Toshiba TOSVERT VF-AS1 Instruction Manual page 12

* Caution in case of using open collector encoder connection
In case using pulse command oscillator and open collector encoder, the rise time of the
voltage when the transistor is OFF tends to be longer than the fall time at the time when
the transistor is ON. Therefore, if the maximum input frequency becomes higher, the
pulse duty cannot maintain the 50±10% specification. Conduct derating on the maxi-
mum input frequency so that the pulse duty will be within the following specification
range.
<Derating computation formulae of open collector's maximum input pulse frequency >
0.8 / (Maximum input frequency x A) – Voltage rise time >= 3 x 10
A
Voltage rise time
Encoder exclusive pulse rise time (s) : Please inquire at the encoder manufacturer.
R (ohm) (Input resistance)
value
C (F) (Cable static capacity)
<Example>
Encoder
Cable
From Formulae (1)
0.8 / (Maximum input frequency x A) – Voltage rise time >= 3 x 10
Voltage rise time = (0.35 x 10
[Maximum input frequency] <= 87912 (Pulse/s) [Single phase input]
 The case of VEC007(Line Driver)
As for the PG feedback signals, Terminal A and NA are connected for Phase A, Terminal B
and NB are connected for Phase B.
The polarity of the pulse input signal should be as follows.
Non-inverting input side: A, B
Inverting input side: NA, NB
The signal feedback from the encoder should have the waveform shown in Figure
4-1 in terms of the motor rotation direction. The encoder installation direction and
signal wiring should be done accordingly.
* Forward rotation or reverse rotation is judged from the feedback pulses of Phase A
and Phase B (2-phase pulse that have 90 degrees of phase difference). Therefore, it
should be noted that, when connections are wrong, there is possibility for abnor-
mal rotation of the motor.
: IRS350-500 (SUMTAK), 2-phase input
Encoder pulse rise time: 0.35 x 10
: ROVV-SB-0.2-5P-10m (Furukawa Electric)
Static capacity: 120 x 10
–6
<= 43956 (Pulse/s) [Two-phase input]
: (single phase input: 2) (two-phase input: 4)
: Encoder exclusive pulse rise time + R x C
: Internal resistance 1000 (ohm) + external resistance
(in case there is external resistance)
: Please inquire at the cable manufacturer.
-6
(s)
–12
(F/m) x 10 (m)
-12
) + 1000 x (120 x 10
11
E6581319
–6
.....(1)
–6
-6
x 10) = 1.55 x 10
