I recently purchased used a "four head Maka oscillating chisel mortiser". It was built in Germany in 1965. There was a motor spec plate on only one of the motors. It reads - 3ph, 2.5 KV (4.1 FLA at 480V) and is indeed dual voltage. I can not speak with the former operators or maintenance people from whence it came in North Carolina.
Since there are no motor wiring diagrams, I can only guess that they are wired 480 since they run at this voltage but not 240.
The machine is designed to be able to run any or all (depending upon which of the manual starters are switched on) the motors during a typical 4 second cycle. While testing I noticed that one of the four motors was getting hot in only a few operation cycles. When I tested the other three motors together, they tripped the 30A panel breaker from which they're fed. I tested the draw with a clamp meter and amazingly each leg of the three read around 85 amps! I thought my meter was off so I tested my 15hp dust collector motor and after inrush it read about 20A - just right. So the meter works.
However, despite the fact that the meter reads such a high amperage they are not blowing the 11.5A thermal protectors in their individual manual starters.
What am I missing. I don't have a good grasp of the difference between wye and delta transformer and motor wiring. Could this be an issue?
Also, at least two of the motors were rewired internally since there are only three motor leads rather than nine.
I've attached a supply wiring diagram FYI
Too much information yet?
Thanks,
Bill
Since there are no motor wiring diagrams, I can only guess that they are wired 480 since they run at this voltage but not 240.
The machine is designed to be able to run any or all (depending upon which of the manual starters are switched on) the motors during a typical 4 second cycle. While testing I noticed that one of the four motors was getting hot in only a few operation cycles. When I tested the other three motors together, they tripped the 30A panel breaker from which they're fed. I tested the draw with a clamp meter and amazingly each leg of the three read around 85 amps! I thought my meter was off so I tested my 15hp dust collector motor and after inrush it read about 20A - just right. So the meter works.
However, despite the fact that the meter reads such a high amperage they are not blowing the 11.5A thermal protectors in their individual manual starters.
What am I missing. I don't have a good grasp of the difference between wye and delta transformer and motor wiring. Could this be an issue?
Also, at least two of the motors were rewired internally since there are only three motor leads rather than nine.
I've attached a supply wiring diagram FYI
Too much information yet?
Thanks,
Bill
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