Generac Power Systems CorePower 6/7 kW 60 Hz Diagnostic Repair Manual page 14

Section 1.2
Measuring Electricity
MEASURING CURRENT
Clamp-On
To read the current flow, in AMPERES, a clamp-on ammeter
may be used. This type of meter indicates current flow through
a conductor by measuring the strength of the magnetic field
around that conductor. The meter consists essentially of a
current transformer with a split core and a rectifier type instrument
connected to the secondary. The primary of the current transformer
is the conductor through which the current to be measured flows.
The split core allows the Instrument to be clamped around the
conductor without disconnecting it.
Current flowing through a conductor may be measured safely and
easily. A line-splitter can be used to measure current in a cord
without separating the conductors.
Figure 3. Clamp-On Ammeter
Figure 4. A Line-Splitter
Note: If the physical size of the conductor or ammeter capac-
ity does not permit all lines to be measured simultaneously,
measure current flow in each individual line. Then, add the
individual readings.
Page 12
PART 1
In-Line
Alternatively, to read the current flow in AMPERES, an in-line
ammeter may be used. Most Digital Volt-Ohm-Meters (VOM) will
have the capability to measure amperes.
This usually requires the positive meter test lead to be connected to
the correct amperes plug, and the meter to be set to the amperes
position. Once the meter is properly set up to measure amperes the
circuit being measured must be physically broken. The meter will be
in-line or in series with the component being measured.
In Figure 5 the control wire to a relay has been removed. The
meter is used to connect and supply voltage to the relay to
energize it and measure the amperes going to it.
1.00
BATTERY
- +
Figure 5. A VOM as an In-line Amp Meter
MEASURING RESISTANCE
The VOM may be used to measure the resistance in a circuit.
Resistance values can be very valuable when testing coils or
windings, such as the Stator and Rotor windings, or checking a
wire for an open or grounded condition.
When testing Stator windings, keep in mind that the resistance
of these windings is very low. Some meters are not capable of
reading such a low resistance and will simply read CONTINUITY.
If proper procedures are used, the following conditions can be
detected using a VOM:
• A "short-to-ground" condition in any Stator or Rotor winding, or
a short to ground on a specific control wire.
• Shorting together of any two parallel Stator windings.
• Shorting together of any two isolated Stator windings.
• An open condition in any Stator or Rotor winding, or an open in
a control wire.
GENERAL INFORMATION
A
RELAY