Fisher Price Breaker Size

[Jim E]

Only 2 FP motors are allowed and they must be connected to 30A minimimum breaker per the rules. I recommend speed controllers over relays, since the relay is only rated at 20A by default.

[EricH]

Originally Posted by Jim E

Only 2 FP motors are allowed and they must be connected to 30A minimimum breaker per the rules. I recommend speed controllers over relays, since the relay is only rated at 20A by default.

I'd appreciate seeing which rules on this. I'll go with you on the speed controllers, referencing <R54-A>, but I didn't see any rules on minimum size for a breaker (other than in the wiring rules, which are wires for given sizes of breakers).

[Jim E]

I don't want to get into symantics here, but a 20A relay will burn if it is pushed beyond its limits. One stuck ball and the FP motor will push the current limits before it too burns out.With a relay, there is no stopping the destructive current and possibly both devices will be lost. A speed controller handles the current surge better and may go into protective shutdown rather than release the magic smoke.

You mentioned wire gauge, the fact that FP motors spec a certain guage makes it mandatory to use a device that can handle the current required of that guage. Sure, it may only draw 15A, but catastrophic motor failure in a stall condition may draw upwards of 50A from the FP motor. Avoiding wiring fires is always desirable. Better to plan ahead of the safety inspectors than to hope you won't be caught in violation.

[writchie]

IMHO the application rules are R46A and R54A.

You have to connect the FP motors to a Jaguar or Victor. A relay is not allowed.

You can supply the speed controller with 20A, 30A, or 40A and it must be dedicated to that speed controller.

20A may be a better choice if you are not sure that your gearing allows the FP to run fast enough not to burn itself up.

[RyanN]

Just a personal preference here. 20AMPs

No science or anything behind my reasoning (well... actually there is, but I'm not going to get into the heat dissipation stuff...)

That little motor has to get rid of a lot of heat just at 20AMPs. At 30 or 40AMPs, I can see that motor going up in smoke in a hurry if something goes amiss. At 20AMPs, you at least have a few trips before it really starts damaging the motor.

[Vikesrock]

Jim, I'm not really sure what your post is trying to say.

The FPs must be connected to a speed controller based on rule <R54-A> (as Eric mentioned).

These speed controllers can then be connected to 20, 30, or 40 Amp breakers. The required wire gauge is based on the breaker used.

If someone wants to run an FP off a 20 Amp breaker they would be allowed to do so. They could then use wire as small as 18 gauge to wire this branch. Depending on where on the torque/speed curve the motor is being run, this may or may not produce desired performance, but it is perfectly legal.

In fact, you could wire your CIMs through 20A breakers if you wanted (note: this is almost certainly a bad idea)

[Jim E]

In my wiring, I treat the FP as equivalent to a CIM.This motor is powerful and fragile. Allowing only 20A of current is pretty low for this motor, but I do not know what applications you have in mind for it. I prefer to stay on the high side of the curve rather than the low side.

[Al Skierkiewicz]

Nippon-Denso 18.6
Nippon-Denso 18.6
Keyang 11.8 19
Fisher-Price 70
Globe 21.58
CIM 133
Mabuchi 6.2
Banebots 37
Compressor start 25
These are the stall currents for the motors in the 2009 KOP.

<R54> All electrical loads (motors, actuators, compressors) must be controlled by relay or PWM output signals sent by the Digital Sidecar to an appropriate power regulating device
A. Each CIM motor and Fisher-Price motor must be connected to one Victor or Jaguar speed controller. They must not be connected to relay modules.
B. Servos must be directly connected to the PWM ports on the Digital Sidecar. They must not be connected to speed controllers or relay modules.
C. If used, the compressor must be connected to one Spike relay module.
D. Each other electrical load (motors or actuators) must be connected to one Victor or Jaguar speed controller or one Spike relay module.

Please note that only motors that are 20 amps or less stall current can be powered by relay(Spike) as that is the relay specification. An exception to this rule is the compressor which has a start current more than double it's run current. For this relay only you may substitute (read this as "should") a 20 amp circuit breaker in place of the relay mounted 20 amp fuse.

