|
Post by holajonathan on Nov 20, 2021 13:15:36 GMT -5
This is a good price for a 1/2 HP dc motor from a respected brand. www.surpluscenter.com/New-Arrivals/1-2-HP-1800-RPM-12-VDC-Hypro-Pentair-Motor-2570-0026-10-3309.axdSince it is a DC motor it is efficient and speed control is simple. Could have a lot of uses in variable speed DIY lapidary equipment. My concern is that it has an intermittent 75% duty rating. It is a TENV motor (totally enclosed non-ventilated) so the duty rating must be to prevent overheating. Sealed, non-ventilated motors get hot. But cooling is easy with a small externally mounted fan like this. Does anyone have an opinion on this motor for DIY equipment? What does a 75% intermittent duty means? I know it means 75% on / 25% off. But at what interval? 3 minutes on / 1 minute off? 45 minutes on / 15 minutes off? Thank you.
|
|
nik
spending too much on rocks
Member since May 2019
Posts: 315
|
Post by nik on Nov 20, 2021 18:20:37 GMT -5
Not exactly sure how the duty cycle rating translates to real would use, and I'm sure it would be dependent on a number of loading and environmental factors. But something to con sider is that 1/2 hp at 12 volts works out to somewhere north of 30 amps, so coming up with a power supply and wiring that will work in a potentially wet setting will likely be more expensive than you think.
I have used servo motors intended for industrial sewing machines with a fair bit of success, but those are a little sketchy around water as well
|
|
|
Post by knave on Nov 20, 2021 20:18:33 GMT -5
DC motors are not my area of expertise, but I am very familiar with AC motors.
The duty cycle is almost certainly a (FLA) full load amp rating, For example my motors have a (SF) service factor, ie. 1.25 SF means that a 10 amp rated motor won’t trip on thermal OL (overload) until 12.5 Amps.
My assumption would be the intermittent duty cycle is loosely the same, The listed amps are good for 75% runtime allowing some cool off time. The intermittent rating specifically means the motor does not need to cool all the way down to room temp before restarting.
Ok to get useful info we would then arrive at 30A FLA X .75 = 22 Amps
If using as a sphere machine, you will likely run a lower voltage to get the rpm down. Still, the 20ish amps would be all you can run. You can’t raise the amps just because you dropped the voltage.
I hope this rambling makes a wee bit of sense.
|
|
|
Post by holajonathan on Nov 21, 2021 1:00:02 GMT -5
Not exactly sure how the duty cycle rating translates to real would use, and I'm sure it would be dependent on a number of loading and environmental factors. But something to con sider is that 1/2 hp at 12 volts works out to somewhere north of 30 amps, so coming up with a power supply and wiring that will work in a potentially wet setting will likely be more expensive than you think. I have used servo motors intended for industrial sewing machines with a fair bit of success, but those are a little sketchy around water as well I've got good 30 amp and 36 amp IP67 (waterproof) 12v power supplies. A whole bunch of them, actually. Meanwell brand. They should take care of the power.
|
|
|
Post by holajonathan on Nov 21, 2021 1:05:58 GMT -5
DC motors are not my area of expertise, but I am very familiar with AC motors. The duty cycle is almost certainly a (FLA) full load amp rating, For example my motors have a (SF) service factor, ie. 1.25 SF means that a 10 amp rated motor won’t trip on thermal OL (overload) until 12.5 Amps. My assumption would be the intermittent duty cycle is loosely the same, The listed amps are good for 75% runtime allowing some cool off time. The intermittent rating specifically means the motor does not need to cool all the way down to room temp before restarting. Ok to get useful info we would then arrive at 30A FLA X .75 = 22 Amps If using as a sphere machine, you will likely run a lower voltage to get the rpm down. Still, the 20ish amps would be all you can run. You can’t raise the amps just because you dropped the voltage. I hope this rambling makes a wee bit of sense. This does make sense. Thank you. To confirm, if the load is moderate, I can probably run it continuously, right? And if the duty cycle is just a cooling issue, I could attach some metal fins to it along with a little fan, and that would take care of cooling. Or just a fan would probably work. It's amazing how much heat even a small fan will pull off a motor.
|
|
|
Post by knave on Nov 21, 2021 3:44:54 GMT -5
Yes, I think at a lower amperage it is a 100% duty cycle motor.
|
|
|
Post by Rockoonz on Nov 21, 2021 3:51:06 GMT -5
Not exactly sure how the duty cycle rating translates to real would use, and I'm sure it would be dependent on a number of loading and environmental factors. But something to con sider is that 1/2 hp at 12 volts works out to somewhere north of 30 amps, so coming up with a power supply and wiring that will work in a potentially wet setting will likely be more expensive than you think. I have used servo motors intended for industrial sewing machines with a fair bit of success, but those are a little sketchy around water as well I converted my old Graves Mk1 faceting machine to a Consew 1/2HP servo, the only thing about it that I might call sketch is using the lever intended for a pedal. The narrow link belt to fit between the narrow metric pulley on the motor and the standard pulley on the facetor is also less than optimal. Works beautifully, though, and no indication that will change, and should work much better on the Sapphire facetor that is up for next conversion.
|
|
|
Post by Rockoonz on Nov 21, 2021 4:00:01 GMT -5
I agree that the duty cycle is most likely load dependent, would be interesting to learn the actual load. HP and torque as advertized can be a lot different from what you get in use, but most lapidary machines really don't need much anyway.
