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Test current sensor from Kone lift board

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2PAC Mafia

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Hello guys,

I have a Kone board from speed variator which controls a motor of a lift. At installation my customer get "Motor Overcurrent" alarm and the system is blocked.

OK, I already had this type of board before and I replaced a lot of things, IGBT, predrivers, PWM control IC, etc, but nothing solved the problem.

Now again I have a board with the same problem and I´ve been focused on the current sensors, it has two CSLA2F sensors. The theory of this sensor is two pin power supply and one pin voltage output which goes to MC33172 amplifier and LM339. I´ve seen I have 9V supply on them when I give power to the board and as I can´t simulate the real output at U, V, W from IGBT I passed a cable through the sensor and I created a current. When I haven´t current through the sensor I have 4,48V output and when I pass some current up to 2A through it nothing happen, voltage at output is not changing on them. What do I do wrong?
Any good idea to test them properly?

Thanks.
 

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Tony Stewart

Well-Known Member
Most Helpful Member
output is V+/2 at 0A and is +/- 120A full scale depending on number of turns, N. with 19.6mV per turn thru torroid using a Hall Effect sensor.

4.48V is close to 9/2, thus look for small mV changes per Amp.

MC33172 will have gain and offset control, relative to V/2 and maybe also a diode to rectify direction current to unipolar linear V out from 0-x? full scale.

LM339 may be a comparator for over voltage with a fix thresholds with a LPF filter at say 30A but ignore starting surge. check gain offset and reference V on LM339
 
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dr pepper

Well-Known Member
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Hi 2pac, we have 2 kone crane's here.
You say you pass current through the sensors (which I assume are current transformers), is this current ac or dc, some ct's can work with either, but some are ac only, plus the amount of current your using might be too low.
I have a couple of Abb current transformers which are active, and can measure ac and dc, they work by balancing out the magnetic field in the core, and the control voltage that does this is the current output signal.
Speaking of output signal, this may be a current signal, if this is the case the output needs a load resistor, if you remove the sensor from the circuit you'll just get full +vcc or gnd outputtted.
The other thing is the controller itself may well have eeprom and the fault may not be reset without a laptop and software, or a secret manufacts 'trick', more and more stuff is like this these days.
Unusual to see 3 ct's, usually drives just use 2, the third phase is assumed to be the same as the other 2, maybe being a lifting machine theres a safety reason for it.
 
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2PAC Mafia

Member
Hi,

thanks for your answers, finally I tested with magnetic field of a magnet removing the hall effect sensor and one of the sensors was broken. It has hall effect SS94A2 sensor.

In theory it´s from 0 to 125A and can work with DC and AC.
 

dr pepper

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Well done, I've never gone inside a current transformer and fixed it before, I hope you make a few bob out of this one.
 

2PAC Mafia

Member
Hi Dr Pepper,

They are not current Transformer, you can check the PDF attached or SS94A2 datasheet to understand how it works.

The magnetic field created on the sensor by the current passing through the cable is detected by the SS94A2 and then it is outputting voltaje.
 

dr pepper

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Most Helpful Member
Yes, I was using the term 'current transformer' loosely, as these things look and work like one, except they can measure dc too.
 
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