Hoist motor load test failure
Hoist motor load test failure
(OP)
Dears,
i have a single jip machine and i face a problem with it.the drum winch motor is working properly when there is no load & when i test it with load the motor is not moving correctly.
Site conditions:
380V 60Hz
Motor conditions:
3phase motor @50Hz : 230/400V D/S - 4.87/2.81A D/S - 1.10KW - 1395r.p.m
@60Hz : 265/480V D/S - 4.87/2.81A D/S - 1.27KW - 1675r.p.m
please advice where i can expect the failure?? and what will be suggestions.
thank you
i have a single jip machine and i face a problem with it.the drum winch motor is working properly when there is no load & when i test it with load the motor is not moving correctly.
Site conditions:
380V 60Hz
Motor conditions:
3phase motor @50Hz : 230/400V D/S - 4.87/2.81A D/S - 1.10KW - 1395r.p.m
@60Hz : 265/480V D/S - 4.87/2.81A D/S - 1.27KW - 1675r.p.m
please advice where i can expect the failure?? and what will be suggestions.
thank you





RE: Hoist motor load test failure
"Will work for (the memory of) salami"
RE: Hoist motor load test failure
i want to clarify from you what will happen if i change the motor power wiring from star to delta, because i think if the supply power not enough, i may use delta wiring to reduce power required to run the motor.
RE: Hoist motor load test failure
If you change the motor connection from Star (380V) to Delta (220V), and then connect it to your 380V supply, you will be applying 1.732x as much voltage as the windings are designed for. The motor will produce a potentially very destructive initial torque surge, followed immediately by saturation, which will severely over heat it and likely destroy it in short order. It will run WORSE than it does now.
The two suggestions I already made are your only viable options in my opinion. Most likely someone is not going to like it because of the cost, but the truth hurts sometimes. Someone should have paid more attention to details before purchasing it.
"Will work for (the memory of) salami"
RE: Hoist motor load test failure
In star it is designed for 480V @60hz and you're giving it 380V@60hz. Torque vs speed curve is reduced by approx (380/480)^2. You don't way what failure you are having, but I imagine it may stall and trip. If you make it to full speed, current for a given horsepower would be higher by approx 480/300 and motor should be derated.
In delta, you would be giving it too much voltage. You would have torque capability to accelerate and run the load, but the core would be over-excited. You would have high/non-sinusoidal magnetizing current and increase in core heating. The motor might overheat and fail even at currents below the overload setting.
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(2B)+(2B)' ?
RE: Hoist motor load test failure
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Hoist motor load test failure
RE: Hoist motor load test failure
i think zlatkodo is right you should rewind the motor from 400v at 50 hz to 380 at 60 hz.
RE: Hoist motor load test failure
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Hoist motor load test failure
actually i cannot make any change in the motor of my machine. i can only use transformer to solve this problem,but i need to know should i use transformer for this motor only or for the full machine?.
for information this motor is part of BMU Machine which consist of Motors for different functions as Slewing motors, Travelling motors, pump motors and lifting motors. all of these motors are working properly with 60hz except the drum winch motor that i mention about it before.
RE: Hoist motor load test failure
if the other motors work well with the supply you have , you need to use the transformer only for the motor you have problem with.
good luck
RE: Hoist motor load test failure
Transformer sizing:
Add the currents of all motors.
This current must flow through the 120 Volt windings of the transformers.
Multiply the current by 120 Volts to get the VA required to supply the whole machine.
Buy two of the next larger standard size transformers.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Hoist motor load test failure
=====================================
(2B)+(2B)' ?
RE: Hoist motor load test failure
Your drum motor in question is designed to accept a V/Hz ratio of 8:1, your site has a V/Hz ratio of 6.33:1, so your motor (in Star) is being under excited and you have lost significant torque. Your motor PEAK torque, which is quite often needed in hoists, will be reduced to roughly 63% of the motor's design rated peak torque, that is a very serious problem on a hoisting application. So in order for that motor to produce designed torque at 60Hz, you must give it 475V as waross explained (a third option that I failed to think of by the way, kudos Bill).
Assuming that ALL of your motors are rated for 50Hz and getting 60Hz, you will have a similar issue throughout this system and I would suggest either boosting the voltage to 475 for any of them in such a condition, or replacing them with properly rated motors.
"Will work for (the memory of) salami"
RE: Hoist motor load test failure
RE: Hoist motor load test failure
Bill
--------------------
"Why not the best?"
Jimmy Carter