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DC or AC drive for extreme temperature

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eeprom

Electrical
May 16, 2007
482
Hello,
I am looking for a motor speed control device to run a 1.5 Hp motor, could be AC or DC. I need to position a gate up and down, so the motor of course must be reversible. The speed (currently) is a constant 1750 rpm, and so the positioning is done by pulsing the motor on/off with a timer. I would like to replace this using a DC drive and a PI controller. The problem is that the environment is extremely cold, as low as -30 to -40F. A VFD wouldn't live very long in such temperatures. The power is not reliable, and so having a heater on site is also unreliable.

Any ideas on drives that can handle such low temperatures?

thanks
EE
 
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Maybe a silly question, but if if power is unreliable, how would ANY motor open the gate reliably, VFD or not?

Can you remote-mount the drive in a warmer location and run wire / conduit to your motor location? At that temp, I'd be looking carefully at the motor as well. Very well might have to utilize low-temp bearing grease, etc... I'd also have similar concerns about the gearbox, and anything else with moving parts.



SceneryDriver
 
The gate would not move if there was no power. Nothing can be done about that short of a generator.
 
The drive is not necessarily the problem, it's the capacitors in the rectifier that is. If you had a DC power source, i.e. batteries, you could conceivably solve both problems with a DC-DC drive, something like what is used on DC powered vehicles, they would not have an on-board rectifier with electrolytic caps.

But what's going to charge the batteries in that kind of cold? You may have to have a custom solution fabricated for you. I did one a long time ago where I had an input contactor for the AC that was tied to a a thermostat that stays open until the temperature rises above 10C. That way the power was kept off of the capacitors until the ambient was above freezing for long enough to ensure they were OK. The end user hated having to wait, bypassed it and blew the caps the first time he used it after that. But it worked fine up to that point.

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Thank you. That is an excellent idea.
 
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