I am done with linear power suplies

SLK001

Joined Nov 29, 2011
1,549
If you ever decide to work with DC motors, linear is the only one that is recommended for them.
I have some 2½ HP DC motors from treadmills that run thru all their speeds with power from a non-linear supply. I believe that all it is is 120V rectified to DC, then fed to the motor with a PWM signal using a bank of switching transistors.

But I could be wrong!
 

ian field

Joined Oct 27, 2012
6,536
I have some 2½ HP DC motors from treadmills that run thru all their speeds with power from a non-linear supply. I believe that all it is is 120V rectified to DC, then fed to the motor with a PWM signal using a bank of switching transistors.

But I could be wrong!
There might not be any right or wrong - different manufacturers use whatever control topology they feel most confident with.

Triac phase control was the standard - but its radio noisy.
 

nsaspook

Joined Aug 27, 2009
13,086
There might not be any right or wrong - different manufacturers use whatever control topology they feel most confident with.

Triac phase control was the standard - but its radio noisy.
I've had lots of headaches with TCR power supplies being replaced with fancy SMPS units of the same power. Without very careful extra emi filtering and shielding they tend to shutdown at the first sign of system instability instead on blasting through high power transients like the old SCR units did.

These guys were tanks that we repair instead of replace.
https://www.us.tdk-lambda.com/hp/product_html/tcrpower.htm

The replacements must be part French as they surrender at the first shot.
https://www.genesysdcstore.com/
 

MaxHeadRoom

Joined Jul 18, 2013
28,619
I have some 2½ HP DC motors from treadmills that run thru all their speeds with power from a non-linear supply. I believe that all it is is 120V rectified to DC, then fed to the motor with a PWM signal using a bank of switching transistors.
There are two basic types of T.M. controllers, one is a simple SCR bridge version, the other Mosfet PWM, in both cases the T.M. supply is connected directly across the line, i.e. no SMPS, transformer, or dedicated supply.
Max.
 

DickCappels

Joined Aug 21, 2008
10,152
Good point! A regulated SCR supply is a relatively painless way of lregulating the power of high powered power sypplies. Sometimes you can even get them to work correctly without losing semiconductors or suffering bodily injury.

If your ripple requirements are not stringringent you might find this kind of "nonlinear" power supply ideal for you.
 

SLK001

Joined Nov 29, 2011
1,549
There are two basic types of T.M. controllers, one is a simple SCR bridge version, the other Mosfet PWM, in both cases the T.M. supply is connected directly across the line, i.e. no SMPS, transformer, or dedicated supply.
Max.
I haven't looked too closely at the controller yet - it was a curb find. The motor is a popular brand, 2½ HPish output (don't remember the exact HP or brand). I plan on using the motor and controller to power a 14" wood bandsaw (also a curb find) to convert it into a metal bandsaw.
 

Thread Starter

Bogdan.m

Joined Apr 20, 2019
57
well, i have the electronics lab 0-30v 3A which never faild me so far, can u guys at least help me make it so it does at least 8A ? or should i open another threaad ?
 

DickCappels

Joined Aug 21, 2008
10,152
well, i have the electronics lab 0-30v 3A which never faild me so far, can u guys at least help me make it so it does at least 8A ? or should i open another threaad ?
Don't open another thread -you are possibly on the threshold of getting what you are looking for. If you were to start a new thread on the same subject it would be merged with this one anyway.
 

Thread Starter

Bogdan.m

Joined Apr 20, 2019
57
May I ask, what kind of circuits do you work on?
anything, the one that gives me problems are some power leds that draw 15A@12v(PWM is a no go because of flickering on video), and then there is my induction heater that i have to connect to different transformers every time i want a bit more power and it's annoying.

So, can this schematic be modified to get a few more amps ???schema.gif
 

Ioannis66

Joined Nov 7, 2012
45
Well, half the R7 should raise the current limit to double of what you have now.

Depending on the Q2 you may be able to place 2, 3 or 4 of Q4 in parallel with the addition of emitter ballasting resistors of 0,1-0,22 ohm and about 5watts.

Double or triple the C1 and D1, D2, D3, D4 sizing for the new current you want.

Of course the sizing of transformer also according to your needs.

That way yous should double or triple the output current.
 

Dodgydave

Joined Jun 22, 2012
11,285
You're limited to the Transformer Current output.. The rest of the circuit can be altered to suit,,,
You need to measure the maximum current it will give out on an AC load,then you can design accordingly.
 

AnalogKid

Joined Aug 1, 2013
10,987
So, can this schematic be modified to get a few more amps ???View attachment 175721
Yes.

Of course, you will need a properly sized transformer, maybe a higher-current bridge, and larger filter capacitors.

Depending on what the part types are for Q2 and Q4, they might work as is. If Q4 is a bit light, then either replace it with a part capable of 20 A collector current (always oversize semiconductors by 100%), or add another one in parallel (this requires adding "ballast" resistors to the circuit to guarantee current sharing).

ak
 

Analog Ground

Joined Apr 24, 2019
460
In college we had to build our own bench power supply. After reversing the output electrolytic capacitor and watching the oily, white smoke come out I decided power supplies would never be my thing. Buy. Don't build.
 
I bought stuff in the range of 0-40V, 0-30A by Kikasuii and Xantrex 10 or more years ago. Price then was $1500-$1800 USD. I wasn;t allowed to isolated 0-5 V readback analog inputs/outputs though. That card was like $500 USD.
 

Papabravo

Joined Feb 24, 2006
21,159
anything, the one that gives me problems are some power leds that draw 15A@12v(PWM is a no go because of flickering on video), and then there is my induction heater that i have to connect to different transformers every time i want a bit more power and it's annoying.

So, can this schematic be modified to get a few more amps ???View attachment 175721
If you understand the schematic -- I suppose. Do you really want to bite off a chunk this big?
 
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