Inverter with insulation monitoring device

Disclosed is an inverter which is provided with a first node, a second node, and an earthing point. A first switch provides a switchable connection path between the first node and the earthing point. A second switch provides a switchable connection path between the second node and the earthing point. The inverter also comprises the insulation monitoring device which is configured to measure first current when the first switch is closed and the second switch is open, and measure second current when the first switch is open and the second switch is closed. First equivalent insulation resistance between the first node and the earthing point and second equivalent insulation resistance between the second node and the earthing point are determined by the first current and the second current. The inverter is permitted to operate only when the insulation resistance value is lower than a preset threshold value.