bridge rectifier & Capacitor for DC Motor

[jayt]

I need a 95VDC motor to run from regular household current (120v AC)
Motor Specs:1 HP, 9.1 AMPS, 4150 RPM, CW Rotation, 25 C Ambient, Open Const
1) I need to know what Bridge Rectifier I should use
2) I need to know what capacitor I should use
3) What kind of speed control can I use? (preferably something inline with the power supply. I had thought maybe a dimmer swith for lights???)

I have read enough on it to know #1 & #2 are the items I need. However there are so many choices to choose from so please be specific for a newbie. Thanks for any help!

 

[j.p.bill]

With a motor that size, you wil need a PWM speed controller. Lamp dimmers aren't rated for DC (they latch on, and stop controlling).

If you want to do it right, you need to find a transformer with a secondary voltage of 130 volts (center tapped) that is good for about 12 amps - you need the extra capacity for stalled condtions, so the breaker can pop before the transformer smokes.

A full-wave rectifier will do - any two stud mount diodes rated 400 volts and 20 amps (lots of capacity) will do. You will need a fairly large filter capacitor. I'd guess on the order of 10,000 microfarads, but someone will probably know better.

If the motor doesn't have to reverse, then a simple half bridge circuit will do for the speed control.

 

[RODALCO]

Get a 15 Amp variac. ( 0 to 130 Vac range ) Will give full speed control with some loss of torque at lower speeds.

Use a 400 Volts 35 Amps full wave bloc rectifier.

 

[jayt]

Bridge Rectifier & Capacitor for DC Motor continued

If you want to do it right, you need to find a transformer with a secondary voltage of 130 volts (center tapped) that is good for about 12 amps - you need the extra capacity for stalled condtions, so the breaker can pop before the transformer smokes.

A full-wave rectifier will do - any two stud mount diodes rated 400 volts and 20 amps (lots of capacity) will do. You will need a fairly large filter capacitor. I'd guess on the order of 10,000 microfarads, but someone will probably know better.

If the motor doesn't have to reverse, then a simple half bridge circuit will do for the speed control.

The motor has no need to go in reverse. However I will want it to be able to run way below the rpms it can go, almost down to 150 - 200 rpms at times.
Now that you are getting me on the right track, where is the best place I can buy this stuff? preferrably online, but doesn't have to be. Thanks for your help

 

[ericgibbs]

hi,
I would support Rodalco suggestion, its nice n easy.

If at some future time, you always add some back emf detection to adjust the
dc to control the speed/torque.

EricG

 

[cadstarsucks]

Get a 15 Amp variac. ( 0 to 130 Vac range ) Will give full speed control with some loss of torque at lower speeds.

Use a 400 Volts 35 Amps full wave bloc rectifier.

Wow, that would be pricey!

 

[cadstarsucks]

The motor has no need to go in reverse. However I will want it to be able to run way below the rpms it can go, almost down to 150 - 200 rpms at times.
Now that you are getting me on the right track, where is the best place I can buy this stuff? preferrably online, but doesn't have to be. Thanks for your help

Digikey.com ... I only know what we use off hand to driver bigger motors than that... I can not stress enough the necessity of heatsinking!

GBJ1510 @$2.21 should be plenty, stud mounts are a: overkill and b) expensive
(we use GBJ2506 to dive 20A into a motor)

I would recommend a FGH20N6S2 @ @2.34 as a low end part for reliability. You should really find one that has a lower Vce(sat), but it will cost more.

SMQ201VSN102MP45S @$4.24 is probably a good one to try for starters... 1000uF 200V 3ARMS. DO NOT GO LOWER IN VOLTAGE OR ARMS

Oh, and did I mention to make sure you heat sink the parts really well?

Dan

 

[jayt]

Thanks CadStarSucks for the Digikey.com info. It looks like the route I will go. The motor originally came off an old treadmill. I still have the electronic circuit board that went with it. I remember some of the sensors had went out a few years ago. I took a picture of the board because I am going to assume what I need is on that board already beings it run off house current when it did work.

I am pretty sure the bridge rectifiers are the black things heat sinked to the sides. They are 5 of them. Are they run in Parallel? I am not sure which part is the capacitor though. Is it the white porcelain looking piece?

I have a google education on what I have learned so far about electronics so bear with me.

 

[kchriste]

I am pretty sure the bridge rectifiers are the black things heat sinked to the sides. They are 5 of them. Are they run in Parallel?

