1+ kW 150-200 VDC PSU ?

[andy55]

for my sanyo denki P5 100VAC servos I need a powersupply that gives around 150-200VDC. I'll use three 400W servos for moving XYZ axes, and one 1kW servo for the spindle. So I need either two ca 1kW PSUs or one big 2+kW PSU.

hmm... looking at the specs I wonder if the motors are rated according to mechanical output power ? the electrical input power seems even larger, by a factor of two !?

So, I wouldn't like to design everything from scratch and also not pay huge $ for new equipment... any ideas ??

I've been told that the PWM of the servodrives is not such a 'nice' load, so that PFC is probably required.
A switchable ballast resistor is probably also required to absorb the regenerated current during decceleration/braking.

[NC Cams]

Unless I"m horribly wrong, 100 Vac servos are not going to run all that well or for very long on 150-200 Vdc.

With regard to PWM with respect to DC, each time the control is "on", you need to supply 100% of the current that motor is "asking for". If you know what the locker rotor current is, that is how much the P/S must be capable of supplying without encountering an appreciable terminal voltage drop.

This will assure a reasonable factor of safety as you'll seldom see locked rotor current loads unless you see a PWM duty cycle of 100% which most switchers won't allow.

The more you cheat on this, the more voltage and speed drop you'll see as you load the system down.

[andy55]

Originally Posted by NC Cams Unless I"m horribly wrong, 100 Vac servos are not going to run all that well or for very long on 150-200 Vdc.

the drives are full bridge drives i.e. can supply the DC rail voltage in either direction through the motor coil.
100VAC motors means, I think, that the peak peak value of the sinewave voltage in either direction should be sqrt(2)*100 = ca 140 V. To account for some switching lossess the DC rail should be a little higher, maybe 150-200 V. The exact value won't matter because the drives have current feedback.

With regard to PWM with respect to DC, each time the control is "on", you need to supply 100% of the current that motor is "asking for". If you know what the locker rotor current is, that is how much the P/S must be capable of supplying without encountering an appreciable terminal voltage drop.

my understanding is that a motor coil is a very inductive load and that the pwm-frequency is so high as to make the current requirement seem close to continuous.
Yes, the P/S must probably be able to deliver max rated current for short periods, hopefully not for all three axes simultaneously...

This will assure a reasonable factor of safety as you'll seldom see locked rotor current loads unless you see a PWM duty cycle of 100% which most switchers won't allow. The more you cheat on this, the more voltage and speed drop you'll see as you load the system down.

Yep. Over-rating the P/S is probably a good idea so that it won't be the performance limiting factor.