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DRUM MOTOR MCU
21:1 HEATSINK TOO HOT
This error code is generated by the MCU. There is a temperature sensor (NTC) mounted on the
MCU cooling flange next to the power transistors in the output stage. If the temperature of the
cooling flange gets too high (> 90°C) the error code will be set to protect the transistors.
The cause of high cooling flange temperature can be e.g. a stiff drum in combination with intensive
use and high ambient temperature. There may also be an error in the motor (sticking bearings or
short circuit in windings, which impairs the efficiency of the motor).
Action
• Make sure the drum turns easily.
• Check the value on the error code counter for the error code.
• Check the last 8 MCU error codes.
• Start a 90°C normal program with load on continuous operation and measure the temperature of
the motor and MCU.
• Replace the defective part.
21:2 MOTOR TOO HOT
This error code is generated by the MCU. Each time the motor is started from stationary, the MCU
will first measure the resistance between two phases in the motor. The MCU processor governs
the output transistors so that a DC current flows between two phases in the motor winding. The
actuation of the transistors is a measure of the voltage applied to the winding and the resistance
can be calculated using the current and voltage values. The resistance can then be converted to
a temperature since the winding resistance at 20°C and the temperature coefficient are known.
If the average value of the four latest temperature readings is higher than the maximum motor
temperature (e.g. 150°C), the error code will be activated.
The cause of high motor temperature can be a stiff drum, possibly in combination with intensive use
and high ambient temperature. There may also be an error in the motor (sticking bearings or short
circuit in windings, which impairs the efficiency of the motor). There could also be a contact error in
the connectors between the MCU and the motor or an error in the motor cable. An error in MCU
temperature measurement circuits can also occur.
Action
• Make sure the drum turns easily.
• Check the value on the error code counter for the error code.
• Check the last 8 MCU error codes.
• Measure the three phases to the phase resistors on the MCU motor connector (disconnect MCU
and take the reading in the cable connector) to make sure they are the same.
• Start a 90°C normal program with load on continuous operation and measure the temperature of
the motor and MCU.
• Replace the defective part.
Summary of Contents for W555H
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