Installing a new inverter

Installing a new inverter in place of older inverter models

1. Some older inverters may have a separate braking module connected to the DC bus of the old inverter.  

   If the new inverter has B1 and B2 terminals then the inverter has an onboard braking transistor.  The external braking module must be removed and the resistors rewired directly to the new inverter.  Normally there is an overload in line with the resistors, too.  This OL will stop the machine (drop the 3 wire) if tripped.  If the external braking module is connected to the B1 and B2 terminals of the inverter, damage to the inverter braking transistor is probable.  
   1. Some machines, like Extractors, need more braking capacity than the inverter itself can supply.  So, in these cases the external braking modules and resistors stay in the circuit and are connected to the + and - terminals of the DC bus.  
   2. It is possible to leave an external braking unit on the inverter and not use the internal braking transistor.  Follow the guidance of the latest schematic for your new inverter and machine model to make the right decision. See the note below.  

2. Rules of Thumb

   On low voltage (200 to 240 v) inverters, less than 25Hp (about 71 amps)  will have the dynamic braking circuit built in.  Any inverter rated 30Hp and above (85 amps) will need an external dynamic braking module.
   On high voltage (346 to 600 v) inverters, less than 30Hp (about 40 amps) will have the dynamic braking circuit built in.  Any inverter rated 38HP and above 38Hp (50 amps) will need an external dynamic braking module.

3. Braking resistors are dependent on model number and voltage. 

   These resistors are shown in the new schematic under "wiring changes" when you download inverter constants.  Make sure to pick the schematic for your eact voltage and machine model.  

4. Inverter constants are model and voltage dependent

   Constants can be downloaded from Milnor.com under the Safety/Support tab.  Voltage and model number are critical for proper programming.  

5. Some inverters have internal DIP switches that need to be switched properly

   Generally speaking, Milnor uses :
   1. Sinking voltage (not sourcing)
   2. voltage - 0-10V signals (not 4-10 ma)
   3. Internal Terminal resistance is ON.  (not off) 

The specific switches for the V1000 and A1000 are set as follows:

1. Switch S3 is set to SINK.  (Sink or Source)  
2. Switch S1 is set to V (0-10v)
3. Switch S2 is set to ON. 

Braking Resistor Terminals

If your machine has a braking module between the braking resistor(s) and the inverter, the + and - terminals are used rather than B1 and B2, and vice versa. 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. 

When installing a new inverter for a machine with braking resistors, it is important to determine whether the resistors need to be wired to terminals B1/B2 or +/-. The location of these terminals depend on the type of inverter you have. It is recommended to download the inverter technical manual and inspect the terminal block configuration on section 3.4. To verify the CIMR part number for the inverter, head over to this article to determine the correct terminal block configuration. Make sure whether or not the inverter has terminals B1 and B2 before installing braking resistors. Irreversible damage to the inverter may occur if the braking resistors are improperly installed.