STMBL Driver DC Bus Options

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3 months 1 week ago #347878 by reboots
Replied by reboots on topic STMBL Driver DC Bus Options
I went for the skookum SMPS on my Deckel FP2NC. 240VAC input, 160VDC 5KW output to match the existing Siemens servos. I found this item as cheap surplus, and bought two for insurance.

For the spindle I used a no-name import 220V-to-380V inverting VFD. Name-brand examples from ATO below:

www.ato.com/220v-to-380v-vfd

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3 months 1 week ago #347894 by PCW
Replied by PCW on topic STMBL Driver DC Bus Options
A 160V DC bus supply can only provide about 110 VAC to the motor
so you would be limited to about 1/2 the servo motors full speed.

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3 months 1 week ago #347915 by reboots
Replied by reboots on topic STMBL Driver DC Bus Options

A 160V DC bus supply can only provide about 110 VAC to the motor
so you would be limited to about 1/2 the servo motors full speed.
Can you clarify this? I had thought DC servo drives were typically an H-bridge, which would make for +/-160VDC output minus power semiconductor voltage drops. (Bipolar transistors in my Bosch drive, so not negligible.)

160V seemed reasonable for the 163V rating of my brushed DC servos. OP has 210V brushless servos, so their supply requirements are somewhat different.

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3 months 1 week ago - 3 months 1 week ago #347916 by NWE
Replied by NWE on topic STMBL Driver DC Bus Options

160V seemed reasonable for the 163V rating of my brushed DC servos.
 
Brushed DC servos, yes, that is correct, but not for AC motors:

Look at an oscilloscope trace of 120VAC sine wave. The tops and bottoms of the trace touch +/- 170VDC, you can't create that off 120VDC with an h-bridge.

This will also cause a bridge rectifier+capacitor to produce ~170VDC from 120VAC.

I still remember my first experience with a rectifier, how amazed I was to get about 17VDC when I powered it with 12VAC from a transformer. The 12VAC is the actual power, sort of an average. "Average" is not technically the correct term here, but it is the idea. RMS is the term normally used.
Last edit: 3 months 1 week ago by NWE.
The following user(s) said Thank You: reboots

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3 months 1 week ago #347917 by PCW
Replied by PCW on topic STMBL Driver DC Bus Options
Yes, a 160V  bus supply is good for 163V BRUSHED motors, Sorry I mixed you up with the OP (with BRUSHLESS motors)
The following user(s) said Thank You: reboots, NWE

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3 months 1 week ago #347918 by tommylight
The following user(s) said Thank You: reboots, NWE

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