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ATV58. Our customer assigned the output to setpoint reached. When the load becomes bit heavier, the output changes unsteadily. I proposed the customer...

Goals and Symptoms

ATV58. Our customer assigned the output to setpoint reached. When the load becomes bit heavier, the output changes unsteadily. I proposed the customer to use FTA with lower threshold than the speed reference instead of SRA. I am sure this problem will be solved. But the customer (the end user of the customer is DAIMLER CHRYSLER) strongly wants to know following things. 1. How can ATV58 detects the real motor F without connecting sensor? I explained this is detected roughly by the vectors of the current and voltage. The customer wants the documented explanation of the way to detect. Could you explain how ATV58 detects the motor frequency in more detail? 2. How wide of the width of SRA hysterisys is and how is the accuracy. I think the hysterisys should be greater than the speed precision, +-1%. Could you tell me the figure of hysterisys width and accuracy? As you know, DAIMLER CHRYSLER is very important customer for Schnedier. I appreciated it if you would answer ASAP.

Causes and Fixes

The first poin is to check the application if you have too many unsteadily. For the other point, the hysterisys are:

FTA: relay activation at -0,1 Hz of the targeted frequency, desactivation at - 0,3 Hz.

SRA : relay activation at - 0,1 Hz and + 0,1 Hz of the targeted frequency, desactivation at - 0,3 Hz and + 0,3 Hz.

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