2 or 3 pin plug for power supply?

[baoshi]

I bought a 2nd hand KENWOOD PA18-2 linear power supply.
This is a properly isolated lab power supply, with separate output +/-/GND terminals. However it is using a 2 pin power plug without ground pin. I have checked the GND terminal is actually connected to the chassis.
Is it correct for a power supply? Why not to connect GND?

[Psi]

Maybe someone has changed the plug?

It doesn't say EARTH, it says GND. So i guess its technically correct.

[baoshi]

Maybe someone has changed the plug?

It doesn't say EARTH, it says GND. So i guess its technically correct.

I checked and compared with other pictures on the net. The plug seems to be original japanese 2 pin type. Just wonder if it is the standard practice of only using 2 pin plug for power supply?

[David Hess]

All of the similar floating output power supplies I have used included a 3 pin power plug and connected earth ground, chassis ground, and a separate output ground terminal directly together.

If there is enough isolation and low enough leakage current then I see no problem with using a 2 pin power plug and forgoing the earth ground connection.  In that case, the output ground connection may serve to reduce common mode noise.

[macboy]

Personally, I would re-wire it with a 3 pin plug, with the chassis grounded. This is the usual way. If the equipment is built to Class II (double insulated) standards, then it would be "safe" to operate without a grounded chassis, but it is still safer yet to have a grounded chassis. Plus, it would be nice to have a true ground reference available when using the supply. Otherwise the ground terminal is useless.

[DanielS]

Plus, it would be nice to have a true ground reference available when using the supply. Otherwise the ground terminal is useless.

Not completely useless: there may be situations where you want to use circuit-ground instead of earth-ground while still having your +/0/- outputs floating relative to whatever ground is... such as when your power supply and whatever else your circuit is connected to are on different grounds and you want to eliminate ground loops as a variable in your troubleshooting.