Any team may choose to run any motor from any breaker as long as the current rating and wire size rules are maintained. However, sound electrical practice and the rules allow you to size your breaker/wire/motor appropriately.
The 2009 game is unlikely to cause high currents in drive motors. That being said my normal recommendation for #10 wire to feed CIM motors and FP motors may not produce significant gains in this year's design only. Electrical rules allow you to use #12 wire with 40 amp circuit breakers (See R45 for all specifications) and #14 wire with 30 amp breakers. Therefore, should you desire maximum performance over all possible game conditions, my recommendations would be for #12 minimum for FP and CIM motors fed with 40 amp breakers. The Banebot motors can be fed with 20 or 30 amp branch circuits depending on your design, transmission and intended use. Please be advised that the Denso, FP and Keyang motors have internal thermal breakers in addition to any external electrical protection you provide.

[Tristan Lall]

Originally Posted by Al Skierkiewicz

Please note that only motors that are 20 amps or less stall current can be powered by relay(Spike) as that is the relay specification. An exception to this rule is the compressor which has a start current more than double it's run current. For this relay only you may substitute (read this as "should") a 20 amp circuit breaker in place of the relay mounted 20 amp fuse.

This year, any Spike may be operated with a 20 A circuit breaker in place. (Previously, only the one on the compressor could be replaced.)

[Al Skierkiewicz]

I believe that is a misprint, so I am awaiting an update. IFI specifications for this part require a 20 amp fuse.

[Racer26]

I have never seen any good reason to only allow it on the compressor. I'm aware that the compressor was blowing the 20A fuses and thats why they allowed it, but why stop there, who cares if we put the breakers in the other spikes too, sure, they'll probably never blow, but why run the risk of one blowing and losing that device for the rest of the match, when it could come back in a second or two.

[Vikesrock]

Originally Posted by Al Skierkiewicz

For this relay only you may substitute (read this as "should") a 20 amp circuit breaker in place of the relay mounted 20 amp fuse.

Actually this year you may do this for any relay per <R59-F>

<R59> The control system is designed to allow wireless control of the ROBOTS. The Driver Station, cRIO Mobile Device Controller, digital sidecar, breakout boards, power distribution module, speed controllers, relay modules, wireless bridge, batteries, and battery charger shall not be
tampered with, modified, or adjusted in any way (tampering includes drilling, cutting, machining, gluing, rewiring, disassembling, etc.), with the following exceptions:
...
F. The fuse on the Spike relays may be replaced with a 20 Amp Snap-Action circuit breaker.

[Al Skierkiewicz]

This is an IFI recommendation that First has applied in the past. Compressor start can go as high as 25 amps but run is only 10-12 amps. This is a guarantee to blow the fuse even though it is an extremely short duration. However, used in other services, a breaker could easily allow more than 20 amps continuous without trip which is enough to destroy the relay.

[JVN]

We are using 40 amp breakers on our FP motors because there are times when we want that extra power kick. The FP motor can handle 40 amps but only for short periods of time at high RPM. We know we could conceivably burn up a few if something goes wrong (gearbox jam, stall, etc).

More important than breaker sizing is watching your loads. FP motors have a very distinct smell when they burn up (the insulation on the motor windings burns off). The first time you blow one up, you won't forget it.

Watch your loads! Don't rely on the breaker to save the motor.

-John

[Mike Betts]

Originally Posted by JVN

...More important than breaker sizing is watching your loads. FP motors have a very distinct smell when they burn up (the insulation on the motor windings burns off). The first time you blow one up, you won't forget it...

John's advise is sound (as always). The FP suffers at "high loads" because it requires active cooling. Look at those vents at the rear and you will see fan impellers integrated into the motor assembly. This is why the body is so small in size compared to the power of the motor.

An FP at stall will almost immediately destroy itself regardless of the circuit breaker used (it might survive with a 20A, but I doubt it).

Bottom line, never stall a Fisher Price motor...

Regards,

Mike