R2020 running direct 120V + bridge (no transformer)

[nicad]

I have read where someone already asked this, and the response was to NEVER connect straight 120VAC to the servo drive through a bridge and no transformer-- because of safety.
Other than the safety reason, will the R2020 run OK with direct 120VAC supplied to it through a bridge (outputting ~170V)? Do not worry, I do not plan on actually doing this.

Thanks-
Colin

[Al_The_Man]

Originally Posted by nicad Other than the safety reason, will the R2020 run OK with direct 120VAC supplied to it through a bridge (outputting ~170V)? Do not worry, I do not plan on actually doing this.

120 is 120, wether it is isolated or not, and if it isolated, then it is normal to set up one side grounded as a local neutral anyway, or you could ground the DC common, but not both, if the DC is grounded then you would need to fuse both legs of the secondary.
It virtually ends up the same thing.
Al.

[rutexus]

Colin,

I have cautioned people against using line voltage for a power source without isolation. This is not only as a precaution against personal injury, but for the equipment.

One mismatched ground in a system could toast the PC and or other equipment in the machine. The ground in a wall outlet has a specific configuration. At the building circuit breaker panel neutral is connected to the ground wire. If you do no observe this and keep the neutral connected to the ground side of your bridge rectifier output you can provide a pretty direct short circuit. I have not tried to build a circuit to test this. I only rember the poor o'scope, probe and printer that suffered from failure to observe this precaution back in the 1970's when I failed to observe this ONCE.

Many times in electronics you don't get a second chance to make the same mistake on the same equipment.

I won't argue this point with anyone. Anyone choosing to power their system with an unisolated power supply has voided the Rutex warrantee in my opinion. The Rutex drives are designed to be used with an isolated supply.

Tom Eldredge
Rutex LLC

[Al_The_Man]

Originally Posted by rutexus If you do no observe this and keep the neutral connected to the ground side of your bridge rectifier output you can provide a pretty direct short circuit. I have not tried to build a circuit to test this. I only rember the poor o'scope, probe and printer that suffered from failure to observe this precaution back in the 1970's when I failed to observe this ONCE.

This means that you are grounding the DC common which is OK but then obviously you would definately have to isolate the 120ac, as you say otherwise you would blow the rectifier regardless of connection , if you are not grounding the DC common then it would not matter, you would have a grounded neutral to the bridge.
When using an 'scope, it should be automatic to check for live chassis.
Al.

[routerman]

You can do it, but its better to use 220 volt and just use half the bridge, then the negative can be the common which is at ground potential.

120 -------->|---------|
....Ignore these dots......|------ +170 V
120--------->|---------|

com -------------------------- - neg

You can run a Larken Viper servo drive like this since it has an Opto isolated output section.