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# Weld Positioner DC drive issue

#### dirk

##### Aluminum
We have an Koiki 2500 lb weld positioner withe a DC motor and drive for the rotary. The motor is a 180v 1 Hp Baldor, the drive is a Cleveland Machine Controls Pace Master MPA-04342. Although the motor is 180v (which was replaced at some point), they have the drive wired to 115v, so it only puts out 90v max. The problem is that the drive starts out at 90v, and the gradually drops voltage to a point where the motor stops spinning. What is wrong with the drive? Is it something that can be replaced, or do I need to install a whole new drive? Is it hurting the motor at all, that the drive is only putting out half the voltage the motor is capable of? Very rarely do we not have the pento at 100% full speed.

#### Cyclotronguy

##### Stainless
Perhaps the drive wants to see 240 Vac not 120 Vac.

#### markz528

##### Hot Rolled
You are measuring the voltage? What is the current doing?

#### JST

##### Diamond
You say the motor is a 180V motor, and the drive is for 180V, but it is powered by 115V?

Are you sure the voltage is only 90V?

I ask because some drives can "double" voltage, although the "90V" and "180V" types often are not set up that way.

Running a motor on low voltage can limit power and torque, so that the full 1 HP probably is not available.

That does not totally explain the slow-down, but most drives have current limits, which may be the culprit.

If the drive & motor are for 180V, the current would need to be double for 120V vs 240V, and the current limit would cut the output. That would require more current for the given power, so the current limit cuts in sooner, and that cycle can continue to a stop.

If the motor and drive are good for 240V input, why is that not used? The motor would have double the power capability for the same current limit at the higher voltage.

#### dirk

##### Aluminum
You say the motor is a 180V motor, and the drive is for 180V, but it is powered by 115V?

Are you sure the voltage is only 90V?

I ask because some drives can "double" voltage, although the "90V" and "180V" types often are not set up that way.

Running a motor on low voltage can limit power and torque, so that the full 1 HP probably is not available.

That does not totally explain the slow-down, but most drives have current limits, which may be the culprit.

If the drive & motor are for 180V, the current would need to be double for 120V vs 240V, and the current limit would cut the output. That would require more current for the given power, so the current limit cuts in sooner, and that cycle can continue to a stop.

If the motor and drive are good for 240V input, why is that not used? The motor would have double the power capability for the same current limit at the higher voltage.
The drive is double voltage, 115v AC- =90v dc, 230ac = 180dc. Its been wired that way since 1988, so I don't really see a need to change it. That being said, I ordered a Minerik drive that has a 115v doubler function, and will output 180v dc on. The drive out output voltage would drop, even if we disconnected the motor, so the drive appears to be going out.

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