Stepper motor current calculating

[m_c]

I'm finally getting around to resurrecting an old engraver, but have drawn a blank on a suitable datasheet for the Z-axis stepper motor.

It's a Japan Servo KP46BM2-017.

The label says it's DC6V, and 30 Ohms.
Would I be correct in assuming the required current will be 0.2A (6/30)?

[JohnHaine]

Sounds way too low, would expect at least 1 amp. Are you replacing the drivers?

[m_c]

That's why I'm questioning it.
It is only a small pancake motor, so 200mA could be about correct.

Once I get the bench cleared, I'll stick 6V through a coil and see how much current flows.

[m_c]

Done a bit testing earlier, and it appears the numbers are about right.
Applying 6V results in 190mA flowing, so not that far of the calculate 200mA.

It also makes the motor noticeably cog when turned by hand while under power, and after connecting up the original control box, the amount of cogging feels very similar.

It does mean my plan to use some basic enclosed TB6600 drives won't work, so I'll have to go for something even smaller.

[Robin Hewitt]

The Voltage written on a modern stepper is usually down around 1 Volt. They don't expect you to use 1 Volt, they expect you to use maybe 36V to overcome the coil inductance and then limit the current so it doesn't go pop.

There was a time, long ago, when people used the L200 stepper driver chip and 6 or 12V steppers were quite normal.

If you can turn the motor with 6V applied then maybe you have coils in series? Even then it doesn't sound at all right.

[m_c]

Robin, it's only a very small pancake motor from the 90s I'd guess.
It's only a 4 wire motor, and I only applied power to one pair at a time.

I'd guess torque will be measured in fractions of Ncm. It's only moving the Z-axis on a small engraver, so not that much torque should be needed.