Those are probably FETs and Duo-diodes.

I am not sure which part is the capacitor though. Is it the white porcelain looking piece

That looks like a 5 watt power resistor to me. Hard to tell from the blurry pic. Can you post a better one?

 

[jayt]

Thanks kchriste,

I hope this will help better. I also added the pic of how I would wire the rectifier and capacitor together. So was I right to assume the rectifiers are the black things heat sinked to the side?

(1) Would I parallel wire them?
(2) Would I use all 5?

 

[House0Fwax]

In your pictures the capacitors are the tall 'can' shaped items with a silver coloured top and a stripe down one side.
The heatsinked items are not rectifiers.
Rectifiers come in various shapes, but they all have four legs.
https://en.wikipedia.org/wiki/Diode_bridge
Diode bridge - Wikipedia, the free encyclopedia

 

[jayt]

OK, Here is what I am going to go with (check out attachment)
Looking at the picture:

(1) What rectifier would I use for the Motor Specs listed.

(2) What Capacitor would I use?

(3) What Speed Controller can I use?

(4) Where would the Speed Controller go? (I labeled 2 spot on the schematic)

I will hopefully purchase all the items from Digikey.com
After this one gets answered I will leave all you guys alone. I think I should have enough info to make this happen.

 

[cadstarsucks]

Thanks CadStarSucks for the Digikey.com info. It looks like the route I will go. The motor originally came off an old treadmill. I still have the electronic circuit board that went with it. I remember some of the sensors had went out a few years ago. I took a picture of the board because I am going to assume what I need is on that board already beings it run off house current when it did work.

I am pretty sure the bridge rectifiers are the black things heat sinked to the sides. They are 5 of them. Are they run in Parallel? I am not sure which part is the capacitor though. Is it the white porcelain looking piece?

I have a google education on what I have learned so far about electronics so bear with me.

I see no capacitor. It looks like you have a phase drive there. I am not sure as there are not enough power components for a PWM drive assuming those diodes are the bridge and I can not make out the component references.

I looks to me like you have 2 diodes and 2 SCRs for a phase controlled bridge and a freewheeling diode across the motor. It would make even more sense if you look and found they are all the SCRs with three being used as diodes.

For a PWM you would need 6 in that configuration. If they were dual diodes there would only be 4 as there would be 2 for the bridge, an IGBT, and a freewheeling diode. And you would need the capacitor.

The "white porcelain looking piece" is an inexpensive power resister use for over current protection.

Dan

 

[cadstarsucks]

In your pictures the capacitors are the tall 'can' shaped items with a silver coloured top and a stripe down one side.
The heatsinked items are not rectifiers.
Rectifiers come in various shapes, but they all have four legs.
https://en.wikipedia.org/wiki/Diode_bridge
Diode bridge - Wikipedia, the free encyclopedia

Ummm...there is no tall can shaped thing large enough to be THE capacitor. Only small ones there tho filter the the power for the control circuit.

There is no main capacitor in his piccys. It would be on the order of 1.5"x1.8" not 0.3x0.5".

Diodes only have two legs, duals three and bridges four. I will maintain that he has 4 SCRs in a controlled bridge.

Dan

 

[cadstarsucks]

Thanks CadStarSucks for the Digikey.com info. It looks like the route I will go. The motor originally came off an old treadmill. I still have the electronic circuit board that went with it. I remember some of the sensors had went out a few years ago. I took a picture of the board because I am going to assume what I need is on that board already beings it run off house current when it did work.

I am pretty sure the bridge rectifiers are the black things heat sinked to the sides. They are 5 of them. Are they run in Parallel? I am not sure which part is the capacitor though. Is it the white porcelain looking piece?

I have a google education on what I have learned so far about electronics so bear with me.

Playing catch up here... is there some reason you do not just fix that one? And how was it connected in the treadmill? Normally treadmills that use that sort of arrangement have the controller connected to the line and a huge filter (BIG inductor and BIG capacitor) after the controller.

Dan

 

[House0Fwax]

there is no tall can shaped thing large enough to be THE capacitor.
Dan

Oh, I wasn't suggesting that THAT was the capacitor to be used, I was pointing out what they look like.

 

[cadstarsucks]

Oh, I wasn't suggesting that THAT was the capacitor to be used, I was pointing out what they look like.

Sorry, it seemed as though you were pointing at them as the one under discussion.

Dan