BTW, here is something that many have used as a guide and is a set up for disaster and has caused shorted outputs of the BOB etc, causing the relay to stay on.
The PDF shows a 20amp relay to operate a VFD ~20ma input!
But the significant error is there is no BEMF diode fitted across the relay coil.
When a relay such as this opens, there is a very large BEMF which can be in the order of several hundred volts.
The output device is usually either a mosfet or by-polar transistor, the rating of which is generally typically ~60vdc.
This can, and has, resulted in the shorting of the output device causing the relay to stay on.
Al.