[wireb]

Depends on what burned up. If just the sense resistors burned up then yes swapping that will fix your issue. But if the driver IC or PCB burned up then changing the resistor will not help anything. What current are you trying to drive? At the rated 5A this resistor will be trying to dump ~5.5W of power. Would go with a 7.5W or 10W resistor to be safe. Also make sure to use a non-inductive resistor or weird things may happen.

[gnarf]

Hi, I also have a "upgraded" version with TB67S109AFTG. Does anybody know why the supply voltage is limited to 40 (some times 42) Volt? As far as I read the data sheet of the chip says 50v absolute max and 47v normal max...

cu

Thorsten

[jfong]

Hi, I also have a "upgraded" version with TB67S109AFTG. Does anybody know why the supply voltage is limited to 40 (some times 42) Volt? As far as I read the data sheet of the chip says 50v absolute max and 47v normal max...

cu

Thorsten

You want some headroom. Fast deceleration of stepper motors creates voltage. When added to your power supply voltage can overcome the 50volt absolute max rating. This lets out the magic smoke.....

36volt PS is a standard value you can find easily. Sometimes they have a output voltage adjust that can be bumped up a few volts. I wouldn't use a power supply set greater than 40volts to play it safe.

[millhead]

On the subject of Power Supplies, I have seen people use grossly over rated power supplies.
Let's take an example : You have a stepper motor that takes 3 Amps, at 3Volts per winding. That is 9 Watts per winding, 18 watts for the two windings.
Add about 20% more for inefficiencies in the driver. That is a total of 21.6 watts for the drive and the motor.

So, if you are using a 24 Volt power suppply, you need less than 1 Amp from the 24Volt PSU. I have seen folks specifying a 6 Amp power supply for the above case.

My 3 axis mill has 3 motors, 295 oz-in each, which have 3A, 3V windings. I have used a 24V, 2.7Amp switching power supply for the past 7-8 years with no problems at all.

Daya.

[A_Camera]

On the subject of Power Supplies, I have seen people use grossly over rated power supplies.
Let's take an example : You have a stepper motor that takes 3 Amps, at 3Volts per winding. That is 9 Watts per winding, 18 watts for the two windings.
Add about 20% more for inefficiencies in the driver. That is a total of 21.6 watts for the drive and the motor.

So, if you are using a 24 Volt power suppply, you need less than 1 Amp from the 24Volt PSU. I have seen folks specifying a 6 Amp power supply for the above case.

My 3 axis mill has 3 motors, 295 oz-in each, which have 3A, 3V windings. I have used a 24V, 2.7Amp switching power supply for the past 7-8 years with no problems at all.

Daya.

You have applied the wrong logic, giving a totally wrong advice based on serious misunderstanding or lack of better knowledge.

Yes, 24V 2.7A supply MAY work, but it is not optimal. For high speed and acceleration you need high driver voltage. The higher the better, but you should not use higher PSU voltage than your driver allows. 24V is not optimal for the TB6600 based drivers, as I believe they perform best at 36V. The voltage over the windings has nothing to do with the PSU voltage.

The current is needed for higher torque, a 3A motor reaches maximum torque if you can feed it with 3A, but it works even at much lower than that, just not as powerful as it could be with higher current. How much current is used depends on how much load you have on your motors, if you are cutting air the load is very low but as soon as you start cutting real material with the optimal speeds and feeds the current will increase dramatically, until it can no longer increase and that may result in an overloaded PSU, at best case the output voltage will drop, or the fuse will pop or at worst case it will start to overheat and giving smoke signals.

Motors are inductive load, so you can't really apply Ohms law the way you did. When a motor starts it draws considerably more current than normal, so the PSU must be able to handle that to avoid overload. A stepper motor starts every time a new step pulse is given, so that happens very often. The PSU must be able to handle the number of motors you are using, in your case 3, and additionally you must allow for extra current needs, which is about 30% more. This is especially the case for switching supply. Do NOT confuse the motor current and calculate the PSU based on simple Ohms law which is about resistive load, because motors don't behave like resistors, so you actually need 3 x 3 A + 30% = 12A. You can call that over rated, I call that "rated right, according to specs". The PSU must be able to handle all the momentary overload situations, which you get when use inductive loads, like motors.

The fact that it worked for you for the past 7-8 years to use an underpowered PSU says nothing about how it should be done, so your advise should be ignored, not taken seriously because it is based on the wrong logic.