Maintenance And Inspection Procedure; Precautions; Measurement Of Mains Voltage, Current And Power - Hitachi L100 SERIES Service Manual

7. Maintenance and Inspection Procedure

7-1. Precautions

(1) Maintenance and Inspection Precautions
Be sure to check the followings before starting maintenance and inspection because there is a
danger of electrical shock.
Display on the digital operation panel and POWER indication has been turned OFF.
The voltage between + and - is 15Vdc or lower.
Discharging resistor (500 ohm 30W for 200V class, 1k ohm 60W for 400V class) has been
connected between + and - terminals for 15 seconds or more after main power had turned off,
(2) General Precautions
Always keep the unit clean so that no dust nor other foreign materials come inside of the
frequency inverter.
Pay attention to broken lines and faulty connections. Firmly connect terminals and connectors.
Keep frequency inverter away from moisture and oil.
Dusts, steel filings , swarf , and other foreign materials can damage insulation and causing
unexpected accidents/failure. Please pay attention to them.

7-2. Measurement of Mains Voltage, Current and Power

General measuring instruments for mains voltage, current and power are shown in Table 7-1.
The voltage to be measured is the effective value of fundamental wave, and the power to be measured
is the total effective value.
(1) Measurement of output voltage
Moving iron type instrument does not show accurate values for measurement of the output voltage.
Make measurements according to the method shown in Fig. 7-3 (table 7-1) or using the circuit
indicated in Fig. 7-1 and 7-2.
Frequency
Inverter
U
V
W
2W
220kohm
Diode
600V 0.1A or above (200V class)
1000V 0.1A or above (400V class)
Fig. 7-1. Output voltage measurement circuit (with load)
Motor
Load
Fundamental wave
+
effective value : V
V
DC
-
Moving coil type DC Volt meter
300V (200V class)
600V (400V class)
7-1
= V * 1.1
AC DC