The
ov message displayed on the screen of your inverter indicates over-voltage, meaning that voltage in the DC bus has exceeded the acceptable range. This typically occurs during the deceleration process of a formula when the basket is commanded to slow down to a complete stop, particularly after wash or extract. During deceleration, the inverter is given a set amount of time (depending on the model of the machine) to slow down from its maximum output frequency to 0 Hz by transmitting current to the braking resistor(s). This time value is set as inverter constants via parameters.
An over-voltage fault may be caused by improperly-wired braking resistor(s). To verify this, use an ohm-meter to verify resistance across terminals
B1 and
B2 on the inverter (if your inverter does not have
B1/
B2, see the following paragraph). Take one wire loose from either B1 or B2 to check the resistance. Measure across the loose wire and the connected wire. This terminal is located on a V1000 inverter as shown in the image below. If there is no resistance reading, inspect the wiring and verify with the appropriate electrical schematic for your machine.
If your machine has a braking module between the resistor(s) and the inverter, the
+ and
- terminals are used rather than
B1 and
B2. This is usually seen in older inverter models or with inverters that have a quick slow down feature, like an extractor or larger washer extractor. Additionally, larger inverters may also not have built-in braking transistor and requires an external braking module.
The resistor(s) may also be damaged. A faulty braking resistor can cause over-voltage in the DC bus; particularly, an open circuit at the resistor. The resistance check will indicate this issue. Inspect the braking resistor for any visible damage. If the resistor appears cracked or reads open then replacement is necessary.
