under the sun.

One thing that I have experienced first hand that is a major problem when you run multiple controllers to axle hung motors is a motor failure situation. If you have one large controller feeding 4 motors and one does fail, you are unlikely to cook the other motors as the combined output of the controller will be split between the other three motors and not overload them. Now if you have 2 controllers feeding 4 motors, and one motor fails it WILL cook the other motor almost instantly, as it is sending double the amperage to one motor now. If you have 4 controllers feeding 4 motors then you should be ok, unless they are linked and shut down when one fails. I have experienced all of these situations over the years, and I have found that the simplest setup for troubleshooting, wiring, control and failures is one large controller like a 4QD-300, Sevcon, or Navitas controller.

as long as the motors are running in parallel, you will not cook the second motor in a one controller to two motor configuration as you describe.
the extra load may cause it to cook. but just simply losing one of the motors. (the impedance of the motor will not allow it any more current to flow at the same voltage)
if you are watching the current draw into each controller, you will see the current draw drop by~half when the motor circuits open up.
in fact you may even see current loads spike and the winding over heat and begin to short out and sending the controller into a fault state. (and from what i have researched, this is a killer for the 4qd controllers)
what you say will logically happen in a one controller to X motor configuration.. and we know it will not. again load may, not over current from losing a motor

now, if i am wrong, please show me with the numbers where i am wrong.

[cbrew]

Your numbers are correct in theory, but what happens in use is slightly different. I have spent many hours starting at different meters monitoring every different way and every different value possible. the motors can only use so much power based on the windings, yes, but they will take a much larger spike of power in short bursts. for example the motors we use will only pull 10-15 amps each at full 24vdc at a constant speed under load. But when starting, with a load at low RPM I can see a draw of 40-50 amps per motor. Now if one motor looses a pinion, or fails, yes in theory the current draw will be less, but not what I have experienced. I have burned up plenty of motors and controllers trying everything under the sun.

I believe what you are seeing is called the motor's transient impedance/reactance this is why i will also suggest gearing the loco to run wide open at tracks speed limit.

it is my humble opinion what you are seeing is like a team of four works with one of them being lazy and sitting down on the job.
the same amount of work needs to be done, but with one not keeping up or out right quitting the other three have to pick up the slack. and this will translate to higher line voltage, in turn higher current being absorbed by the remaining motors, and if that load is outside the normal parameters of the motors, they will work them selves into a spot on the scrap pile.

this is also why i suggest running the largest motor one can find/fit

I hope that makes sense,

[fly5150]

Exactly!
Unfortunately for us there is not a lot of room under the frame to stuff a large motor, and so the struggle continues.

Your numbers are correct in theory, but what happens in use is slightly different. I have spent many hours starting at different meters monitoring every different way and every different value possible. the motors can only use so much power based on the windings, yes, but they will take a much larger spike of power in short bursts. for example the motors we use will only pull 10-15 amps each at full 24vdc at a constant speed under load. But when starting, with a load at low RPM I can see a draw of 40-50 amps per motor. Now if one motor looses a pinion, or fails, yes in theory the current draw will be less, but not what I have experienced. I have burned up plenty of motors and controllers trying everything under the sun.

I believe what you are seeing is called the motor's transient impedance/reactance this is why i will also suggest gearing the loco to run wide open at tracks speed limit.

it is my humble opinion what you are seeing is like a team of four works with one of them being lazy and sitting down on the job.
the same amount of work needs to be done, but with one not keeping up or out right quitting the other three have to pick up the slack. and this will translate to higher line voltage, in turn higher current being absorbed by the remaining motors, and if that load is outside the normal parameters of the motors, they will work them selves into a spot on the scrap pile.

this is also why i suggest running the largest motor one can find/fit

I hope that makes sense,

[cbrew]

Exactly!
Unfortunately for us there is not a lot of room under the frame to stuff a large motor, and so the struggle continues.

probably the next thing to focus on would be forced air cooling.

but then again, at 50 bucks a motor. if you let the magic smoke out, its not that hard of a hit.

boiling water is much easier to deal with

[Fender]

When I built my electric loco with a no-name, no-spec (400 watt??) permanent magnet 24v DC motor, using a Curtis 1505 speed controller, it wasn't long before I realized that both the motor and controller were undersized for what I was asking them to do. The motor tended to overheat, and current draw often exceeded the 20-amp continuous rating of the controller. So I put a cooling fan on the motor, a heat sink on the controller, and hoped for the best, with plans to replace both components when they burned out.
Been running several years now, and still waiting.....

[GooseOrBust]

I wish I could speak with authority, but I'm pretty good at my day job and weak on the EE topic.

I configured 2 24v motors in parallel and wired them to my 4QD controller.

While running the first time at the track, I noticed one motor getting hot. It also made an unusual noise and was loosing power.

Turns out, one of the magnets came loose! (Only MY luck, none of you have to worry). The motor eventually failed.

No other damage. I wired the setup as 4QD instructed and guess what?

The 30a fuse blew!