|
|
|
Post by knave on Nov 21, 2021 4:00:56 GMT -5
|
|
|
Post by holajonathan on Nov 21, 2021 10:29:39 GMT -5
Thanks for your investigation and help on this. I am going to buy one. I will report back when I get a chance to mess around with it.
|
|
|
Post by holajonathan on Nov 21, 2021 10:34:46 GMT -5
MSRP on this motor is $335, so $60 is a heck of a good deal. Pentair uses the motor to drive a high pressure pump, so it should be pretty robust. It's 26 lbs, so it should have a lot of steel to help dissipate heat. I like the sealed design for lapidary equipment.
|
|
|
Post by knave on Nov 21, 2021 11:35:00 GMT -5
“An example of a 75% Duty Cycle Motor is = 45/ [45+ (60-45)]*100 = 75% or 45 minutes on time per hour of operation at maximum rated pressure and flow. ON TIME can be extended by reducing the maximum pressure the pump operates at.”
In your case you may be able to read the amperage directly on your power supplies.
I’m very excited to see how this turns out. It looks very promising. Remember another member here used drill motors at 100% duty cycle and has made 100s of large spheres.
|
|
|
Post by catmandewe on Nov 21, 2021 11:54:47 GMT -5
Along time ago I found a screaming deal on some gear motors so I bought some for feed motors. they were intermittent duty motors, they are 120v but they run 30 seconds on, 30 seconds off, 30 seconds on, etc.
Let us know how these work.
Tony
|
|
|
Post by holajonathan on Nov 21, 2021 12:20:34 GMT -5
knave I saw that in the manual too. I'm going to try to power it with one of these. They are marketed as LED power supplies, but I don't see any reason it won't power a DC motor. The cool thing about these Meanwell power supplies is that you can adjust the voltage and they will maintain that voltage under load, increasing current as necessary. In other words, they are constant voltage power supplies. But if the power supply hits max output, rather than burning up or tripping an overcurrent protection circuit, it will reduce voltage and increase current, while maintaining max power output. In other words, I can set it to 15v DC output, and it will maintain that voltage up to 32A. If the motor needs more than 32A to generate the necessary torque, the power supply will drop the voltage and provide more amps. Speed would slow down, but the power supply will continue to supply maximum power without burning up or shutting down. That is how you would expect a motor to function under load, but most DC power supplies don't work that way.
|
|
|
Post by knave on Nov 21, 2021 12:32:49 GMT -5
That’s odd to me. Most led drivers are constant current since resistance through the diodes can vary bulb to bulb. (I think)
|
|
|
Post by holajonathan on Nov 21, 2021 14:02:24 GMT -5
That’s odd to me. Most led drivers are constant current since resistance through the diodes can vary bulb to bulb. (I think) I've seen constant voltage drivers used with LED lights that already have current regulation built in. For example, LED strip lights have current-limiting resistors in line with each LED. Since the current is already being regulated, a constant (and adjustable) voltage allows for dimming while maintaining an even light output across the strip of lights. With a constant current driver, you can't adjust voltage. The driver does that automatically to maintain current, so no dimming. You can also control LED output by controlling current, but to maintain even brightness with strip lights, you would have to regulate voltage at each led, which is more complicated (or at least more expensive) than regulating current. I think you're correct that high power LED (commercial) fixtures usually have built in constant current power supplies.
|
|
quartz
Cave Dweller
breakin' rocks in the hot sun
Member since February 2010
Posts: 3,352
|
Post by quartz on Nov 21, 2021 23:41:03 GMT -5
That motor looks to have a fairly short shaft, maybe not enough to fit my solution. I've cooled air over motors by adapting an alternator fan to the shaft, in some cases on a hub just for the fan with the pulley outboard of that, and the fan mounted directly to the pulley on others, dependent on available shaft length. This works quite well, keeping the motors cool as...well, the proverbial cucumber. Few, if any, alternators today have external fans like they did some years ago. The electrical shop at my local auto parts/industrial supply has a drawer full of them yet.
|
|
|
Post by knave on Nov 21, 2021 23:43:29 GMT -5
Really nice to hear how the dimmable led strips work. Very good.
|
|
|
Post by holajonathan on Nov 22, 2021 0:14:59 GMT -5
That motor looks to have a fairly short shaft, maybe not enough to fit my solution. I've cooled air over motors by adapting an alternator fan to the shaft, in some cases on a hub just for the fan with the pulley outboard of that, and the fan mounted directly to the pulley on others, dependent on available shaft length. This works quite well, keeping the motors cool as...well, the proverbial cucumber. Few, if any, alternators today have external fans like they did some years ago. The electrical shop at my local auto parts/industrial supply has a drawer full of them yet. The idea of mounting a fan on the shaft is brilliant. I've got some double shaft blower motors lying around and your solution would be great for those motors: drive a pulley with one shaft and stick a fan on the other shaft. They actually could use some cooling if used for something other than running a blower. The air being moved by a blower provides some indirect cooling, but using a blower motor to drive a pulley does not. I will keep your idea in mind when thinking about how I am going to work with the short shaft on this motor, as well. Thanks.
|
|
|
Post by holajonathan on Nov 22, 2021 0:20:36 GMT -5
Really nice to hear how the dimmable led strips work. Very good. It sounds like you know more about electrical than me, but I'm really into LED lights. Talk about a technological revolution. I've got an LED flashlight that is about as powerful as a 1000 watt halogen search light, commonly used until very recently. LEDs + high drain lithium batteries are an incredible combo. It's like having the sunshine in your pocket.
|
|