7
The motor can be infinitely adjusted via a friction wheel
drive unit but is operated in one position only. The power
output, rotational speed and torque of the motor are re-
garded as constant and are optimized for this operating
position. After the friction wheel drive the motor power
output is transmitted to the output shaft of the stirrer via
either the first or second stage of the subsequent manually
adjustable toothed gear train.
Drive
• Unpacking:
- Please unpack the device carefully.
- In the case of any damage a detailed report must be
sent immediately (post, rail or forwarder).
Unpacking
The speed can be infinitely adjusted between 60 and 2000
rpm 50 Hz; 72 and 2400 rpm 60 Hz. The machine can be
operated continuously and warms up during operation.
The generously proportioned cooling surfaces enable dis-
tribution and transference of heat to be as even as possible.
Useful information
• Delivery scope:
-
RW 20 digital
overhead stirrer
- user guide
- chuck key
- warranty card.
The two meters long mains lead makes it possible to work
on stands - even with high glass apparatus under vapor ex-
traction hoods - without extension leads.
The precision stirrer shaft is designed as a hollow shaft to al-
low the stirrer shanks to be in serted.
Neglecting all losses, the power at the output shaft dur-
ing power transmission (conversion) is always as great as
the power output of the motor. The gear train merely pro-
vides rpm and torque conversion, which can be described in
purely theoretical terms by the characteristic curve plotted
in
Fig. 2
.
Friction wheel wear is kept low by a helical clutch matched
to the gear train. The down-pressure required at the fric-
tion wheel is adjusted by the helical clutch according to the
moment acting on the stirrer shaft. A low torque results in
a low down-pressure; a high torque results in a high down-
pressure.
The ball race capacitor motor is maintenance free. In its wind-
ing it carries a special overheating circuit breaker (self-locking
temperature limiter) which shuts down the motor perma-
nently if the permissible motor temperature is exceeded.
This special type of circuit breaker is used when the auto-
matic reactivation of the protected unit after overheating is
undesirable or impermissible. The principle of the tempera-
ture limiter is that of a switch that heats up and isolates the
motor from the power supply when the maximum permis-
sible temperature is reached.
Motor circuit breaker
When the self-locking temperature is exceeded,
Err. 5
is
shown on the display (see section “
Error codes
“).
In this case the unit can only be switched back on after it
has been switched off for approx. 4-5 minutes by pressing
the rocker switch (
A
, see
Fig. 1
) on the front or by discon-
necting the mains plug.
After this short cooling, the contacts in the current circuit
are closed again and the unit is operational once more.
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