18 volts throigh a 12 dc motor

[dtgprinter]

18 volts dc through a 12 volt dc motor. the motor operates a hydraulic pump. no electronics other than a coil relay to close the motor circuit. i would still just wire the relay 12 volts. Whole thing is to operate a 1 inch bore RAM. 1000lbs pushing capacity. I'm hoping to speed it up a bit. Operates 1 minute max then a few off. Only about 10 cycles per hour, an hour a day. Currently uses a rep cycle rv battery. Looking to replace it with 3 - 6 volt instead. Thoughts?

 

[desertfox]

Just wondering how long it will take your motor to overheat! not very long by the sounds of it.
My advice buy a motor to do the job.

 

[dtgprinter]

Thanks desertfox. I understand it would generate more heat. My question was more whether the small over voltage would create too much heat given the short run time and very low duty cycle. A larger motor is not really an affordable alternative because the pump and motor are one assembly. The motor is designed for 100% duty cycle so I thought this intermitent use at overvoltage might be perfectly acceptable.

Greg

 

[Walterke]

Seems like you've entered the realm of trial and (hopefully no) error.

P.S.: A 50% increase in voltage may not be a 'small' amount.

How long do you want it to work. Is it for a specific job, or will it be working like this for an extended time?

NX 7.5.5.4 with Teamcenter 8 on win7 64
Intel Xeon @3.2GHz
8GB RAM
Nvidia Quadro 2000

 

[desertfox]

I think stopping and starting is the problem running continuously at normal voltage is okay.
Get some advice from your electrical department i think they will advise no.

 

[Eltron]

It isn't just the voltage on the DC motor that you have to worry about. The over-voltage will allow the motor to draw more current. That's what's going to heat you up and burn you out. Imagine a starter motor for your car. They are rated for 12V, but their duty cycle is very low. If you run it at 12V for a minute you better look for a new starter. However, you could most likely run the same motor indefinitely at 3V. I think Walterke has it right. This may be a bit of trial and error. Maybe you could hook up a potentiometer to dial up the power as needed?

Dan

http://www.eltronresearch.com

Dan's Blog

 

[btrueblood]

" I'm hoping to speed it up a bit."

If the ram operates for a significant portion of its stroke with little or no load, then you might look into getting a two-speed hydraulic pump. Alternatively, have two motors, the new one running a high-flow, low-pressure pump, although you need a bit more plumbing and/or control logic to operate it.

 

[MiketheEngineer]

50% over is NOT small. Hey, what do you have to lose. Try it and see if it works. Worse case scenario, you go back to 12V and/or buy a new motor!! I am always big on "experimenting"!!

Let us know....

 

[tygerdawg]

Even though it is "an hour a day", it is still 10 starts per hour. The "starting" action, with it's inrush current, does all the damage. If you goose it with +50% voltage, 10X per hour, expect failure over time. Motors are designed for steady state operation. You upsize the motors (more thermal mass for heat dissipation) for multiple starts/hour. I assume you do not have any definitive info from the manufacturer about higher voltage operation and acceptable quantity of starts/hour.

You could always just try it and see how long it lasts.

TygerDawg
Blue Technik LLC
Virtuoso Robotics Engineering

http://www.bluetechnik.com

 

[dtgprinter]

The time savings won't be enough to warrant "trial by smoke". If I had gotten a concenses here that given the duty cycle / application it wouldn't be a problem I would have gone ahead but obviously there are two many variables. I suspect, given the mass of the motor and the industrial application of it's first purpose, that it would propably be fine but given the feedback I will leave well enough alone. Thanks for the feedback.

 

[Walterke]

would it be possible to start the motor at 12V and then gradually increase it to 18V? Might reduce some of your problems.

NX 7.5.5.4 with Teamcenter 8 on win7 64
Intel Xeon @3.2GHz
8GB RAM
Nvidia Quadro 2000